Notes can be found as interactive webpage at

8: Memory Process

Three-Stage Model of Memory #

  • Three-stage modal model of memory; Atkinson-Shiffrin model:
    1. Sensory memory
    2. Working memory or short-term memory
    3. Long-term memory
  • Old model that’s not used today
    • Sensory memory is seen as a type of perception
    • Short term is similar to attention
  • Interesting to study to see how our model evolved and how memories are processed

Sensory memory #

  • Holds sensory information very briefly (1/2 to 4 secs)

    • If you stare at an image then close your eyes you can still see the image
    • Large capacity store
    • Sensory input is held very briefly in sensory memory to allow selection and processing of information
    • Now often considered to be a part of perception

    (a) was flashed, then (b), and people reported seeing (c) [Eriksen & Collins, 1967]

  • Two types of sensory memory:

    • Iconic memory (photographic memory): visual sensory memory – doesn’t go away after four seconds but functions like sensory
    • Echoic memory: auditory sensory memory

Eidetic imagery (photographic memory): #

  • Eidetic memory: Characterized by relatively long-lasting and detailed images of visual scenes that can sometimes be scanned and “looked at” as if they had real existence

    Examples of people with a photographic-like memory are rare. Eidetic imagery is the ability to remember an image in so much detail, clarity, and accuracy that it is as though the image were still being perceived. It is not perfect, as it is subject to distortions and additions (like episodic memory), and vocalization interferes with the memory

    • Eidetic imagery is relatively rare – only 5% or so of tested schoolchildren have it and proportion is much smaller in adults
    • It is not an especially useful form of mental activity.
      • Contrary to popular lore, memory experts don’t generally have eidetic imagery; their skill is in organizing material in memory, rather than in storing it in picture form.
  • Group of schoolchildren was shown a picture for 30 seconds. Picture was taken away, and children asked whether they could still see anything and, if so, to describe what they saw. Some children showed evidence of this kind of memory.

    • 10-year-old boy, looking at blank easel from which a picture of Alice in Wonderland had just been removed, is asked whether he sees something there (on the blank easel)
    • Participant (P): I see the tree, gray tree with three limbs. I see the cat with stripes around its tail.
    • Experimenter (E): Can you count those stripes?
    • Participant (P): I see the tree, gray tree with three limbs. I see the cat with stripes around its tail.
    • Experimenter (E): Can you count those stripes?
    • P: Yes (pause). There’s about 16.
    • E: You’re counting what? Black, white or both?
    • P: Both.
    • E: Tell me what else you see.
    • P: And I can see the flowers on the bottom. There’s about three stems but you can see two pairs of flowers. One on the right has green leaves, red flower on bottom with yellow on top. And I can see the girl with a green dress. She’s got blond hair and a red hair band and there are some leaves in the upper left-hand corner where the tree is. (Leask, Haber, & Haber, 1969)

Short-term memory (STM) / Working Memory #

  • Holds items that are actively being thought about
    • That is, intentionally rehearsing information
  • Has limited capacity
    • 7 +/- 2 items, e.g., letters, words, dots, though this number can vary by task
    • Number of words you can speak in 1.5 seconds (those who speak faster can recall more)
  • Also limited in time, but longer than sensory memory
    • Lasts 5 to 30 seconds
    • Information decays rapidly unless maintained in consciousness through rehearsal
  • Working memory (Baddeley) is now the preferred term because it emphasizes that this is an active, rather than a passive, process
    • Includes a phonological loop (associated with the left hemisphere) that briefly stores sounds, and a visuospatial sketchpad (associated with the right hemisphere) that stores visual and spatial information
      • Just recall left is associated with language and right is generally ‘wholistic’
      • Two visuospatial tasks will interfere with each other if performed simultaneously, as will two items in the phonological loop
      • However, people can perform a verbal task and a spatial task simultaneously
      • Aside: Feynman
  • Episodic buffer: another component of working memory that can hold and combine information from phonological loop, visuospatial sketchpad and long-term memory to form a story – important in time sequencing
    • E.x. if you’re trying to recall how someone reacted to a joke you made last night; you think about what you said / how you said it / how they reacted / etc.
  • Central executive: integrates information from phonological loop, visuospatial sketchpad, and episodic buffer
    • Similar to attention/sensory memory in Atkinson Shriffin model

