Download Master thesis: Ecological measures of spatial memory

Ecological measures of everyday spatial memory – an
overview of everyday spatial memory problems, factors
of influence and assessment methods
Sarah Plukaard (0254819)
Utrecht University, the Netherlands
Supervisors:
Albert Postma & Maartje de Goede
Helmholtz Institute, Utrecht University, the Netherlands
Abstract
This review considers the use of everyday spatial memory, everyday problems with
spatial memory, the neurological and psychological causes of these problems, and
methods that can be used to assess everyday spatial memory. Everyday spatial memory
problems involve ‘getting lost’ or ‘forgetting where to find car keys’. Specific everyday
spatial memory problems are categorized into groups based on whether the problems
concern small or large scale, short or long term, and static or dynamic spatial memory.
Current evidence about the effects of age, gender, neurological damage, visual
impairments, stress and mood on spatial memory performance is reviewed. It appears that
age and hippocampal damage are factors that may influence all listed everyday problems,
whereas other factors such as visual impairments and mood may cause only specific
spatial memory problems. Everyday spatial memory can be measured by means of
surveys and questionnaires to obtain information from subjective reports. Experimental
research on everyday spatial memory behaviour can be carried out in virtual
environments (VEs) or in real world environments. The validity, advantages and
disadvantages of surveys, VE and real environment studies are discussed. Based on the
evidence provided by current studies and recent VE developments, we consider virtual
reality as the most appropriate and valid method to study everyday spatial memory.
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1. Introduction
Spatial memory is used to encode, store and retrieve spatial information. This cognitive
process is essential for simple everyday activities such as finding your way to the
supermarket and subsequently knowing where to find the milk. Spatial memory includes
the ability to remember the spatial layout of environments, to know how to travel from
one place to another, to remember the locations of objects, to know your own location in
the environment, to have knowledge about the general geographic environment, and
knowledge about spatial arrangements of objects. It is a complex multidimensional
process which includes a variety of components that help us to orient and act in space (cf.
Kessels, De Haan, Kapelle & Postma, 2001; Postma, 2005). Almost all everyday actions
require adequate spatial abilities and deficits in spatial memory may have great impact on
the quality of life. Even a simple action such as picking up one object (e.g. a glass of
water) requires spatial abilities: finding the object in space and judging the distance
between the glass and you hand. In everyday life, spatial memory is applied in different
environments, different situations and by different people with different spatial abilities.
For instance, spatial memory declines with age resulting in different spatial behaviour in
the environment by elderly people (e.g. Burns, 1999). Specific questions are: How is
spatial memory performance influenced by emergency situations or threatening
environments? Which problems do people with spatial memory impairments encounter in
everyday life? Which problems occur to all people in everyday spatial environments?
How can we improve spatial memory performance in different environments or different
situations? To answer these questions or to direct future research into answering these
questions, this review focuses on spatial memory in natural environments. The purpose of
this review is to present an overview of different forms of spatial memory, problems in
everyday spatial memory, neurological and psychological origins of these problems,
different methods to measure spatial memory in the natural environment, and the validity
of these methods.
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1.1. Taxonomy of spatial memory
As spatial memory is a complex function, different components of spatial memory can be
described which are necessary for different everyday actions. For instance when traveling
to the supermarket you need to know where to go (route learning) where you could rely
on knowing when to go left or right until you end up at the supermarket (response
learning) or on having a spatial layout of the neighborhood in your mind (cognitive map).
Before you leave, you require knowing where you left your car keys (object-location
memory) which could be located on top of the table to the left of (categorical coding) or
10 cm next to a magazine (coordinate coding). During the journey you constantly have to
update spatial information in order to orient yourself (spatial working memory), you have
to know where the supermarket is located relative to your own position (egocentric frame
of reference) or, when you have to take a detour, where the supermarket is relative to e.g.
the church (allocentric frame of reference).
For the majority of everyday activities you require spatial working memory. Spatial
working memory is part of working memory in general which is considered as a system
with two components: a ‘phonological loop’ which holds auditory and speech-based
information and a ‘visuo-spatial sketchpad’ which holds visual and spatial information.
These (slave) components are under attentional control of a ‘central executive’,
responsible for a.o. selective attention, inhibition, coordination and switching between
stimuli, tasks and retrieval strategies (Baddeley, 1996; Baddeley, 1998). The visuo-spatial
sketchpad which holds visual and spatial information thus includes spatial working
memory. Spatial working memory on its own involves the ability to keep spatial
information active for short periods of time in order to update or process this information
(Jonides, Smith, Koeppe, Awh, Minoshima & Mintun, 1993; Van Asselen, 2005). In
everyday life this form of spatial memory is required for all activities in which the
environment is changing. For instance during a walk from one place to another (e.g. from
your house to the supermarket) you require the ability to update spatial information with
almost every step you take in order to keep track of where you are in space. Furthermore,
in order to plan the route, you require holding spatial information active in memory so
you can decide where to go next.
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Traveling from one place to another does not just require spatial working
memory, but is distinguished as a form of spatial memory on its own as route learning or
spatial navigation (e.g. Postma, Jager, Kessels, Koppeschaar & Van Honk, 2004; Van
Asselen, 2005). Route learning includes way finding and navigating in familiar or new
environments. This form of spatial memory is essential for traveling from one place to
another (such as from your house to the supermarket) but also for finding your way inside
a building (e.g. inside the supermarket). It involves planning the route in advance and
continuous updating of your spatial knowledge (these are spatial working memory
functions) as the environment will constantly change during a journey. Different
strategies can be used for route learning. One strategy is generating a cognitive map of
the environment in memory in which the spatial lay-out of the environment is represented
in your mind (Bohbot, Iaria & Petrides, 2004; Van Asselen, 2005). This strategy involves
spatial learning where one learns the spatial relation between elements (i.e. landmarks) in
the environment. As such, you know for example the location of the supermarket in
relation to your house or your car. Another strategy is response learning (Iaria, Petrides,
Dagher, Pike & Bohbot, 2003; Bohbot et al., 2004; Van Asselen, 2005) in which a route
is learned through repetition of rewarded behaviours (e.g. you learn to turn left or right in
response to stimuli (e.g. at the post office) as it rewarded you by arriving at the
supermarket).
Furthermore, the everyday environment can be viewed from different frames of
reference: an egocentric or an allocentric frame of reference (Klatzky, 1998). An
egocentric (self/viewer-centered) frame of reference is used to code spatial information in
relation to the position of the observer whereas an allocentric (other/world-centered)
frame of reference is an external reference frame, independent of the viewer’s position.
An example of using an egocentric way of coding space is turning ‘left’ or ‘right’ as these
directions depend on the orientation of our own body. Another example is when you
point in a certain direction (e.g. to show someone else the location of the supermarket),
which also depends on your own location as someone else must point in a different
direction to appoint the same location. In addition, when pointing towards a certain
location, you need to have a spatial layout of the environment in your mind (cognitive
map) and to keep this information active until you perform the relevant action (spatial
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working memory). However, when you use a cognitive map for memorizing a route, you
are using an allocentric frame of reference since the relation between two landmarks does
not depend on our own position in space.
Another distinguished form of spatial memory is object-location memory. This is
used for memorizing specific locations for certain objects (Postma & De Haan, 1996;
Kessels et al., 2001). Object-location memory is essential in everyday life as you have to
remember for example where to find the milk in the supermarket or to recall where you
left your car keys. It includes three separate processes: memorizing the identity of an
object, memorizing the location of an object, and memorizing the relation between
identity and location (Postma et al., 2004). Furthermore, there are two representations to
code for the relation between two objects in space: categorical and coordinate spatial
relations (Kosslyn, Chabris, Marsolek & Koenig, 1992). When the spatial relation
between two objects is specifically encoded in terms of metric distances, one uses
coordinate representations. Kosslyn, Koenig, Barrett, Cave, Tang & Gabrielig (1989)
proposed that these representations are used to guide actions (e.g. to guide our eyes or
arm to move exactly towards an object). Alternatively, when spatial relations are assigned
to a category such as ‘above’ or ‘to the left of’, one uses categorical representations.
1.2. Brain areas involved in spatial memory
After giving an overview of different components of spatial memory, the question arises
whether these forms are functionally and neurologically distinctive or whether they are
part of the same system used in different ways. To further explore this issue, the current
paragraph presents an overview of evidence for brain structures associated with different
forms of spatial memory. The main structures that have been related to spatial memory
processes are the hippocampus, prefrontal cortex and posterior parietal cortex (cf. Van
Asselen, 2005).
