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CHAPTER 7
Memory
OUTLINE
I.
THE NATURE OF MEMORY
A. Basic Memory Processes
The process of putting information into memory is called encoding. Acoustic encoding
represents information as sequences of sounds. Visual encoding represents information in
the form of images. Semantic encoding represents the meaning of information. Holding
information in memory over time is called storage. Pulling information out of memory and
into consciousness after it has been stored is called retrieval.
B.
Types of Memory
There are at least three basic types of memory, each of which is named for the type of
information it handles. Any memory of a specific event that happened while you were
present is an episodic memory. Semantic memory contains generalized knowledge of the
world that does not involve memory of a specific event. Procedural memory (skill memory)
represents knowledge of how to perform physical tasks.
C.
Explicit and Implicit Memory
Explicit memory is the process of deliberately trying to remember something; implicit
memory is the unintentional influence of prior experiences. Explicit memory processes are
much more negatively affected by the passing of time than are implicit memory processes.
D.
Focus on Research Methods: Measuring Explicit vs. Implicit Memory
To document the difference between explicit and implicit memory, participants studied a
word list and were tested on it an hour later and a week later. For the explicit memory test,
participants picked which words on a new list had been on their study list. For the implicit
memory test, they solved word fragment problems. Explicit memory decreased between the
two tests, but implicit memory hardly changed. This research showed that time differentially
affects explicit and implicit memory.
E.
Models of Memory
Currently, there are four models of memory that attempt to explain what and how well items
such as processes, episodes, and general information are remembered.
1.
2.
3.
Information Processing. The information-processing model states that there are three
stages of mental processing required before information can be permanently stored in
memory: sensory, short-term, and long-term memory.
Levels of Processing. The levels-of-processing model suggests that what and how well
we remember are a function of how deeply information is processed or rehearsed and
encoded when first experienced. Maintenance rehearsal is simply repeating an item
over and over. Elaborative rehearsal is building associations or linkages between new
and old information. Elaborative rehearsal requires a deeper level of processing; hence
these memories are stronger than those encoded with maintenance rehearsal.
Transfer-Appropriate Processing. The transfer-appropriate processing model suggests
that the most important memory determinant is how well the encoding process matches
what is retrieved.
4.
II.
Parallel Distributed Processing (PDP). Parallel distributed processing (PDP) models
suggest that new facts change our knowledge base by altering interconnected networks,
facts, and associations. These networks allow us to quickly and efficiently draw
inferences and generalizations about new and old information.
5. Multiple Memory Systems. The multiple memory systems approach suggests that the
brain contains several separate memory systems, each of which resides in a different
area and serves a different purpose.
STORING NEW MEMORIES
A. Sensory Memory
Sensory memory holds information from all the senses in sensory registers for a fraction of a
second. Selective attention, which focuses mental resources on only part of the stimulus
field, controls which information in the sensory registers is actually perceived and
transferred to short-term and working memory.
B.
Short-Term Memory and Working Memory
Short-term memory (STM) receives the information that was perceived and selectively
attended to in sensory memory or retrieved from long-term memory. Short-term memory
stores information for a very limited amount of time. Working memory allows us to
mentally work with information held in short-term memory, making short-term memory a
component of working memory.
1.
C.
D.
Encoding in STM. Across cultures, people tend to use acoustic codes to encode
information into short-term memory. Visual codes tend to decay faster than acoustic
codes.
2. Storage Capacity of STM. The immediate memory span is the number of items you can
recall perfectly after one presentation of a stimulus. It is usually seven plus or minus
two chunks of information.
3. The Power of Chunking. Short-term memory can be noticeably improved by creating
bigger and bigger chunks of information. Efficient chunking requires the interaction of
short- and long-term memory.
4. Duration of STM. Brown-Peterson procedure research results indicate that, unless
rehearsed, material stays in short-term memory for about eighteen seconds.
Long-Term Memory
1. Encoding in LTM. Encoding information into long-term memory (LTM) is the result of
a deep level of conscious processing and usually involves some form of semantic
coding. Visual codes are also used to encode long-term memories. The dual coding
theory states that information is remembered better if both semantic and visual codes
are used.
2. Storage Capacity of LTM. Most theorists believe that there is no limit to the amount of
information that can be stored in long-term memory. However, long-term memories
are likely to be distorted. Flashbulb memories, for example, seem to be detailed
recollections but can be inaccurate.
Distinguishing Between Short-Term and Long-Term Memory
Psychologists disagree about the differences between short-term and long-term memory.
Some believe that short-term and long-term memory are the same; what is referred to as
short-term memory is the part of long-term memory that is being used at a particular
moment in time.
1.
Experiments on Recall. Serial position curves show a tendency to recall both the first
and last parts of a list (primacy and recency effects) when memory is immediately
tested. If participants are distracted just prior to being asked to recall a list, the primacy
effect remains, but the recency effect disappears. This suggests that the last words were
stored in short-term memory, which quickly decays.
III. RETRIEVING MEMORIES
Retrieval is the ability to bring a memory into consciousness.
A.
Retrieval Cues and Encoding Specificity
Retrieval cues help retrieve information from long-term memory. According to the encoding
specificity principle, these cues are more efficient when they reflect the meaning of the
originally encoded information.
B.
Context and State Dependence
When people remember more material while in a physical location that is similar to the one
where the material was originally learned, it is called context dependence. In state
dependence, people remember better when their psychological state is the same as it was
when the information was encoded. In the mood congruency effect, information processing
is facilitated if a person’s emotional state is similar in tone to the information being
processed.
C.