Long-term memory (LTM) #

  1. Repository of all one’s knowledge
  2. Unlimited in the amount it can store
  3. No time limit

Serial position effect #

  • Evidence for short-term memory and long- term memory: serial position effect
  • Also called primacy-recency effect
  • Six lists test (first five are fruits, last is animals)
    • There is a tendency for people to remember best the items learned first (because of LTM) and the items learned last (because of STM)
    • Proactive interference (PI): words from previous lists interfere with your ability to learn new words of a similar nature (doing progressively worse on Lists 2-5)
    • Release from PI: items are different so no interference memory for these items should be good (doing well on list 6)
    • Retroactive interference: words from later list interfere with recall of a prior list (difficulty recalling items from list 1 at the end)

  • Experiment also shows that semantic similarity of items affects recall
    • VEGT is harder to recall than ANQR

  • Medical applications of serial position effect
    • Our memories of how painful an experience was tends to depend on the peak intensity and how much pain was felt at the end
      • Participants in experiment were asked to immerse one hand in painfully cold ice water for 60 secs, then other hand in same ice water for 60 secs followed by a slightly less painful 30 secs more (Finn, 2011)
        • When asked which trial they would prefer to repeat, most participants preferred the longer trial, with more net pain – but less pain at the end
    • Strategy of tapering off pain (though this means increasing net pain experienced) has been implemented in painful medical procedures like colonoscopies
  • Serial position can color our memory of pleasures too
    • In one experiment, participants, on receiving a fifth and last piece of chocolate, were told it was their “next” one
    • Others were told it was their “last” piece
    • The latter liked the chocolate better and also rated the whole experiment as being more enjoyable (O’Brien & Elsworth, 2012)
    • Possible applications to romantic relationships?

Types of long-term memory #

Explicit memory #

  • Explicit/declarative memory (with conscious recall): recall or recognition of information; can be verbally transmitted
    • Episodic memory: recall of personal facts (autobiographical)
    • Semantic memory: recall of general facts
  • Implicit/non-declarative memory (without conscious recall): memory that influences one’s behavior or thought but does not itself enter consciousness; cannot be verbally transmitted
    • e.x. you can’t teach someone how to ride a bike by explaining to them
    • Procedural memory: Recall of how to do things
    • Also includes conditioning effects – see Édouard Claparède’s experiment

Implicit Association Test #

  • implicit.harvard.edu
    • 80% of those who have ever taken the test end up having pro- white associations, including about 50% of African Americans
  • Does the IAT correlate with specific behaviors?
    • White college students who had more implicit negative stereotypes of Black people showed significantly more nonverbal signs of discomfort (e.g., standing further away, making less eye contact, stumbling over words more, smiling less) when interviewed by Black interviewers
    • People with a stronger pro-White bias on the IAT were also more likely to perceive anger and apparent threat in Black faces (Greenwald, Banaji, & Nosek, 2015; Hugenberg & Bodenhausen, 2003)
  • How can implicit stereotyping be reduced?
    • In case of black-white implicit stereotyping, thinking about admired out-group member (Tiger Woods) and disliked in-group member (Jeffrey Dahmer) can reduce implicit IAT bias for up to 24 hours
      • Imagining counter-stereotypic women (e.g., strong women) similarly reduces implicit stereotyping
    • Students enrolled in a prejudice and conflict seminar taught by a black professor show a reduction in implicit biases after participation in course, as compared with controls (Devine, P.G., 2001) (Rudman, Ashmore, & Gary, 2001)
      • Long-term impact
  • The power of implicit attitudes: Newlyweds’ implicit and explicit attitudes toward their new spouses were measured
    • Explicit measure: spouses asked to report extent to which they would describe their marriage using 15 pairs of opposing adjectives (e.g., “good” vs. “bad,” “satisfied vs. “dissatisfied”)
    • Implicit measure: version of IAT that required spouse to indicate as quickly as possible the valence of positively and negative valenced words after being exposed to 300-ms primes of photos of their partner and various control individuals
    • Marital satisfaction was tracked over 4 year period
    • Implicit attitudes were a better predictor of future marital happiness than their explicit attitudes (McNulty, Olson, Meltzer et al., 2013)