The hippocampus has a major role in spatial memory (Burgess, Recce & O’Keefe, 1994)
and is involved in many functions of spatial memory (see Burgess, Maguire and O’Keefe,
2002 for a review). First of all, it contains pyramidal cells that are called ‘place cells’
because they are spatially coded (O’Keefe and Dostrovsky, 1971). O’Keefe and Nadel
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(1978) suggested that these place cells are each restricted to a portion of the environment.
The place cells fire when a rat is in a certain location within an environment, independent
of its orientation. This indicates that the hippocampus is involved in the processing of
spatial information from an allocentric frame of reference (O’Keefe and Dostrovsky,
1971; O’Keefe and Nadel, 1978) and is therefore thought to provide a cognitive map,
which is necessary for navigating in space. The concept of a cognitive map for way
finding comes from Tolman (1948), who suggested that this cognitive map indicates
routes, paths and environmental relationships. An fMRI study, conducted by Hartley,
Maguire, Spiers & Burgess (2003), confirmed that the hippocampus “provides a
cognitive map” (Hartley et al., 2003 – p. 885) since it showed activation when subjects
were accurately navigating via new routes.
Second, the hippocampus and the parahippocampal gyrus are associated with
object-location memory. That is, the right posterior parahippocampal gyrus has shown
activity during recognition of object locations (Johnsrude, Owen, Crane, Milner & Evans,
1999). Furthermore, patients with right parahippocampal or hippocampal lesions have
shown deficits in object-location memory (both recall and recognition was impaired)
(Bohbot, Kalina, Stepankova, Spackopva, Petrides & Nadel, 1998; Crane and Milner,
2004; Stepankova, Fenton, Pastalkova & Bohbot, 2004). However, Smith and Milner
(1989) found impairments in object-location memory in patients with right hippocampal
lesions only after a 4 minutes delay. Kessels, Hendriks, Schouten, Van Asselen & Postma
(2004) studied patients with amygdala and hippocampal lesions in either the right or the
left hemisphere. Patients lacking the left amygdala and hippocampus showed
impairments in object-location binding whereas patients lacking the right amygdala and
hippocampus showed impairments in coordinate positional memory. Considering the
large amount of different results concerning the left or the right hippocampus or
parahippocampal gyrus in object-location memory, the specific role of the hippocampus
in this component of spatial memory remains unclear.
Finally, the hippocampus is essential for encoding spatial information from
working memory into long term memory (e.g. Feigenbaum, Polkey & Morris, 1996;
Abrahams, Morris, Polkey, Jarosz, Cox, Graves & Pickering, 1999). Feigenbaum et al.
(1996) showed that the human right hippocampus is essential for the processing of spatial
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working memory (which was previously suggested by Olton and Feustle (1981) who
studied hippocampal function in rats). In addition, Abrahams et al. (1999) found deficits
in spatial working memory as well as spatial reference memory in patients with unilateral
atrophy in the right hippocampus.
The lateral prefrontal lobe is essential for working memory processes in general such as
updating and maintenance of information (Fletcher and Henson, 2001). The dorsal parts
of the lateral prefrontal cortex have mainly been related to keeping spatial information
active in memory (Nelson, Monk, Lin, Carver, Thomas & Truwit, 2000; Belger, Puce,
Krystal, Gore, Goldman-Rakic & McCarthy, 1998; Petrides, Alivisatos, Evans & Meyer,
1993; Jonides et al., 1993). For example, Nelson et al. (2000) studied the functional
organization of working memory in 8-11 year old children and found a.o. activation in
dorsal aspects of the frontal cortex during a spatial working memory task (whereas
ventral aspects showed activations during a non-spatial working memory task). They also
found that the activation area was somewhat larger in the right compared to the left
prefrontal cortex. These findings were consistent with findings in a study with adults who
performed the same spatial working memory task (Casey, Cohen, Craven, Davidson,
Irwin, Nelson, Noll, Hu, Lowe, Rosen, Truwit & Turski, 1998).
The posterior parietal lobes are engaged in both categorical and coordinate spatial
relations (Kosslyn, 1994; Kosslyn et al., 1989). As described above, categorical relations
between objects in space are defined by general, abstract codes. Since these categories
are language-related, Kosslyn (1994) suggested that the left cerebral hemisphere
(dominant for language processing in most right-handed people: Knecht, S., Dräger, B.,
Deppe, M., Bobe, L., Lohmann, H., Flöel, A., Ringelstein, E.B. & Henningsen, H., 2000)
might be specialized in processing categorical spatial relations. He also suggested that the
right cerebral hemisphere (associated with navigational processing (Kosslyn et al., 1989))
may be essential for coordinate representations. This lateralization has been confirmed by
psychophysical as well as brain imaging studies (see Jager and Postma (2003) for a
review). Using visual half field methods, Hellige and Michimata (1989) showed that
performance on categorical tasks was better when processed in the left hemisphere and
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performance on coordinate tasks was better when processed in the right hemisphere.
Neuroimaging has also revealed right hemisphere dominance in coordinate tasks and left
hemisphere dominance in categorical tasks (Baciu, Koenig, Vernier, Bedoin, Rubin &
Segebarth, 1999; Kosslyn, Thompson, Gitelman & Alpert, 1998). All activations were
found in parietal areas except for the Kosslyn et al. study (1998), in which left
hemispheric dominance for categorical tasks was found in frontal regions.
In addition, neural activity in posterior parietal lobes is also associated with
navigating through space (route learning) in VR, regardless of the strategy used
(cognitive map or response learning) (Aguirre, Detre, Alsop and D’Eposito, 1996; Iaria et
al., 2003; Spiers and Maguire, 2006). It has been suggested that these areas together with
the anatomically closely linked motor-premotor and supplementary motor areas (Petrides
and Pandya, 1984) are involved in higher-level control of movement through space
(Milner and Goodale, 1995; cf. Iaria et al., 2003). It has also been reported that medial
parietal regions are mainly involved in processing movement through immediate space,
whereas lateral parietal regions are mainly involved in planning movement through space
beyond instant view (Spiers and Maguire, 2006). Furthermore, the posterior parital cortex
has been reported to play a role in egocentric spatial processing (Burgess, Maguire and
O’Keefe, 2002) and spatial working memory (Rowe, Toni, Josephs, Frackowiak and
Passingham, 2000) which are both spatial memory components that are essential during
spatial navigation and route-learning.
The caudate nucleus has been related to response learning in rats (Packard, 1999;
Packard and McGaugh, 1996). Rats that received a glutamate injection (which stimulates
neural activity) in the caudate nucleus predominantly exhibited response learning as a
strategy for route learning (navigating), whereas rats that were injected in the
hippocampus predominantly exhibited place learning as navigation strategy (Packard,
1999). After blocking hippocampal activity, rats were still able to navigate correctly
through a maze, but used response learning instead of place learning as a strategy
(Packard and McGaugh, 1996). Using VR, caudate nucleus has also shown activation in
humans when participants used response learning as strategy during navigation (Iaria et
al., 2003). However, one may question whether this strategy actually is part of spatial
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memory or not as response learning may in fact be learning an association between a
body movement and a stimulus without further spatial information. On the other hand, it
can be argued that spatial orientation in relation to the stimulus (a landmark) is necessary
in order to make the appropriate body movement. In light of this statement, responselearning can be observed as part of spatial memory as it requires the appropriate spatial
knowledge (e.g. determining your own location in relation to a landmark) and the
appropriate spatial action (e.g. turning left or right).
2. The organization of everyday spatial memory problems
Since spatial memory plays such a major role in everyday life, small failures in spatial
memory may have great impact. Most people regularly encounter slight spatial memory
failures in everyday life. An example is losing your car keys or forgetting where you
parked your car in a large parking lot (object-location memory). Another everyday
problem is getting lost in buildings, where people have forgotten how they got to a
certain point (route learning) and feel disoriented (cognitive map). Furthermore, some
people have problems with converting spatial information from a 2D route map into the
3D real environment (cognitive map, spatial working memory). Other problems concern
pointing towards locations that are out of view or giving other people route directions
(cognitive map / allocentric representations), estimating distances (coordinate spatial
relations) or to recall whether the bakery was above or below the post office in a three
store shopping mall (categorical relations). Different types of everyday spatial memory
can be distinguished. That is, spatial memory problems can occur over large scale or
small scale areas, in short or long term storage, and in a static or dynamic environment.