Retrieval from Semantic Memory
1. Semantic Networks. One theory states that semantic memories are represented in a
dense network of hierarchical associations. Strong associations and/or those at the top
of the hierarchy are quickly retrieved. Network theory suggests that information is
retrieved through a spreading activation process; for example, thinking about concept
A spreads neural activity to all other features, attributes, and concepts associated with
concept A.
2. Retrieving Incomplete Knowledge. In a phenomenon called incomplete knowledge (as
in the tip-of-the-tongue phenomenon), we often retrieve features and attributes of a
concept but cannot access the entire concept. For example, we may feel that we would
recognize the answer to a trivia question if we were presented several options (feelingof-knowing experience).
Constructing Memories
People construct memories from their existing knowledge to fill in gaps in new information
that is being encoded.
D.
1.
E.
Relating Semantic and Episodic Memory: PDP Models. PDP models allow us to
increase our general knowledge of the world by accessing a network of facts and
associations. A note of caution: PDP models can facilitate spontaneous generalizations
of networks that are based on limited or biased information.
2. Schemas. According to PDP models, the generalized knowledge contained in schemas
provides the basis for making inferences about incoming information during the
encoding stage.
Linkages: Memory, Perception, and Eyewitness Testimony
Witnesses can accurately report what they have seen or heard but can be biased by the
manner in which questions are asked and relevant occurrences are discussed. Jurors may rely
too heavily on how witnesses present evidence, such as reporting a great deal of detail or
appearing very confident of what they are reporting.
IV. FORGETTING
A. How Do We Forget?
Hermann Ebbinghaus’s contributions to psychology included demonstration of the method
of savings and the shape of the forgetting curve. The forgetting curve, which depicts how
much and when people forget, stays relatively constant regardless of the type of information
learned.
B.
Why Do We Forget? The Roles of Decay and Interference
Decay, the gradual erosion of a memory, is the most common culprit for short-term memory
loss. Interference causes forgetting by interrupting the encoding or retrieval process through
the presence of other information. In short-term memory, new information displaces old
information because of the limited number of spaces available. However, in long-term
memory, space is not the issue; rather, as the number of stored memories increases, it
becomes more and more difficult to “find” one particular memory among the huge number
of memories. Interference, the main cause of forgetting in long-term memory, can be
retroactive or proactive.
C.
Thinking Critically: Can Traumatic Memories Be Repressed, Then Recovered?
What am I being asked to believe or accept?
Some people claim that subconscious processes such as repression could keep a person from
recalling a memory.
What evidence is available to support the assertion?
Research supports that mental activity can occur outside of awareness, that implicit
memories can influence people, and that the use of retrieval cues can allow people to access
buried memories. In addition, people may be motivated to forget especially unpleasant
events.
Are there alternative ways of interpreting the evidence?
Even vivid retrieved memories may have been constructed. A person might be led by books
or therapists to construct false memories.
What additional evidence would help to evaluate the alternatives?
If we knew how frequently people repress traumatic memories, it would be easier to evaluate
such reports. Knowledge of the process leading to repressed memories and a method for
distinguishing between genuine memories and constructed memories would also help
evaluate the alternatives.
What conclusions are most reasonable?
Although people do forget unpleasant events and remember them later, they also may distort
their memories. For now, people should neither uncritically accept nor reject a report of a
recovered memory, but should investigate the evidence for and against the claim.
V.
BIOLOGICAL BASES OF MEMORY
Brain cells change as memories are formed and stored.
A.
The Biochemistry of Memory
Two types of synaptic changes occur during memory formation: New synapses are formed,
and communication at existing synapses is improved. Neurotransmitters, such as glutamate
and acetylcholine, are involved in memory processes.
B.
Brain Structures and Memory
The hippocampus and the thalamus are important in the formation of new memories.
Memories are stored in many different areas of the cortex. However, no single brain
structure or neurotransmitter is exclusively involved in memory formation or storage.
1.
The Impact of Brain Damage. Hippocampal brain damage often results in anterograde
amnesia, a loss of memory of events occurring after the injury. Patients cannot transfer
new experiences from short-term memory to long-term memory. Retrograde amnesia is
the loss of memory of events prior to an injury. Although many injury patients regain
most of their memories, few can recall the events just prior to the injury. As a result of
the injury, the short-term memories of what happened were never transferred to longterm memory. Memory deficits in several medical conditions support the theory that
short-term memory and long-term memory are distinct storage systems.
2. Multiple Storage Areas. Long-term memories are stored in and around the cortex, but
not all in one place. Multiple sensory and motor systems are involved in memory, and
some evidence suggests the sensory and motor areas involved in formation of a
memory are activated at retrieval.
VI. APPLICATIONS OF MEMORY RESEARCH
A. Improving Your Memory
1. Mnemonics. Mnemonics are strategies for remembering information. The method of
loci associates well-known locations with information to be remembered.
2. Guidelines for More Effective Studying. Create a context, such as an outline, for
organizing information. Elaborate the new information and associate it with related
knowledge you already possess. Remember that distributed practice is more effective
than massed practice.
3. Reading a Textbook. Make sure you understand what you are reading before you go
on. Use the PQ4R method of preview, question, read, reflect, recite, and review.
4. Lecture Notes. Focus on creating a framework for facts (outline) and expressing major
ideas in relatively few words. Finally, work to see and understand the relationship
between facts and concepts. Review your notes as soon as possible after a lecture and
fill in the gaps.
B. Design for Memory
The scientific study of memory has influenced the design of electronic and mechanical
devices that play important roles in our lives.