Neurobiology of memory processing #

Where in the brain is long-term memory stored? #

  • Karl Lashley (1950)
    • Rats learn maze
    • Lesion cortex (of different location each time)
    • Test memory
      • Still performed better than brand new rat
      • Thus, Memories do not reside in single, specific spots

Long-term potentiation (LTP) #

  • Long-term potentiation (LTP): mechanism through which learning occurs in brain
    • A long-term increase in the excitability of a neuron to a particular synaptic input caused by repeated high-frequency activity of that input
      • Stimulating a particular neural circuit will increase the sensitivity of neurons in that circuit, increasing the probability that they will fire again
    • Process involves binding of glutamate to NMDA receptor
      • More glutamate can be bound
      • More synapses can be formed
      • Make NMDA receptor more sensitive to binding
  • What LTP means psychologically: Both positive and negative thoughts tend to be self-reinforcing

    The more it snows (Tiddely pom),
    The more it goes (Tiddely pom),
    The more it goes (Tiddely pom),
    On snowing. And nobody knows (Tiddely pom),
    How cold my toes (Tiddely pom),
    How cold my toes (Tiddely pom),
    Are growing.
    – The House at Pooh Corner

    “Passing mental states become lasting neural traits” – Rick Hanson

The Hippocampus and Frontal Lobes #

  • Two structures that play particularly important roles in the processing and storing of new explicit memories are
    • Frontal lobes: recalling information and holding it in working memory
    • Hippocampus: “save” button for explicit memories
      • Used to believe that this is were memories were stored
      • We now understand the hippocampus acts as a ’loading dock’ where the brain temporarily holds to-be-remembered information
      • Items then migrate for storage elsewhere in process called memory consolidation
  • Example:
    • Removing a rat’s hippocampus 3 hours after it learns the location of some tasty new food prevents long-term memory formation
    • Removal 48 hours later does not (Tse, Langston, Kakeyama et al., 2007)
  • After a training experience, the greater one’s heart rate efficiency and hippocampus activity during sleep, the better the next day’s memory will be (Peigneux, Laureys, Fuchs et al., 2004; Whitehurst, Cellini, McDevitt et al., 2016)

Memory disorders: Evidence for Separate Memory Systems #

  • Dissociation: when brain damage affects two behaviors very differently, this suggests that the two behaviors are produced by different processes
    • Clive Wearing, an English musician, suffered damage to his hippocampus as result of encephalitis
      • If you walk out of the room, then come back 10 minutes late, he won’t remember you
      • But, he can still conduct a choir and play the piano and harpsichord beautifully
      • Due to damage to the hippocampus
      • Ala Memento

Explicit Memories: Hippocampus #

  • The hippocampus is central to the formation of explicit memories
    • People with full temporal lobe amnesia (damage to the hippocampus and surrounding areas) cannot form new explicit memories though they can form new implicit memories
    • They often have normal IQs and can carry on a normal conversation but cannot remember anything that happened more than a few minutes previously