By combining these different types, everyday spatial memory problems can be
subdivided into eight different groups:
1. large scale – short term – static
2. large scale – short term – dynamic
3. large scale – long term – static
4. large scale – long term – dynamic
5. small scale – short term – static
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6. small scale – short term – dynamic
7. small scale – long term – static
8. small scale – long term - dynamic
Furthermore, a distinction can be made between prospective and retrospective spatial
memory. With this distinction, the spatial memory problems that are organized into these
eight different groups could each be either prospective or retrospective. The next
paragraphs explain the content of each type of spatial memory problems.
Large and small scale
Spatial memory can cover small (within one room) as well as relatively large areas
(including neighborhoods or even cities and countries). Getting lost on the way from your
house to the supermarket, inside buildings or in unfamiliar cities are examples of large
scale spatial memory problems. These actions rely on spatial knowledge that covers
relatively large areas. We consider space which is larger than can be observed instantly
from one single viewpoint as large-scale space (as put forward by Kuipers, 1978). It
takes time to gather spatial information about large-scale space by moving through the
environment and to put information from multiple viewpoints together to construct a
large-scale cognitive map or large-scale route information. Dysfunction in specific forms
of spatial memory such as spatial working memory, allocentric spatial ability, or
generating a cognitive map may hamper the construction of one single mental layout of
space from small pieces of spatial information. This may therefore cause problems with
using spatial memory over a large-scale area.
Small-scale (or table-top) spatial memory covers information about an area that
can be viewed instantly from one single viewpoint such as the spatial layout of the living
room or the spatial organization of objects inside a cupboard. Forgetting were you put
certain objects can therefore be seen as a small-scale spatial memory problem. Objects in
small-scale areas are generally seen as more manipulable (they can be touched and
moved) as contrasted with objects in large-scale space (cf. Hegarty, Montello,
Richardson, Ishkawa and Lovelace, 2006). This allows people to gather more detailed
information about objects in small-scale space. In everyday life, people recall specific
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locations for specific objects, such as a particular teacup which is located in the left
kitchen cupboard and the car keys that are in the second drawer underneath the yellow
notebook et cetera. However, problems with processing spatial information from an
egocentric frame of reference or object-location memory may cause problems in smallscale spatial environments.
An example of integrating small-scale spatial memory with large-scale spatial
memory is reading a route-map and subsequently finding your way in the natural
environment. This regularly performed action involves converting spatial information
from a small-scale 2D map into navigating through a large-scale 3D environment. Some
people have problems with map-reading or with converting 2D map information into the
3D natural environment. One might wonder whether this regularly performed spatial
action is supported by one system or an integration of two systems for different spatial
scales. Hegarty et al. (2006) describe several studies in which it is claimed that both
abilities are completely overlapping (the unitary model) or, in contrast, completely
dissociated (the total dissociation model). In their own study, they found that small-scale
spatial abilities predicted performance on large-scale performance to some extent. Based
on these findings they suggested that there should be at least partial overlap between
small and large-scale spatial memory.
Short and long term
Spatial information can be stored in memory for a short period of time (for example in
order to be used just once) or for a longer period of time. We label this short term and
long term spatial memory respectively. Whether spatial information is stored for short or
long periods of time depends on the purpose for which it is needed. If an observer aims to
construct a mental layout (cognitive map) while navigating through a new environment,
spatial information is aimed to be stored for a long period of time. In addition, when
objects are to be stored for longer periods of time, this object-location information should
be available for a long period and therefore requires being stored in long term spatial
memory. When individuals are unable to process spatial memory from short term into
long term memory or when functions such as generating a cognitive map or object-
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location memory are disrupted, one could encounter problems in using spatial memory
for a longer period of time.
If you forget which route you just followed in a familiar environment or if you get
disoriented fairly easily in new environments, you may have trouble with keeping
detailed spatial information active for a short amount of time. Short term spatial memory
can specifically be used to remember the exact route you followed during route-learning
or navigation. This information may be essential for a short period of time (e.g. in a new
environment: to be able to find your way back), but irrelevant to keep in memory for a
longer period (when a mental construct of the environment is available and you can find
your way back based on a mental layout or when you will not enter the same environment
another time). Some object-locations are stored only for a short time in memory: e.g.
when objects have a temporary location for instant use (you moved the milk from the
fridge to the table only during breakfast). It is irrelevant to store this object-location
information for longer periods of time (ordinarily, you can find the milk in the fridge and
you do not have to know its specific location on the table during breakfast).
Static and dynamic
Another distinction which can be made in everyday spatial memory is between static and
dynamic use of spatial memory. We consider spatial memory as static when spatial
information content is fixed and when it does not involve environmental changes,
sequential information or updating of spatial knowledge. A static view of environmental
space is associated with mainly an allocentric survey-based ‘from above’ perspective (cf.
Postma et al., 2004). An example of problems with static spatial memory is the inability
to recall where you left your car keys. It involves finding a stationary object in a fixed
environment. To know the relative distance between your house and the supermarket is
another example of static spatial memory in the natural environment. Hence, static spatial
memory includes object-location memory, knowledge about spatial distances, and
knowledge about the spatial lay-out of environments (either small or large-scale).
Spatial memory is considered dynamic when it employs changes in the
environment, sequential spatial information, planning and updating of spatial
information. Postma et al. (2004) put forward that dynamic spatial memory often engages
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a ‘from within the environment’ perspective (which mainly involves egocentric
representations of space). Getting lost when you travel from one place to another (which
constantly requires locating yourself in the environment, updating spatial knowledge
about the changing environment, and planning the route ahead) is an example of
problems with dynamic spatial situations. It involves sequences of different spatial
environments as well as sequences of spatial decisions. Another everyday example is
giving someone else route directions in which you have to mentally walk through the
environment. This involves similar dynamic use of spatial memory as when you are
traveling through the environment yourself. Problems with spatial working memory,
response learning or route-learning may therefore disrupt the dynamic use of spatial
memory (or the use of spatial memory in dynamic situations).
Prospective and retrospective
Spatial memory can be used to look forward in time (prospective) or to recall previous
spatial information (retrospective). Prospective spatial memory involves planning in
advance and having expectations about future spatial situations. When you are traveling
from one place to another or navigating through a building, you plan the route in advance
in order to know when to turn left and right before arriving at your destination. You have
an expectation about the consequences of each action: e.g. when you turn left at the post
office you expect to get closer to the supermarket. When navigating through a new
environment you also plan to take the best route and have expectations about future
spatial situations although you do not have an exact mental image of the spatial layout.
In a new building for example, when you climb the stairs you may expect that the next
floor will have a similar floor plan as the former one and thus you expect to be able to go
left when you get upstairs. Several studies have examined route-planning behaviour in
humans (e.g. Elliott, Frith and Dolan, 1997; Maguire, Frackowiak and Frith, 1996; Spiers
and Maguire, 2006). Spiers and Maguire (2006) for example studied route-planning
behaviour of taxi drivers in a highly accurate computer simulation of a real-world
environment (the city of London, UK). Using fRMI they reported several brain areas (a.o.
the hippocampus, retrosplenial cortex and posterior parietal cortex) that were activated
specifically during route-planning. Another example of using prospective spatial memory
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is when you are planning where to store certain objects (e.g. you plan where you are
going to leave your car keys in order not to lose them next time). In addition, when you
move objects to make room for others you have to predict how much space will be
available when you remove something. This involves a prospective view of the spatial
layout of the environment. We suggest that prospective spatial memory mainly requires
spatial working memory (planning) but also the ability to generate allocentric cognitive
maps about the spatial layout since you have to make predictions about a spatial
environment beyond the current view.
Retrospective spatial memory involves the ability to recall previous spatial
information. This involves keeping track of where you are in a new environment (of
which you have not constructed a cognitive map yet), of where you left certain objects in
space, or to recall the spatial layout of the parking space (in order to find your car back).
Retrospective spatial memory is used to remember the spatial layout of where you have
been or the route that you have followed (whilst planning where to go next). Studies in
which subjects are required to retrace a previously traveled route (e.g. Cherrier,
Matsumoto, Amory, Asthana, Bremner, Peskind, Raskind and Craft, 2005; Van Asselen,
Fritschy and Postma, 2006) or in which subjects are asked to recall object-locations (e.g.
