Download Memory

• The study of learning emphasises
acquisition process while the study of
memory emphasise on retention process.
• Memory is studied in terms of mental
processes involved in storing & retrieving
information.
Memory
• Human Memory is a system for storing and
retrieving information which is acquired
through our senses.
• It consists not of one but of many systems
which range in
a) Storage duration from fractions of a second
up to a lifetime and in
b) Storage capacity from tiny buffer stores to
the long-term memory system.
Memory
Memory
• Memory is our cognitive systems for
storing and retrieving information.
• We can form memories of
information, events, emotions, &
sensations.
• It is not a perfect system.
Theories
Theory of General Memory Functions
• Three distinct processes
1. Encoding Process: Transformation of a
physical stimulus into a form that human
memory accepts.
2. Storage: Retention of information that is
encoded.
3. Retrieval: Recovering information from
storage.
Information-Processing Theory
(Richard C. Atkinson & Richard M. Shiffrin, 1968)
Sensory Input
Sensory Memory
0.25 sec.-2 sec.
Some materials are
rehearsed & kept
in STM.
Short Term Memory
20-30 sec.
Retrieval
Some information is not
transferred to STM.
It is forgotten.
Some materials are not
transferred to LTM.
They are forgotten.
Rehearsal
Long Term Memory
Factors like decay &
interference may lead to
Forgetting from LTM.
Information Processing Model
• Right kind of information processing is more
important than intentional goal of learning.
• “Who am I?” - autobiographical memory:
Record of the experiences of a lifetime that go
together to create myself as a person.
• “What do I know?” - semantic memory:
• “How do I learn?”
• General information about the world
• Best method of efficient retrieval depends on how
material is stored.
Level of Processing Theory
(Craik & Lockhart, 1972) (Craik & Tulving, 1975)
Incoming Information
Depth of processing
Level 1: Perception
Level 2: Structural
Level
Level 3: Semantic
Level
Amount of elaboration
Neural Network Perspective
• Parallel distributed processing
• Collections of modules process
information in different ways
simultaneously
• Activation & spreading
• Memory is making or strengthening
interconnections
between
these
modules
A Model of Memory
Environmental Input
Sensory Register
Visual
Auditory
Haptic
Short-Term Memory
Working Memory
Control Processes:
Rehearsal
Coding
Decision
Retrieval Strategies
Long-Term Memory
Response Output
Sensory Memory
• Visual, hearing, smell, taste, touch
• The storage of sensory information
provides a microcosm of the memory
system as a whole.
Sensory Memory
• It begins with the systems of iconic and echoic
memory that store visual and auditory
information over a matter of milliseconds, as
part of the processes involved in perception.
• Both of these appear to have characteristics
that allow the initial stimulus to be prolonged,
probably so as to ensure that adequate later
processing is possible.
Sensory Memory
• VISUAL MEMORY
–
–
–
–
Iconic memory
Short-term visual memory
Flashbulb memory
Long-term visual memory
• AUDITORY MEMORY
– Echoic memory
– Short-term auditory memory
– Long-term auditory memory
Sensory
Memory
Sensory
Memory:
Visual
Iconic Memory
Echoic Memory
• Holds
information • Holds
information
for up to 1-2
for up to about 4-5
seconds.
seconds.
• 11-16 items can be
hold.
Sensory Memory: Auditory
ECHOIC MEMORY
• Persistence of audition
• Capable of storing sequences of at
least ~250 milliseconds and
possibly more
• Masking sound
Short Term Memory
• Information hold for 20-30 seconds after
which it is displaced by incoming information.
• Information encoded in STM is acoustic in
nature (Speech, Sounds, Visual Images &
Words).
• It is semantic in nature.
Meaningful words may be stored easily as
compared to nonsense syllables.
Short Term Memory
• Serial-Position Effect:
• Primacy Effect: Better recall of items at the
beginning of the list.
• Recency Effect: Items encountered most recently are
remembered well.
• STM can hold 5-9 chunks of information.
• Several items of information can be combined into one
chunk.
• About 7 chunks can be retained.
• About 40 items can be combined into 7 chunks & can be
held in STM.