  • The posterior hippocampus contains place cells, neurons involved in spatial navigation
    • Volume of posterior hippocampus is positively correlated with amount of time spent as a taxi driver
    • Follow-up study
      • London cabbies have to pass centuries old test, “ The Knowledge,” to get their license
      • They spend 3-4 years memorizing 25,000 streets
      • Voxel-based morphometry (VBM) was used to assess hippocampal volume before and after learning
      • Cabbies who passed the test showed significant growth in their posterior hippocampus, whereas controls did not (Maguire, Gadian, Johnsrude et al., 2000) (Woollett and Maguire, 2011)

Implicit memories #

  • Two structures that play important roles in the formation of implicit memories are…

Cerebellum: involved in learning of procedural memories for skills

  • Makes sense, implicit is mostly procedural memories

Basal ganglia: deep brain structure important in motor sequencing

  • Parkinson’s disease involves degeneration of parts of the basal ganglia
  • e.x. you want to get out of a chair but don’t know how
  • Cases of organic amnesia have provided evidence for the distinction between different memory systems (e.g., implicit and explicit)

Summary #

ACT-R: Hybrid Cognitive Architecture #

Controversies in Cognitive Science #

To what extent is the mind modular, that is, organized in special information-processing modules?


  • ACT-R: One of the most famous cogsci models: about how memory/information is stored and organized
  • “Adaptive control of thought – rational”
  • Cognitive architecture with modular organization that was developed by John R. Anderson in 1976
  • It is hybrid in sense that it incorporates both symbolic (e.x. static rules) and subsymbolic (i.e. neural networks) information processing
  • ACT-R buffer
    • Workspace: what you’re paying attention to
    • Serves to integrate outer and inner, between modules on different layers
    • Acts like control system: Theres a feedback loop where you send a command/signal and then get information back which you use to adjust subsequent commands
  • Perceptual-motor layer
    • Perceptual module in turn consists of a visual module, audition module, etc.
    • Motor module consists of speech module, manual module, etc.
    • E.x you can decide to move in a certain direction (motor movements, perceptual – you choose what to look at)

  • Cognitive layer
    • Declarative memory is organized in “chunks”
    • Procedural memory is encoded as production rules: actions for the system to perform, e.g., retrieve a chunk from memory, send a command to the motor module to perform an action
      • Production rules can be nested within each other, so that output of a given production rule will trigger firing of another production rule
  • All of the above modules are encoded in the form of physical symbols

What makes ACT-R a hybrid architecture is that the symbolic, modular architecture is run on a subsymbolic base

  • ACT-R is designed to operate serially, so that at any given moment, only one production rule can be active, but how does it select that one?

    • The pattern-matching module controls which production rule gains access to the buffer by working out which production rule has the highest utility at the moment of selection, as determined by
      • How likely the system is to achieve its current goal if the production rule is activated
      • The cost of activating the production rule

    • These calculations are subsymbolic and use an artificial neural networks approach
  • Subsymbolic equations are also used to model how accessible information is in declarative memory

    • The basic units of declarative memory are chunks, but each chunk is associated with a particular activation level, which is determined by
      • How useful the chunk has been in the past
      • How relevant the chunk is to the current situation and context

  • The general information processing that takes place in the buffers is symbolic
  • In contrast, the calculations that determine whether or not a particular item of knowledge ends up in a buffer are subsymbolic
Performance MechanismsLearning Mechanisms
SymbolicSub-SymbolicSymbolicSub-Symbolic
Declarative ChunksKnowledge (usually facts) that can be directly verbalizedRelative activation of the declaraitve chunks affects retrievalAdding new declarative chunks to the setChanging activations of declarative chunks and changing strength of links between chunks
Production RulesKnoledge for taking particular actions in particular situationsRelative utility of production rules affecting choiceAdding new production rules to the setChanging utility of production rules

Types of Memory Disorders #

  • Anterograde amnesia: inability to form lasting memories for new experiences
  • Retrograde amnesia: inability to remember events that occurred before the onset of condition