De Goede and Postma, 2008; Postma, Kessels and Van Asselen, 2008 (review)) are
examples of measuring retrospective spatial memory. Everyday problems in retrospective
spatial memory occur when people forget where they left certain objects or how they got
to a certain location. An evident example of relying on retrospective spatial memory is
when you have lost something during a journey from one place to another and you have
to follow the exact same route back.
To conclude this chapter, everyday spatial memory problems can be organized into eight
different groups. A spatial memory problem is assigned to a certain group based on
whether the problem involves either large or small scale areas, short or long term storage
and static or dynamic environments. ‘Forgetting where you left your car keys’ for
example could be assigned to group 5 (small scale – short term – static) or group 7 (small
scale – short term – static) depending on how long the keys where in a certain location.
This problem would also be a retrospective spatial memory problem as it involves the
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ability to recall previous spatial information. Problems with giving route directions or
with planning a route in a familiar environment would fit into group 4 (large scale – long
term – dynamic) as it covers large scale spatial information that is stored in long term
memory involving changes in the environment and sequences of actions. Furthermore,
this problem is a prospective memory problem as it involves planning and expectations
about future spatial environments.
3. Underlying factors of everyday spatial memory problems
Most people encounter problems with several aspects of spatial memory to a small extent
in everyday life. However, some people encounter spatial memory problems to a larger
extent than others. To answer the question why some people have more spatial memory
problems than others, several neurological and psychological factors that may cause
problems with everyday spatial memory are summed up in this chapter.
3.1. Age
It is generally known that memory weakens with age. These impairments mainly involve
spatial problems as one of the first things that elderly people complain about is losing the
ability to navigate in new environments (Burns, 1999). As a result, elderly people start to
avoid unfamiliar routes and places.
Animal studies have confirmed that spatial memory grows weaker with age (see
Barnes, 1988 for a review). These age-related deficits in spatial tasks (such as place
learning or route learning) have mainly been associated with hippocampal changes: such
as increased decay in long-term potentiations (Bach, Barad, Son, Zhuo, Lu, Shih,
Mansuy, Hawkins and Kandel, 1999; Barnes and McNaughton, 1987) and a decrease in
accuracy of information processing of older hippocampal neurons (Barnes, Rao and
McNaughton, 1987; Barnes, 1988). In humans, aging is in general associated with
memory impairments. A common characteristic of age-related diseases as for instance
Alzheimer’s, is that elderly people get lost even in familiar environments. However, also
normal aging (i.e. excluding age-related diseases) has been associated with increased
impairments on all spatial memory components. A variety of studies illustrate that older
healthy adults perform poorer than young adults on tasks that require spatial working
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memory (e.g. Salthouse, Babcock and Shaw, 1991), route learning (e.g. Kirasic and
Mathes, 1990; Kirasic, 1991; Kirasic, Allen and Haggerty, 1992; Wilkniss, Jones, Korol,
Gold and Manning, 1997; Moffat, Zonderman and Resnick, 2001), and object-location
memory (e.g. Cherry and Park, 1993; Schiavetto, Köhler, Grady, Winocur & Moscovitch,
2002). Memory impairments associated with aging mainly involve allocentric spatial
memory: remembering spatial relationships between landmarks and objects in large
environments as well as learning a route from a map is impaired with age (cf.
Rosenzweig and Barnes, 2003; Moffat, Elkins and Resnick, 2006). Moffat and Resnick
(2001) for instance, studied the effects of aging on navigation and the use of a cognitive
map using virtual reality (VR). They demonstrated that the performance of old adults on
this route learning task was impaired compared to young adults. In a follow-up study,
they demonstrated that normal aging is associated with traveling longer distances to
locate the goal, spending less time to navigate the environment and impairments in
constructing a cognitive map (Moffat and Resnick, 2002).
Many age-related changes in a healthy human brain are initially observed in the
hippocampal area (Tomlinson and Henderson, 1976; Lupien, Leon, Santi, Convit,
Tarshish, Nair, Thakur, McEwen, Hauger and Meaney, 1998; Grady, McIntosh and
Craik, 2003; Maguire and Frith, 2003). This is in line with age-related memory problems.
Since the hippocampus is involved in the majority of spatial memory components, the
hippocampal age-related changes may explain the variety of spatial memory problems in
elderly people. Furthermore, neuroimaging has revealed that during spatial navigation,
elderly people show reduced activity in the hippocampus and parahippocampal gyrus, but
increased activity in anterior cingulate gyrus and medial frontal lobe in comparison to
younger people (Moffat et al., 2006). Increased activity in these frontal areas may
indicate that older adults show compensatory shifts in neural activity or that the
navigation task was more demanding for aged people. Moreover, several other studies
found functional as well as structural changes within the prefrontal cortex (ReuterLorenz, Jonides, Smith, Hartley, Miller, Marshuetz and Koeppe, 2000; Tisserand and
Jolles, 2003), which may be related to either a compensatory shift in neural activity (i.e.
the same memory system taken over by different brain areas) or with the use of different
strategies to encode space.
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3.2. Gender
Research on human sex differences in spatial memory is increasing (Postma et al., 2004).
In contrast to the general agreement that men are superior on spatial memory, there is no
such thing as one unitary superior spatial memory system. As described in chapter one,
spatial memory consists of multiple components which are together as well as
independently essential for multiple everyday activities. The question is: to what extent
do men outperform women or do women outperform men with regard to spatial memory?
And which everyday memory problems could be attributed to sex-differences? Several
studies, using the Corsi Block-Tapping task, demonstrated that men have a larger spatial
working memory span compared to women (Orsini, Chiacchio, Chinque, Cocchiaro,
Schiappa and Grossi, 1986; Capitani, Laiacona and Ciceri, 1991). In contrast, a study by
Postma et al. (2004) revealed no sex differences while using the same task, but a smaller
number of subjects. This indicates that the sex-differences on spatial working memory
may be relatively small. On a route learning experiment, men outperformed women on
learning a route on a map and on remembering metric properties, whereas women were
able to recall more of the landmarks (Galea and Kimura, 1993). This may indicate that
women may use different strategies to move around in everyday life (such as relying on
specific landmarks) than men (generating a cognitive map of environmental layout whilst
ignoring environmental details/landmarks). A study by De Goede, Berthoz, Zaoui and
Postma (submitted) showed that this difference in strategy was not the result of inabilities
in processing geometric cues in women, as men and women performed equally on
pointing towards a start position in the absence of visual landmarks during encoding as
well as retrieval. In a virtual environment, men were faster than women at finding their
way out of a complex, three-dimensional maze (Grön, Wunderlich, Spitzer, Tomczak and
Riepe, 2000). However, studies in natural environments revealed no such differences
(Worsley, Recce, Spiers, Marley, Polkey & Morris, 2001; Lewin, Wolgers & Herlitz,
2001; Lawton & Charleston, 1996) except for Silverman, Choi, Mackewn, Fisher, Moro
& Olshansky (2000) who found an advantage for men to navigate through a wooded area.
This indicates that in most natural environments, women do not encounter more problems
with route finding than men. Furthermore, women have shown superiority in several
17
object-location tasks: i.e. recognizing objects that have exchanged position (Eals and
Silverman, 1994; James and Kimura, 1997) and the legendary game Memory (McBurney,
Gaulin, Devineni and Adams, 1997). This superiority was confirmed by a recent metastudy (Voyer, Postma, Brake and Imperato-McGinley, 2007). In contrast, men have
shown superiority in object-location memory for nonsense objects (inkblots) (Lewin et
al., 2001) as well as identical objects (Postma, Izendoorn and De Haan, 1998). This
indicates that men outperform women on positional memory (without object
identification). These findings are consistent with findings on spatial memory tasks that
require coordinate coding of space such as an advantage for men in estimating distances
(Postma et al., 2004). In a recent study by De Goede and Postma (2008), women
appeared to outperform men in overall object location memory, whereas similar
performance for men and women was found on isolated object identity memory and
object-location binding.
Postma, Winkel, Tuiten and Van Honk (1999) revealed that sex-related
differences in spatial memory may be influenced by sex hormones as females performed
better in the nonmenstrual phase compared to during menstruation. fMRI has revealed
different patterns of activation for men and women during a virtual maze task: distinct
activation in the left hippocampus in males and increased right parietal and right
prefrontal activity in females (Grön et al., 2000). In a different fMRI study using a spatial
task (judgment of line orientation) showed bilateral activation in lateral frontal and midtemporal regions in men whereas this activation was restricted to the right hemisphere in
women (Gur, Alsop, Glahn, Petty, Swanson, Maldjian, Turetsky, Detre, Gee & Gur,
2000). This suggests that differences in lateralization may underlie sex differences on
spatial memory performance.