Reason behind Primacy Effect
• Primacy effect remains during delayed
recall because the first items get time to
be put into LTM during the presentation
of the list.
Visual Memory
ICONIC MEMORY
•
•
•
•
•
FLASHBULB MEMORY
Holds information for • Phenomenon
of
vivid
up to 1-2 seconds.
memories of important
events
Visual persistence
• Not necessarily accurate:
~ 100 milliseconds
what we typically recall in
Short-time visual trace such situations is not what
‘icon’
we experience but what we
Features such as color, abstract
from
that
shape and direction can experience (i.e. Eyewitness
be stored
testimony, Recognition of
faces).
Brightness-masking
•
• Pattern-masking
Auditory Memory
SHORT-TERM AUDITORY MEMORY
• There is evidence for two short-term auditory
storesa) one operating over a timescale of 150-350
milliseconds, and
b) the other one lasting somewhere between 2
and 20 seconds.
• Modality effect: Advantage to spoken terms
• Recency effect: Enhanced recall of the most
recently presented items
Auditory Memory
LONG-TERM AUDITORY MEMORY
• Memory for language: Stored in terms of
meaning than sound.
• Memory for music: Both contour and pitch
interval information are retained.
• Memory for voices: Voice recognition of a
familiar person is reasonably good, but is poor
for a stranger.
Rehearsal in STM
(The process of keeping items of information in the
center of attention)
Maintenance Rehearsal
Elaborative Rehearsal
• Repetition
of • Giving the material
organization & meaning
information over &
as it is being rehearsed.
over again.
• Just going over & over • It uses strategies of
giving meaning &
again
does
not
organizing materials so
necessarily
succeed
that it can fit in with the
transferring
the
existing
organized
information into LTM.
LTM.
Short Term Memory
(Working Memory)
• 7+2 Chunks of memory can be kept in mind at
a time and combined to make a decision.
• The size of the chunk varies greatly between
experts and novices.
• Experts can combine many memory units to a
whole (e.g. master chess players retain a series
of moves)
Model of Working Memory
Allen D. Baddeley’s Model (1986)
(Little consensus at present)
• Articulatory Loop
(Verbal rehearsal takes place here)
• Visio-spatial sketchpad
(Rehearsal of visually presented information)
• Central executive
• Control & decision making
• Reasoning & Language comprehension
• Transfer to LTM
• Recency effects
(Short term buffer)
• Articulatory processes
• Recycling items for immediate recall
• If imagery task is difficult
executive’s resources are drained
• Visual Imagery Tasks
• If imagery task is difficult
executive’s resources are drained
fMRI: Working Memory
Fig. 1
Location of Working Memory
Fig. 2
Organization in Short Term Memory
In STM Chunks are organized in hierarchy.
• 5.6
• 4.1
• 2.0
• .25
Long Term Memory
• Intended to store information over a long time.
• It has unlimited capacity.
• Tulving
(1972,
1983)
,a
Canadian
Psychologist, was the first to make distinction
between episodic & semantic memory.
Long Term Memory
Declarative Memory
Semantic Memory
Specific Memory
Procedural Memory
Episodic Memory
Autobiographical
Memory
Long Term Memory
Episodic memory
• Represents our memory of events and
experiences in a serial form.
• Records an individual’s past experiences &
episodes of one’s daily life.
Long Term Memory
Long Term Memory
Semantic Memory
• It is a structured record of facts, concepts and
skills that we have acquired.
• Abstract knowledge & meaning of words,
symbols, etc. are retained.
• It also contains ideas & rules for relating them.
Autobiographical Memory
• Memories about event and experiences of
our own lives.
• The factors that affect other forms or
memory also affect organization of
autobiographical memory.
• Infantile Amnesia:
Supposed inability to remember events
from the first 2-3 year of life.
Semantic Memory
• This memory system stores general
knowledge that is not associated with a
specific place and time of acquisition.
Organization of semantic memory
• Semantic networks
• Concepts
• Prototypes
• Exemplars
Episodic Memory
• It is the memory for factual information that we
acquire at a specific time.
