Transcript weiten6_PPT07

Chapter 7
Human Memory
Human Memory: Basic Questions
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How does information get into memory?
How is information maintained in memory?
How is information pulled back out of memory?
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Fig 7.2 – Three key processes in memory. Memory depends on three sequential processes: encoding,
storage, and retrieval. Some theorists have drawn an analogy between these processes and elements of
information processing by computers, as depicted here. The analogies for encoding and retrieval work pretty
well, but the storage analogy is somewhat misleading. When information is stored on a hard drive, it remains
unchanged indefinitely and you can retrieve an exact copy. As you will learn in this chapter, memory storage is a
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much more dynamic process. Our memories change over time and are rough
reconstructions rather than exact copies of past events.
Encoding: Getting Information Into Memory
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The role of attention
 Focusing awareness
 Selective attention = selection of input
– Filtering: early or late?
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Fig 7.3 – Models of selective attention. Early-selection models propose that
input is filtered before meaning is processed. Late-selection models hold that
filtering occurs after the processing of meaning. There is evidence to support early,
late, and intermediate selection, suggesting that the location of the attentional filter
may not be fixed.
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Levels of Processing: Craik and Lockhart
(1972)
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Incoming information processed at different levels:
Deeper processing = longer lasting memory codes
Encoding levels:
– Structural = shallow
– Phonemic = intermediate
– Semantic = deep
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Fig 7.4 – Levels-of-processing theory. According to Craik and Lockhart (1972), structural,
phonemic, and semantic encoding—which can be elicited by questions such as those shown on
the right— involve progressively deeper levels of processing, which should result in more
durable memories.
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Fig 7.5 – Retention at three levels of processing. In accordance with levels-of-processing
theory, Craik and Tulving (1975) found that structural, phonemic, and semantic encoding led to
progressively better retention.
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Enriching Encoding: Improving Memory
Elaboration
= linking a stimulus to other
information at the time of encoding
–Thinking of examples
Visual
Imagery = creation of visual images to
represent words to be remembered
–Easier for concrete objects: Dual-coding theory
Self-Referent
Encoding
–Making information personally meaningful
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Storage: Maintaining Information in Memory
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Analogy: information storage in computers ~
information storage in human memory
Information-processing theories
– Subdivide memory into 3 different stores
• Sensory, Short-term, Long-term
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Fig 7.8 – The Atkinson and Shiffrin model of memory storage. Atkinson and Shiffrin
(1971) proposed that memory is made up of three information stores. Sensory memory can
hold information just long enough (a fraction of a second) for a small portion of it to be selected
for longer storage. Short-term memory has a limited capacity, and unless aided by rehearsal,
its storage duration is brief. Long-term memory can store an apparently unlimited amount of
information for indeterminate periods.
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Sensory Memory
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Brief preservation of information in original sensory
form
Auditory/Visual – approximately ¼ second
– George Sperling (1960)
• Classic experiment on visual sensory store
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Fig 7.9 – Sperling’s (1960) study of sensory memory. After the subjects had fixated on the
cross, the letters were flashed on the screen just long enough to create a visual afterimage.
High, medium, and low tones signaled which row of letters to report. Because subjects had to
rely on the afterimage to report the letters, Sperling was able to measure how
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and the signal to report.
Short Term Memory (STM)
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Limited capacity – magical number 7 plus or
minus 2
– Chunking – grouping familiar stimuli for storage as a single
unit
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Limited duration – about 20 seconds without
rehearsal
– Rehearsal – the process of repetitively verbalizing or
thinking about the information
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Fig 7.10 – Peterson and Peterson’s (1959) study of short-term memory. After a warning
light was flashed, the subjects were given three consonants to remember. The researchers
prevented rehearsal by giving the subjects a three-digit number at the same time and telling
them to count backward by three from that number until given the signal to recall the letters. By
varying the amount of time between stimulus presentation and recall, Peterson and Peterson
were able to measure how quickly information is lost from short-term
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memory.
Short-Term Memory as “Working Memory”
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STM not limited to phonemic encoding
Loss of information not only due to decay
Baddeley (1986) – 3 components of working memory
– Phonological rehearsal loop
– Visuospatial sketchpad
– Executive control system
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Fig 7.11 – Short-term
memory as working
memory. This diagram
depicts the revised model
of the short-term store
proposed by Alan
Baddeley (1986), who
views STM as a mental
scratchpad or temporary
workspace. According to
Baddeley, working
memory includes three
components: a
phonological rehearsal
loop, a visuospatial
sketchpad, and an
executive control system.
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Long-Term Memory: Unlimited Capacity
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Permanent storage?
– Flashbulb memories
– Recall through hypnosis
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Debate: are STM and LTM really different?
– Phonemic vs. Semantic encoding
– Decay vs. Interference based forgetting
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How is Knowledge Represented and
Organized in Memory?