3.3. Neurological damage
As described in chapter 1.2., focal lesions can impair spatial memory abilities. Specific
lesions in specific brain areas cause problems in particular spatial memory components
and therefore in particular everyday spatial actions. Lesions in the hippocampus for
example have been associated with impairments in object-location memory (Smith and
Milner, 1989), object-location binding and coordinate positional memory (Kessels et al.,
18
2004), and spatial working memory (Abrahams et al., 1999). These specific lesions
should therefore mainly disrupt everyday spatial abilities in a static environment or in an
environment that requires a static mental representation of space such as relocating car
keys or the car in a parking lot, or judging the exact location of objects in space, and
reaching and grasping for these objects. Lesion in the hippocampus may cause
impairments in small scale areas, but will certainly impair large scale mental
representations as the hippocampus is essential for building a cognitive map (Hartley et
al., 2003). Lesions in dorsolateral prefrontal cortex are found to impair spatial working
memory (e.g. Bechara, Damasio, Tramel and Anderson, 1998) and may therefore impair
behaviour in dynamic environments (or in environments that require dynamic spatial
representations) and behaviour in environments that require prospective spatial memory
(which involves a.o. planning of future spatial actions and situations).
Neurodegenerative disorders such as Alzheimer’s dementia and Parkinson’s
disease are related to neuronal loss in a variety of areas (Panegyres, 2004). Alzheimer’s
disease is the commonest form of neurodegenerative disorders and has mainly been
associated with spatial memory deficits (De Tolledo-Morrell, Dickerson, Sullivan,
Spanovic, Wilson and Bennett, 2000; Kohler, Black, Sinden, Szekely Kidron, Parker,
Foster, Moscovitch, Wincour, Szalai and Bronskill, 1998), which are correlated with
Alzheimer related hippocampal atrophy. Alzheimer’s patients will therefore encounter
most problems with getting lost due to impairments in generating or using a cognitive
map. These patients will even get lost in familiar environments. Parkinson’s disease may
be associated with deficits in spatial working memory and memory for object locations as
a result of neuronal atrophy in prefrontal cortex, dopaminergic pathways and striatalfrontal circuits (cf. Panegyres, 2004). Parkinson’s disease patients may therefore
encounter more problems with losing objects and with the majority of everyday activities
that require spatial working memory such as traveling (which causes the environment to
change and which therefore demands the ability to update spatial information).
3.4. Visual impairments
Visual impairments alter behaviour in the natural environment and influence the
development and use of spatial memory. The main visual impairment associated with
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spatial memory problems is total blindness, but other visual impairments such as lowvision or monocular vision may also affect everyday spatial memory. In sighted people,
the generation of spatial representations through auditory experience still requires the
visual system (Zwiers, Van Opstal and Cruysberg, 2001) and tactile stimuli are typically
remapped in coordinates that are modulated by vision (Hötting, Rösler and Röder, 2004).
These studies demonstrate that vision is the primary sensory modality of spatial cognition
(see also: Eimer, 2004) and the loss of vision should have major impact on everyday
spatial memory (for a review on impaired spatial cognition in visually impaired
individuals see: Cattaneo, Vecchi, Cornoldi, Mammarella, Bonino, Ricciardi and Pietrini,
2008). Research has shown that early blind people have specific problems with spatial
processes that require active integration and transformation, whereas passive storage of
spatial information is similar to sighted people (Cornoldi and Vecchi, 2000). Pasqualotto
and Newell (2007) found that the updating of a haptically learned spatial environment is
impaired in blind people. Noordzij, Zuidhoek and Postma (2006) demonstrated that blind
individuals generate a route-based representation of the environment instead of a surveybased cognitive map in sighted people. This finding implicates that blindness can make
moving through the environment less flexible (when a route is blocked, it would be
difficult to find an alternative route without knowledge of the spatial layout). This finding
also implicates that blind people mainly rely on egocentric response learning and that
their spatial memory largely contains dynamic spatial information. In addition, blind
people perform poorly on other survey based spatial tasks such as estimating Euclidean
distances between locations (Rieser, Lockman and Pick, 1980) and pointing towards
locations in a room (Rieser, Guth and Hill, 1986). However, studies using tactile maps
indicate that survey-based representations do exist in blind individuals (Espinosa, Ungar,
Ochaita, Blades and Spencer, 1998) and that blind people can even outperform sighted
people on survey-based tasks (Tinti, Adenzato, Tamietto and Cornoldi, 2006). This
signifies that blind individuals are very well able to convert small-scale spatial
information on a map into large-scale 3D natural environmental space.
One can imagine that visually impaired people who suffer from severely reduced
visual capacity and require external devices to manage everyday activities may also be
impaired on spatial memory. However, visually impaired children and adults performed
20
better than blind children and adults on a variety of spatial tasks (Bigelow, 1996; Blanco
and Travieso, 2003; Byrne and Salter, 1983). Moreover, their performance was similarly
to sighted people (Bigelow, 1996; Blanco and Travieso, 2003; Vecchi, Cattaneo,
Monegato, Pece, Cornoldi and Pietrini, 2006). Only one study by Passini, Proulx and
Rainville (1990) showed that visually impaired individuals may show selective
impairments on route inverting, choosing shortcuts and mental rotations due to the
inability to use distant cues and visual reference points. Overall, findings on visually
impaired individuals suggest that the brain can use poor quality visual information to
generate adequate cognitive maps with appropriate visual layouts in spatial memory
Monocular vision is associated with reduced perception of depth as a result of
absent stereoscopic vision (Von Noorden, 1996). This affects a.o. depth judgments,
reaching, balance and orientation (Howard, 2002). These inabilities may also influence
spatial memory. Vecchi et al (2006) showed that monocular individuals were to a similar
extent as blind individuals impaired on an object-location memory task that required
imagery. Further research should clarify to what extent monocular vision may affect
specific everyday spatial memory abilities.
3.5. Stress and anxiety
Another factor that is known to influence spatial memory is stress or anxiety. Research
on animals revealed that chronic exposure to stress leads to decreased dendrites,
decreased length of dendrites, and cell loss in the hippocampus (Watanabe, Gould and
McEwen, 1992; Woolley, Gould and McEwen, 1990; Uno, Tarara, Else, Suleman and
Sapolsky, 1989). Luine, Villegas, Martinez and McEwen (1994) demonstrated that
chronic stress also leads impairments in hippocampal function: spatial memory
performance was reversibly weakened. Diamond, Fleshner, Ingersoll and Rose (1996)
showed that psychological stress impairs spatial working memory as rats exposed to
stress performed poorly in novel environments. In humans however, research on stress
has not shown obvious impairments in spatial memory. Schwabe, Oitzl, Philippsen,
Richter, Bohringer, Wippich and Schachinger (2007) studied the influence of stress on
spatial learning and discovered that psychosocial stress prior to learning reduces the use
of spatial learning strategies: stressed participants switched to stimulus-response
21
strategies more often than controls. This implicates that stressed individuals favor the use
of caudate nucleus-dependent strategies over strategies that require the hippocampus
(which is in line with animal studies that show stress-induced impairments of
hippocampal function). Whether this stress-related change in spatial learning strategy is
the result of decreased hippocampal function is not clear. A recent study revealed that
chronic stress (in addition to acute stress) increased the use of stimulus-response
strategies instead of spatial strategies in mice as well as humans (Schwabe, Dalm,
Schächinger and Oitzl, 2008). In a study carried out by Lawton (1994) an indirect
relationship was found between spatial ability and spatial anxiety: the use of an
orientation strategy (maintaining a sense of your own position relative to environmental
landmarks) instead of a route strategy was positively correlated with spatial perception
and negatively correlated with spatial anxiety. Furthermore, Schmitz (1997) found gender
differences in spatial memory performance which could be explained to a certain extent
by different levels of anxiety and fear: girls (who scored higher on anxiety and fear scales
than boys) moved more slowly through a maze, recalled more landmarks and fewer
directions than boys. Furthermore, all subjects (i.e. boys and girls) who scored high on
fear and anxiety showed similar results, although not completely significant.