• Episodic memory is more susceptible to forgetting
as compared to semantic memory.
• Organizations of information in LTM is subjective.
• Images of information are concrete & abstract.
• Concrete words are easier to learn than abstract
words.
Episodic Memory
• Tip-of-the-tongue phenomenon supports the fact that
information in LTM is organized.
• Search in LTM is not random.
Factors affecting episodic memory:
memory
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Amount and spacing of practice
Type of processing
Levels of processing view
Retrieval cues
Context-dependant memory
State-dependant retrieval
Encoding specificity principle
New Developments in MEMORY
•
Items can directly go into LTM (Anderson, 1995).
•
Studies on patients gave two more concepts1. Implicit memory
2. Explicit memory
•
Two more concepts1. Declarative memory
2. Procedural memory
New Developments in MEMORY
• Declarative memory is memory of ‘what’, of
facts & events.
• Procedural memory is memory of ‘how’, or
the procedure.
• Procedural memory is usually implicit.
• It is the knowledge of how to perform a task.
• Older people show problems of Prospective
Memory (Fail to remember what they were
going to do).
Procedural Memory
• Memory systems that contain
information that we cannot readily
express
• Procedural knowledge & skilled
behaviors
• Skill acquisition
• Automatic & controlled processing
Sensory
STM
Approximate
duration
Iconic: 1-2 sec.
Echoic: 4-5 sec.
Capacity
Relatively large. At Relatively small. About 7 Very large.
least
16
items. items or chunks.
Limit unknown.
Probably much more.
Transference
20-30 seconds.
LTM
Attention
& Rehearsal:
Items
recognition.
appropriately rehearsed
Items attended to & move to LTM.
recognized move to
STM.
Days, months, years or
life time.
-
Copy of input.
Sounds, visual images, Primarily
meaningful
words & sentences.
sentences, life events &
concepts, some images,
semantic & episodic
memory.
Decay of trace.
Information
loss (Reason)
Displacement of old Faulty
organization,
information by incoming inappropriate
retrieval
information.
strategy, interference.
Type of
information
stored
Memory: Complex Cognitive Task
• There are fundamental differences between complex
tasks and standard memory tasks.
• Working memory does not consist of a single
general capacity, rather it consists of several
subsystems for various types of tasks.
• Working memory in a specific skilled activity
increases as one aspect of acquired skill.
• With practice and acquisition of memory skills,
recall performance on a specific memory task can be
improved by 100 to 1000%.
Memory in Children
• The effects of memory distortion
and construction are more
pronounced in children
• Children are more likely to
commit errors in reality and source
monitoring
Reconstructive Memory
Bartlett (1932)
• A group of students were asked to read a story about North
American Indians ‘The War of the Ghosts’.
• The story was reproduced after passing through several
mouths.
• Almost all details related to American Indian culture were
omitted & other were rationalized.
• Each narrator added something to the story from his own
imagination.
• Many details of the story was leveled, making it simpler.
• Narrators sharpened some other facts in the story &
exaggerated those aspects which they liked.
• All these processes changed the story.
Reconstructive Memory: Indian Contribution
• Durganand Sinha has done work on rumors in Indian setting.
• J.P.Das & R. Kanungo’s study>Two group of students (Brahmins & Kayasthas) were given 4 lists of
adjectives.
>List 1 had adjectives that described Brahmins in favourable terms: nice,
good looking, clean, etc.
>List 2 had adjectives that described Brahmins in unfavourable terms:
rude, greedy, fat, etc.
>List 3 had adjectives that described Kayasthas in favourable terms.
>List 4 had adjectives that described Brahmins in unfavourable terms.
¾ Brahmin students remembered adjectives favourable to them, but not
favourable to the Kayasthas Similar was the case with the Kayasthas.
¾ Everyone remembered more unfavourable adjectives than favourable
one.
¾ It suggests that, in general, people prefer to remember bad rather than
good attributes.
Zeigarnik Effect (B. Zeigarnik)
• This Russian psychologist compared memory for
tasks that were successfully completed & those
which were not.
• In fact she interrupted the work & did not allow
them to finish it.
• Interrupted tasks were remembered more frequently
than those which were completed.