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Clustering and Conceptual Hierarchies
 Schemas and Scripts
 Semantic Networks
 Connectionist Networks and PDP Models
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Retrieval: Getting Information Out of
Memory
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The tip-of-the-tongue phenomenon – a failure in
retrieval
– Retrieval cues
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Recalling an event
– Context cues
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Reconstructing memories
– Misinformation effect
• Source monitoring, reality monitoring
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Forgetting: When Memory Lapses
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Retention – the proportion of material retained
– Recall
– Recognition
– Relearning
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Ebbinghaus’s Forgetting Curve
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Fig 7.18 – Ebbinghaus’s forgetting curve for nonsense syllables. From his experiments
on himself, Ebbinghaus concluded that forgetting is extremely rapid immediately after the
original learning and then levels off. However, subsequent research has suggested that this
forgetting curve is unusually steep. (Data from Ebbinghaus, 1885)
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Fig 7.19 – Recognition versus recall in the measurement of retention. Luh (1922)
had subjects memorize lists of nonsense syllables and then measured their retention with
either a recognition test or a recall test at various intervals up to two days. As you can
see, the forgetting curve for the recall test was quite steep, whereas the recognition test
yielded much higher estimates of subjects’ retention.
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Why Do We Forget?
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Ineffective Encoding
Decay theory
Interference theory
– Proactive
– Retroactive
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Fig 7.21 – Retroactive and proactive interference. Retroactive interference occurs when
learning produces a “backward” effect, reducing recall of previously learned material. Proactive
interference occurs when learning produces a “forward” effect, reducing recall of subsequently
learned material. For example, if you were to prepare for an economics test and then study
psychology, the interference from the psychology study would be retroactive interference.
However, if you studied psychology first and then economics, the interference from the
psychology study would be proactive interference
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Fig 7.22 – Estimates of the prevalence of childhood physical and sexual abuse. In one of
the better efforts to estimate the prevalence of child abuse, MacMillan and her colleagues
(1997) questioned a random sample of almost 10,000 adults living in the province of Ontario,
Canada, about whether they had been abused during childhood. As you can see, males were
more likely to have experienced physical abuse and females were more likely to have suffered
sexual abuse. Moreover, the data support the assertion that millions of people have been
victimized by childhood sexual abuse, which is far from rare. (Based on
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data from MacMillan et al., 1997)
Retrieval Failure
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Encoding Specificity
Transfer-Appropriate Processing
Repression
– Authenticity of repressed memories?
– Memory illusions
– Controversy
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Fig 7.24 – The prevalence of false memories observed by Roediger and McDermott
(1995). The graph shown here summarizes the recognition test results in Study 1 conducted by
Roediger and McDermott (1995). Participants correctly identified words that had been on the
lists that they had studied 86% of the time and only misidentifed unrelated words that had not
been on the lists 2% of the time, indicating that they were paying careful attention to the task.
Nonetheless, they mistakenly reported that they “remembered” related target words that were
not on the lists 84% of the time—a remarkably high prevalence of false memories. (Data from
Roediger & McDermott, 1995)
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The Physiology of Memory
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Biochemistry
– Alteration in synaptic transmission
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Hormones modulating neurotransmitter systems
Protein synthesis
Neural circuitry
– Localized neural circuits
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Reusable pathways in the brain
Long-term potentiation
Anatomy
– Anterograde and Retrograde Amnesia
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Cerebral cortex, Prefrontal Cortex, Hippocampus,
Dentate gyrus, Amygdala, Cerebellum
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Fig 7.25 – The anatomy of memory. All the brain structures identified here have been
implicated in efforts to discover the anatomical structures involved in memory. Although its
exact contribution to memory remains the subject of considerable debate,
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the hippocampus is thought to play an especially central role in memory.
Fig 7.26 – Retrograde versus anterograde amnesia. In retrograde amnesia,
memory for events that occurred prior to the onset of amnesia is lost. In
anterograde amnesia, memory for events that occur subsequent to the onset of
amnesia suffers.
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Are There Multiple Memory Systems?
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Implicit vs. Explicit
 Declarative vs. Procedural
 Semantic vs. Episodic
 Prospective vs. Retrospective
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Fig 7.27 – Theories of independent memory systems. There is some evidence that different
types of information are stored in separate memory systems, which may have distinct
physiological bases. The diagram shown here, which blends the ideas of several theorists, is
an adaptation of Larry Squire’s (1987) scheme. Note that implicit and explicit memory are not
memory systems. They are observed behavioral phenomena that appear to be handled by
different hypothetical memory systems (the procedural and declarative
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memory systems), which cannot be observed directly.
Improving Everyday Memory
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Engage in adequate rehearsal
Distribute practice and minimize interference
Emphasize deep processing and transfer-appropriate
processing
Organize information
Use verbal mnemonics
Use visual mnemonics
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