Hence, stress and anxiety could impair spatial ability to a certain extent. In
humans, the influence of stress on behaviour in space is mainly expressed in the use of
non-spatial strategies which implicates specific impairments or at least cognitive
restrictions on spatial memory.
3.6. Mood
A small amount of studies have focused on the influence of mood on spatial memory.
However, if emotional state affects spatial memory performance, one can imagine that if
navigation or route finding in emergency situations is impaired, the consequences may be
catastrophic. Miller, Fujioka, Chapman and Chapman (1995) revealed that spatial
performance on a positional task (remembering the positions of dots in a display) was
impaired in participants with major depression. In addition, Tucker, Hartry-Speiser,
McDougal, Luu and deGrandpre (1999) found that subjects high in negative arousal did
not show a right hemisphere advantage for spatial processing (using visual half-field
22
methods) which was present in subjects with normal arousal levels and which is in line
with a right hemisphere dominance for spatial attention (Corbetta, Miezin, Shulman and
Petersen, 1993). Subjects with high negative arousal levels also showed an altered pattern
in EEG response to spatial stimuli. This indicates that emotional state may alter spatial
memory or the use of spatial memory. Brunyé, Mahoney, Augustyn and Taylor (in press)
are the first to report that high arousal states, either positive or negative, amplify the
symbolic distance effect (Moyer, 1973) in which the distance between two landmarks that
are relatively far away from each other are judged with faster response times and higher
accuracy compared to the distance between two landmarks that are relatively close
together. Subjects that studied a map in high arousal states performed better on judging
global spatial relations relative to controls, which indicates that high arousal may
improve the development and subsequent use of spatial memory. Subjects that studied the
map in low arousal states performed poorly on distal comparisons relative to both
controls and subjects inv high arousal states. Furthermore, low arousal levels did not
improve judgments about the distance between proximal landmarks which indicates that
low arousal may impair either spatial attention or spatial memory or both (Brunyé et al.,
in press).
To summarize, in the above chapter we have reviewed a large amount of literature
demonstrating that several factors such as age, gender, lesions, blindness and even
psychological factors such as stress, anxiety and mood may alter spatial memory and may
cause specific problems in the use of spatial memory in everyday life. To measure
exactly which problems occur in everyday life and to what extent specific impairments
cause everyday problems, future research should focus more on spatial memory
impairments caused by factors described above in ecological settings (i.e. natural or close
to natural environments).
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4. Measuring spatial memory in everyday life
As moving through the everyday environment or recalling spatial information about your
natural surroundings involves combined functioning of numerous components of spatial
memory, one might wonder whether laboratory studies measure spatial memory as it is
used in everyday life. In laboratory research, specific components of spatial memory can
be studied in isolation whereas in everyday life, spatial memory will always be applied in
a multidimensional way, using different components of spatial memory combined to get
the most effective results. Furthermore, the natural environment is usually much more
complex than laboratory spatial situations by, for instance, providing much more stimuli
(visual as well as auditory and vestibulo-tactile) which can either facilitate or impede the
use of spatial memory. To explore spatial memory in everyday life, one could study
people’s personal experiences with spatial memory problems, specific forms of spatial
memory in experimentally controlled virtual environments, or specific forms of spatial
memory in ecologically valid natural environments. In this chapter, an overview is
presented of these three measures and how each measure might contribute to knowledge
about everyday spatial memory use and problems. Furthermore, the construct validity,
external validity and internal validity of each measure is discussed.
4.1. Survey research / questionnaires
Surveys or questionnaires are a suitable method to obtain a large amount of data from a
large number of people. It is a structured set of questions to gather information from a
group of people about their experiences, beliefs, values or tendencies to act. It could give
an overview of problems that are experienced in everyday life and how spatial memory is
applied in the natural environment. Surveys could also measure which strategies are used
in different environments or situations, how frequently specific problems occur in
everyday life, or how people cope with these spatial memory problems. Questionnaires
on spatial memory are regularly used to measure the extent to which dementia or
Alzheimer patients encounter problems in the everyday spatial environment with the aim
to enhance the development of effective interventions, of adequate residential
environments or to improve their wayfinding efficiency (c.f. Chiu, Algase, Liang, Liu &
Lin, 2005; Wilson, Cockburn, Baddeley and Hiorns, 1989). Other examples of
24
questionnaires that measure everyday memory performance are the Inventory of
Everyday Memory Experiences by Hermann and Neisser (1978), the Cognitive Failures
Questionnaire by Broadbent, Cooper, Fitzgerald and Parkes (1982), and the Head Injury
Postal Questionnaire by Sunderland, Harris and Gleave (1984).
Construct validity: Construct validity concerns the adequacy of the independent
and dependent variables in a study. In a questionnaire one may question whether different
items are the best ones to measure specific forms of spatial memory. One may also
question whether questions are the best method to measure how everyday spatial memory
is used in everyday life. However, questions are the best way to measure someone’s
personal experience with everyday spatial memory problems. It could also contain many
items which results in a fairly broad view on these problems and may therefore include
problems that may not occur during specific experimental tasks.
Internal validity: The major problem with memory questionnaires is that
responding to items in itself is a memory task and that they are based on the participant’s
metamemory (which would most certainly become a problem for patients with memory
impairments). Will a person’s subjective report give an objective image of spatial
memory performances (e.g. do some spatial memory problems have more impact on a
person’s life and may therefore be rated as occurring more frequently than in reality)?
Questionnaires may thus be susceptible to biases such as responding as subjects feel they
should instead of what they truly believe or judging the frequency of certain problems
wrongly as a result of the impact of a certain spatial problem. Another problem with
questionnaires is that subjects may give incorrect responses as they cannot accurately
judge their spatial memory abilities (Herrmann, Grubs, Sigmundi and Grueneich, 1986).
However, questionnaires can be constructed to avoid these problems. An example is
using closed and very specific questions instead of open questions. If explicit examples
are used and specific answers are required (e.g. on frequency questions explicit numbers
per day, week or month can be enforced), a person can be guided towards the most
realistic answers. Furthermore, multiple items can be used that measure the same aspect.
Whether these questions actually measure the same aspect can be tested by means of
factor analysis as carried out for example by Chiu et al. (2005) on a newly developed
25
Everyday Spatial Questionnaire for Dementia patients or by Wilson et al. (1989) to test
the validity of the Rivermead Behavioural Memory Test.
External validity: As questionnaires can be completed by a broad range of people
and questions are fairly unlimited, the findings can quite easily be generalized to larger
populations and different environments. The only problem that might occur in ecological
validity (i.e. the relevance for everyday cognition and activities) is that participants may
be biased and their answers may not equal their everyday spatial actions. This problem
arises because questionnaires do not measure behaviour directly, but they measure how
people judge their own spatial behaviour. However, as described above, questionnaires
can be constructed to avoid these problems.
Hence, the construct and external validity of surveys are quite good, but the internal
validity may be at risk. Items that are well constructed (which are appropriate, detailed
and clear) may enhance the internal validity. Furthermore, data from questionnaires with
closed questions are well quantifiable: items that are rated on a scale provide numbers as
data which are easily used for analyses.
4.2. Virtual Environments
An increasing amount of studies use 3D virtual environments (VE) to investigate human
spatial memory in everyday environments. Virtual reality can be used to create a realistic
simulation of the natural everyday environment in which a person can navigate, follow
routes, move back and forth, and make 360 degree turns. Hence in a VE, a person can
perform similar spatial behaviour as in the real-world environment. A VE can resemble
the interior of a building, streets in a city or some other outside environment with as
many landmarks, road obstructions or other objects and situations that can be
encountered in the real world. Along with trainings for various occupations such as
drivers (Mahoney, 1997), pilots (Lintern, Roscoe, koonce and Segal, 1990), and soldiers
(Goldberg, 1994; Goldberg, and Knerr, 1997), VEs are used to assess spatial abilities of
patients with cognitive impairments for rehabilitations purposes (Brooks and Rose, 2003)
or to study spatial memory in general (Hurlebaus, Basten, Mallot and Wiener, 2008;
Maguire, Burgess and O’Keefe, 1999; Maguire, Spiers, Good, Hartley, Frackowiak and
26
Burgess, 2003). Hurlebaus et al. (2008) for instance, studied route learning strategies in a
complex and cluttered VE. The VE lacked unique landmarks or road networks, and the
only distal cues were four large coloured columns. They discovered strong differences in
route learning strategies between individuals with some participants being conservative
and others showing high variability in their route choices. The conservative participants
could reproduce the route without local landmarks and thus relied on metric information
whereas participants who showed high variety in route choices strongly relied on the
global landmarks.