# This mismatches with our daily experience.
Zeigarnik Effect: Indian Contribution
• Dutta & Kanungo gave a new interpretation to
Zeigarnik effect.
• The intensity of emotion aroused by the completed
or the interrupted task is the critical factor.
• Any activity that gives rise to strong emotion, be it
pleasant or unpleasant, is remembered better than
ordinary everyday action.
Memory Construction
• Recall of events that did not take place.
• Memory implantation
• These are not necessarily deliberate
• Suggestibility
• Source monitoring
• Illusion of out group homogeneity
Memory Distortion
• The change in the content of recall (memory) as a
result of internal or external factors.
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Cognitive biases
Suggestive questioning
Factors affecting distortion
Schemas
Motivation
Source monitoring
Reality monitoring
Methods for Studying Memory
• Free recall & recognition
• Sentence verification
• Priming
• Neuroimaging
Forgetting
• One characteristic of human memory is
that humans forget.
• Forgetting is a very useful attribute of the
human memory system.
• Forgetting happens if learned messages
haven’t been transfered to the long-term
memory.
• With hypnosis it is possible to retrieve
things that have been forgotten.
Forgetting
• During the process of forgetting important
features are filtered out and preserved, while
irrelevant or predictable detail is either
destroyed, or stored in such a way that it is not
readily accessible in its original form.
• One obvious benefit of forgetting is the way in
which it softens emotional pain or grief ”Time
heals all wounds” - but it also represents a
distortion of our recollection of the past.
Forgetting
• Forgetting
is
the
loss,
decay,
inaccessibility of information in LTM
• Interference
• Retroactive: Newly learnt information prevents
retrieval of previously stored ones.
• Proactive
• Retrieval inhibition
Repressed Memories
• Elimination of threatening or extremely
painful memories from consciousness
• Very controversial
• Methods of eliciting false memories
Effect of Mood on Memory
• Mood can serve as an internal
retrieval cues
• Mood-dependent memory
• Mood congruence effects
Towards Better Memory
• Overlearning (leads to automatisation)
• Mnemonics (Rhymes & jingles)
• Method of loci
• Number-peg technique
Memory Disorders
Amnesia
• Retrograde: Memory loss for things learnt
prior to the event initiating amnesia.
• Anterograde: Disruption of memory for
experiences after the onset of amnesia.
Alzheimer’s disease
• Gradual deterioration of memory functions
• It appears that chemical and neurotransmitters
may be involved
Memory Location in the Brain:
Hippocampus
• Transfers information from
memory to long term memory
working
• It helps the brain form memories by
stimulating it to form new synapses. Neurons
in the adult brain do not reproduce, they
simply form new synapses.
Memory Location in the Brain:
Hippocampus
• It appears that stimulation through the
hippocampus causes new synapses to form &
strengthen the synapses that already exist. This
process is called long-term potentiation, LTP.
• This is the primary means by which learning,
& consequently memory, takes place.
Memory Location in the Brain
• Frontal
lobes:
Working
memory,
lobes
encoding and retrieval of information
from long term memory
• Temporal lobes:
lobes Semantic memory
Memory Location in the Brain
• Some memories may be localized in certain specific areas of
the brain.
• Learning through classical conditioning is apparently stored
in the cerebellum (McCormick et al., 1982).
• However, there is also evidence that in many cases
memories are not stored in any single part of the brain.
• A single memory can be stored in numerous parts of the
brain, so that removal of any one part can diminish but not
erase the whole memory (Lashley, 1950) .
Memory Location in the Brain
• Once these new connections have been formed &
long-term potentiation has taken place, the
hippocampus is no longer necessary for the
particular memory- the memory & all its
connections to other information have become an
integral part of the brain’s structure & will persist
even if hippocampus is totally destroyed.
(Zola-Morgan & Squire, 1990; Squire & ZolaMorgan, 1991)
Summary of Memory Function
Fig. 3
References
1
www.nimh.nih.gov
2
www.nimh.nih.gov
3
Markowitsch, H.J. (1998). Cognitive Neuroscience of
Memory. Neurocase, 4, 429-435.