Construct validity: The construct validity in VEs can be very good. To measure
for example route learning in an unfamiliar environment, this VE can be created and
participants can navigate in a similar way as in real life. Hence, the appropriate
environment can be constructed to measure the appropriate form of spatial memory or
everyday problem.
Internal validity: The main advantage of a VE is that the environment, as
contrasted with the real-world environment, is completely controlled. This means that
confounding variables are reduced to a minimum. Furthermore, the VE can be a
simulation of an existing environment, but it could also be a newly invented environment
which would eliminate familiarity as potential confounding variable as well. Another
advantage of VEs is the ability to use fMRI to study neural activation during navigation
and route-learning (which normally requires movement) (e.g. Maguire, Burgess and
O’Keefe, 1999).
External validity: Although VEs are designed to be as close to natural as possible,
several limitations can be pointed out. First of all, the field of view is limited to the size
of a monitor and therefore typically narrower than the field of view available in the real
world. Second, the screen will always have reduced resolution which makes a virtual
environment look different from a real environment. A third and most important
limitation of VE research is that moving through a PC-based virtual environment does
not require actual movement. Navigation is thus based on merely visual information in
the absence vestibular and proprioceptive information. For these reasons, one could
question whether findings in VEs could be generalized to real-world environments. Some
studies have shown that this form of generalization is possible. Ruddle, Payne and Jones
27
(1997) for instance, have demonstrated that spatial memory performance in VEs and in
real world environments are comparable. They found that people learn to navigate inside
VEs with accuracy similar to inside real buildings. Their study also demonstrated that
making VEs more realistic with everyday objects for landmarks as an alternative of using
cubes with abstract patterns, improved navigation performance. Furthermore, Munzer and
Stahl (2008) observed that an animated virtual walk instruction significantly improved
performance during the actual walk in a real building compared to route instructions in
the form of an allocentric map or egocentric sequences of pictures.
In contrast, Skorupka (2008) and Ruddle and Jones (2001) reported that the
navigation pattern in VEs differs from navigation patterns in real environments: in VEs,
as contrasted with real world environments, people tend to follow generally straight
paths. As a result, the time to reach a destination (an elevator) was longer in a virtual
building than in a real building (Skorupka, 2008). Furthermore, a study by Farrell,
Arnold, Pettifer, Adams, Graham and MacManamon (2003) reported that VE training did
not provide better route learning than studying a map. They also demonstrated that VE
training in combination with studying a map did not improve performance compared to
studying a map alone. This indicates that VEs may not transfer well to the real world.
As made obvious by the foregoing, spatial behaviour in VEs and real
environments is not necessarily equivalent. Therefore, to study spatial memory in a VE
may not be as accurate as in a real-world environment. This is possibly due to the
limitations described earlier. However, as technologies are developing, more naturalistic
VEs can be generated. Bulthoff, Campos and Meilinger (2008) describe VEs in which the
field of view can be larger and displays can have high resolutions. Furthermore,
sophisticated self-motion interfaces have been developed where participants can navigate
inside VEs through actual walking. Bulthoff et al. (2008) also notify that limited walking
is made possible by omni-directional treadmills. One major disadvantage of these
advanced VEs is that they are far more expensive than the use of PC-based VEs.
4.3. Spatial tasks in natural environments
When you measure spatial memory in everyday environments, two decisions must be
made: 1) which environment should be selected and 2) which task will measure the aspect
28
you want to measure. To explore different aspects of everyday spatial memory, a variety
of spatial tasks can be carried out in natural settings. Before we discuss the validity of
measuring in natural settings, we present an overview of different methods to measure
spatial memory in natural environments.
Pointing
When you point towards certain objects in space that is out of view, you have to first
determine your own position in the environment, subsequently the position of the object
in space, than you orient towards the object in space and finally you move your hand in
the appropriate direction. Lemay and Proteau have implemented several studies in which
they used manual pointing as a measure for effects of aging (2002, 2003), visual
background information (Lemay, Gagnon and Proteau, 2004), and movement duration
(2001). Among others, these studies show that pointing towards unseen targets can be
used to assess how target location can be specified in an egocentric frame of reference
that are encoded in either an egocentric or an allocentric frame of reference. Moreover,
pointing has also been used to assess configurational knowledge about the spatial layout
of the environment (De Goede, Berthoz, Zaoui and Postma, submitted; Rieser, Guth and
Hill, 1986). None of these studies however, were carried out in a natural environment: in
the Lemay and Proteau studies, participants were pointing towards a computer screen and
De Goede et al. used a virtual environment. We suggest that pointing towards target
locations could also be measured in the natural environment in order to measure e.g.
large-scale object-location memory from an egocentric perspective or how well metric
aspects of the environment are processed in an ecologically valid setting. Furthermore,
different natural settings may show how different contexts (i.e. different environments)
may help or impair pointing abilities. Pointing accuracy can be quantified by measuring
the absolute angular error in degrees (cf. Mou, McNamara, Valiquette and Rump, 2004).
On condition that a scaled map is available, the accuracy in angular degrees can be
assessed in every possible environment.
29
Way finding
Another method to measure spatial memory in real-world environments is to let people
navigate in actual buildings or cities. This method has been used in several studies in the
natural environment (e.g. Chang and Fotios, 2008; Munzer and Stahl, 2008; Van Asselen
et al., 2006). In the study by Van Asselen et al. (2006), incidental learning was compared
to intentional learning during a walk through a building. Chang and Fotios (2008)
explored way finding behaviour in unfamiliar buildings in order to investigate whether
buildings could be designed to improve way finding. Objective information can be
gathered during route learning or way finding in real environments: Van Asselen et al. for
example scored recalled landmarks in the correct position and order, number of correct
decisions on a map drawing task and during route reversal navigation, and finally had the
distance estimated in meters. Chang and Fotios also used decision points to analyze the
routes and looked at how often certain strategies were used (calculating the percentage
following a certain strategy on all decisions). These examples indicate that way finding
behaviour in real environment can be studied and quantitative data can be obtained.
Verbal route instructions
Another interesting issue in everyday spatial memory concerns how well humans can
verbally describe routes (e.g. from the post-office to the supermarket). It could be a
measure of allocentric spatial memory: how well do people know spatial relations
between landmarks (i.e. between the post-office and the supermarket, or between the
post-office and the church where you have to turn left)? Furthermore, it could be
observed how much details a large-scale cognitive map may encompass (in terms of
either landmarks or metric distances and configurations). In a study to further develop
human-robot communication, it is observed that a robot can transform human verbal
route instructions into a metrical route graph (Bauer and Buss, 2008). This demonstrates
that verbal route instructions can be transformed into quantitative data and utilized to
assess the accuracy of these instructions. We consider therefore that verbal route
instructions in the natural environment could give a proper representation of the cognitive
map that people generate and use of this map in everyday life.
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Locating oneself on a map
To locate yourself on a map you require the ability to orient yourself in the environment,
convert 3D spatial information into 2D from above view and estimate the spatial relations
between yourself and surrounding objects (e.g. buildings or roads). To explore how well
people can orient themselves in a familiar or unfamiliar environment, or to what extent
people can generate a ‘from above’ view of the environment one could have people
locating themselves or other objects on a map. For instance, Liben, Myers and Kastens
(2008) studied people’s abilities to mark their locations on a map and found that
performance varied widely across individuals. Performance on a specific spatial task (i.e.
a paper folding task assessing spatial visualization) predicted performance on the
mapping task. This method is a suitable measure to assess a person’s ability to convert
natural environmental large scale space into small scale 2D from above view. Again,
objective and quantitative data can be obtained which makes it a useful method to
compare different groups or spatial abilities in different situations.
Large-scale object locations
To measure the use of spatial memory in a relatively large-scale and static natural
environment, one could have people recall the locations of certain objects in an everyday
environment. Lutz, Means and Long (1994) carried out a study on a large parking lot.
They measured everyday object-location memory by letting people recall where they
parked their car. Several tasks were performed in this study: participants marked the
location on a map (measuring allocentric cognitive map abilities) and reported which
strategies they used for remembering the location (or for getting back to the car). A
similar experiment was carried out by Plukaard, Van Oers, Back and Postma
(unpublished), using an even larger parking lot and more participants. Along with
defining strategies used and marking the location of the car on a map, the distance
between a predetermined location and the location of the car was estimated (to test
coordinate coding of space), and a pointing task was performed (to test egocentric
abilities, participants were asked to point towards the location of the car). These studies
show that many different aspects of spatial memory can be assessed and that objectlocation memory in a large-scale everyday environment may involve many components
31
of spatial memory. The individual tasks to measure large-scale object location behaviour
can give quantitative results. By selecting the appropriate environment (in the latter
study: a parking lot in front of a shop) and by obtaining information about the familiarity
of the environment, current mood and other personal issues that may affect spatial
memory performance, confounding variables can be reduced to a minimum.
Construct validity: As many different tasks can be carried out in everyday settings and as
the use of spatial memory is measured in settings in which it is actually used, these tasks
are the best way to measure everyday spatial memory. Nevertheless, one should always
make sure that the appropriate task is chosen to measure a certain form of spatial
memory. That is, ‘pointing’ should be used to measure orienting, allocentric cognitive
map abilities and not to measure dynamic spatial memory abilities such as navigation.
Internal validity: One disadvantage of measuring in the real environment is the
increased probability of confounding variables that may lead to unreliable results. For
instance, specific sounds can be used (and are used in everyday life) as spatial cues: an
experimental session in which a church bell rings may lead to different results than a
session in the same environment in the absence of this sound. Therefore, the
experimenter should seek to minimize confounding variables such as specific sounds or
other external cues, familiarity of the environment (which should be similar to all
participants), and weather conditions (rain or fog can change the appearance of the
environment). However, complete elimination of confounding factors is almost
impossible in field research. Another problem with measuring in the real-world
environment is that it is difficult to repeat a study in a real environment as environments
change through time. This is also the advantage of measuring spatial memory in everyday
environments since spatial memory is normally applied in changeable settings. To find
similar results in repeated studies in a changing environment will therefore strengthen
spatial memory findings.
External validity: The major advantage of measuring in the real environment as an
alternative of measuring in laboratory settings is that you can measure the behaviour as it
most likely would be in everyday life. In laboratory settings, participants have less
freedom in how they apply spatial memory, they have less external cues that normally
32
help them to move around or recall spatial settings, and problems might be encountered
that do not occur in everyday life or the other way around. All tasks described above can
be used in different environmental settings such as familiar or unfamiliar, hectic or calm,
complex or simple and in emotionally disturbing (simulating emergency situations) or in
passive and unexciting settings. This will improve ecological validity of spatial memory
studies.
5. Conclusions and recommendations
The outline of this review consisted of evidence for different forms of spatial memory
and how these forms relate to different memory problems in everyday life, the everyday
problems were classified, different factors that may lead to everyday spatial memory
problems were described and finally different methods to assess everyday spatial memory
were presented.
Deficits in specific forms of spatial memory can be a result of age, gender,
neurological damage, perceptual impairments, stress or mood. These factors can therefore
lead to particular problems in everyday life, such as losing objects or getting lost
yourself. In Table 1, we present an outline of different everyday spatial memory
problems that can be divided into different groups of everyday problems and the related
forms of spatial memory and underlying factors. This table clarifies how forms of spatial
memory, underlying factors and specific everyday problems are interrelated. In chapter 2,
we created groups of spatial memory problems that correspond to the same divisions, that
is, if different problems are each large scale, long term and dynamic spatial memory
problems; they are assigned to one group. With these groups, one problem may predict
other spatial problems that are assigned to the same group. Table 1 confirms this
assumption where for example ‘taking a longer route than necessary’ and ‘giving other
people wrong route directions’ are assigned to the same group (dynamic-long term -large
scale). These two problems also involve mostly similar components of spatial memory
and similar groups of people may encounter these problems. Obviously, the content of
this table and also the content of these groups should be tested and confirmed by future
studies. One thing that leaps out in this table is that ‘age’ and ‘hippocampal damage’ are
factors that may cause all everyday spatial memory problems. Whether some problems
33
occur less frequently than others or which problems have greatest impact on everyday life
is not yet entirely clear. Again, future research should shed more light on this issue. Other
factors, such as mood and visual impairments may cause more specific problems in
everyday life.
More knowledge about everyday spatial memory problems and about whether these
problems fit into the groups and the table we have put forward, could perhaps contribute
to improved spatial memory performance in elderly, impaired, male or female, and
anxious people in different environments or during different situations. At present, the
groups and Table 1 are developed based on independent spatial memory studies that are
exceedingly dissimilar not just in the use of methods, settings and participants, but also in
their aims. We suggest that an inventory should be made about everyday spatial memory
problems for different groups of people. Surveys and questionnaires are suitable methods
to accumulate a large amount of information from a large number of people (as such,
including different groups of people) as long as the questions are detailed and simple.
This review has shown that multiple components (and likewise specific everyday
spatial memory problems) can be tested in natural settings using various methods. A
strong advantage of measuring spatial memory in everyday settings is that spatial
memory is measured as it is actually used in everyday life. However, a major and very
important disadvantage is that the experimental conditions are mostly uncontrolled which
leads to increased influence of confounding factors that might bring down the reliability
and validity of the results. Furthermore, to study route learning or navigating in many
different environments may not be very practical or attainable. These disadvantages of
measuring in real-world settings are in fact the advantages of VE studies. VEs are
completely controlled close-to-natural environments that can resemble every possible
real-world setting without restrictions. It is therefore easy to create either familiar or
unfamiliar environments. The only problem with VEs is that it is not completely clear to
what extent behaviour in VEs can be generalized to behaviour in the real world. Several
studies have revealed contradictory results about whether or not behaviour in VEs
transfers to behaviour in real environments. The main restrictions that may prevent
spatial memory performance in VEs to resemble spatial memory performance in the real
34
world are the small field of view and the inability to truly move while ‘walking’ around
in a VE. However, making VEs more realistic has already proven to increase the
generalizability of VE spatial memory performance. In addition, recent VE developments
have made actual walking in a 360 degrees surrounding VE possible. Based on these
findings and on the fact that a controlled experimental setting is essential to obtain
reliable results, we strongly support the use of VEs in future everyday spatial memory
research.
35
Everyday spatial memory problems
Underlying factors
Dynamic-short term-large scale
Prospective /
Retrospective
Retrospective
Static-short term-small scale
Retrospective
Age; HIPP damage; Monocular vision; Mood
OLM
Static-long term-small scale
Retrospective
Age; HIPP damage; Monocular vision; Mood
CM
Prospective
Age; Gender; HIPP/PFC damage; Mood
RL
Static-long or short term-small
to large scale
Dynamic-short term-large scale
Retrospective
Age; PFC/HIPP damage; Blindness; Low vision
Problems with estimating distances
between buildings
Taking a longer route than necessary
CM; ALL; COO
Static-long term-large scale
Age; Gender; HIPP damage; Blindness; Mood
RL; CM; ALL
Dynamic-long term-large scale
Prospective /
Retrospective
Prospective
Giving other people wrong route
directions
Forgetting the route you followed
earlier
Pointing into wrong directions
RL; CM; ALL;
EGO
RL
Dynamic-long term-large scale
Prospective
Age; PFC/HIPP damage; Blindness; Low Vision
Dynamic-short term-large scale
Retrospective
Age; PFC/HIPP damage; Low vision
OLM; CM; ALL;
EGO; COO
Static-short term-large scale
Prospective /
Retrospective
Age; HIPP damage; Monocular vision; Blindness;
Mood
Getting lost in a strange city
Forgetting where you left your keys in a
new room
Forgetting where you left your keys in a
familiar room
Being unable to read or to understand
a map
Forgetting how you got somewhere
Spatial memory
components *
RL; CM; EGO;
ALL
OLM
Group of everyday problems
Age; PFC/HIPP damage; Blindness;
Age; PFC/HIPP damage; Blindness; Low Vision
* RL = Route Learning; CM = Cognitive Map; EGO = Egocentric frame of reference; ALL = Allocentric frame of reference; OLM = Object Location Memory; COO =
Coordinate coding
Table 1: This table includes several spatial memory problems and shows which components of spatial memory may be involved, in which group that
particular problem would fit, whether the problem concerns pro- or retrospective spatial memory and which underlying factors may have
caused each problem.
36
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