Organic amnesia: physical cause #

  • Brain injury through accident or stroke
  • Korsakoff’s amnesia (Wernicke-Korsakoff syndrome): amnesia caused by brain damage resulting from thiamine deficiency, usually as a result of chronic alcoholism
    • Not the alcohol, but lack of thiamine (nutritionally deficient)
    • Patient staggers, develops abnormal eye movements, becomes confused, and experiences severe loss of memory for recent and relatively long-term events
    • Patients tend to make things up (confabulate) rather than admit they can’t remember

      N.B.: In most cases of trauma-induced organic amnesia, there is spontaneous recovery after matter of minutes or hours

    • Tends to affect women (despite most alcoholics being men) since they have less of an enzyme to metabolize the alcohol

Psychogenic (“hysterical”) amnesia: psychological cause #

  • Dissociative identity disorder (multiple personality disorder): disorder in which a person exhibits two or more distinct and alternating personalities
  • Dissociative amnesia: inability to recall important personal information, usually precipitated by a traumatic experience
    • Hypnosis may be used to help recover memories
  • Dissociative fugue: disorder in which person has sudden, unexpected episode of travel from home during which he can’t remember some or all of his past life
    • Study found that incidence of this rises sharply whenever popular film depicting this subject is released

Alzheimer’s disease #

  • Organic
  • Disease occurring in latter part of life that is characterized by deterioration of memory, reasoning, and language abilities
  • Common form of neurocognitive disorder (deterioration of intellectual abilities; another common cause is vascular dementia)
    • Occurs in 7% of population above age of 65 and up to 40% of people older than 80 years
  • Associated with loss of neurons in cortical and sub-cortical regions: ventricles may be enlarged – patients might end up losing as much of 50% of their brain mass
    • Produces severe degeneration of large parts of the brain: can eventually destroy most of the hippocampus and cortical gray matter
  • Sometimes gets confused with dementia, parkinson’s, or other disorders
  • Deficiencies of acetylcholine: failure to show eyeblink conditioning

  • Brains of patients contain many amyloid plaques, which contain a core of misfolded b-amyloid protein surrounded by degenerating axons and dendrites, and neurofibrillary tangles, dying neurons that contain twisted filaments of tau protein

Causes #

  • Genetic component – in only ~10% of cases
    • People with down syndrome tend to develop it
  • Higher risk of disease in those who have previously suffered a stroke or head trauma
    • Wear a helmet!
  • Conditions associated with cardiovascular disease, e.g., obesity, diabetes, high blood pressure, high cholesterol, smoking, and lack of exercise, increase risk
  • Associated with low levels of vitamin D and certain B vitamins
    • Eat veggies for vitamins (prevents strokes too)
  • Exposure to lead and toxic substances, such as air pollutants, may increase risk
  • Article published in Lancet in 2017 noted that hearing loss is now known to be the largest modifiable risk factor for developing dementia, exceeding that of smoking, high blood pressure, lack of exercise, and social isolation
  • Research indicates that use of anticholinergics (in many drugs) is associated with reduced brain volume and lower levels of glucose metabolism, particularly in the hippocampus
    • Anticholinergics include Tylenol PM, Benadryl, Claritin, Dimetapp, Paxil, and Xanax
      • Researchers concluded that these drugs could trigger or worsen Alzheimer’s (Gray, Anderson, Dublin et al., 2015)
    • Those on anticholinergics also showed poorer performance on cognitive tests
  • Also, studies have found that older people with tooth and gum disease score lower on memory and cognition tests
    • Experts speculate that inflammation in diseased mouths migrates to the brain

Preventing #

  • Those who stay physically active and are non-obese have lower risk of developing disease
    • Heart health => brain health
  • Studies have found that people who keep their minds active tend to show less loss of intellectual functioning in general as they age
    • Study of nuns in convent (Snowdon, 1997) found that education and intellectual activity seem to protect against Alzheimer’s
    • Study also found that degree of sentence complexity and amount of positive affect expressed in writing samples when subjects were in their 20’s were negatively associated with incidence of disease and positively associated with longevity
      • There have been cases where autopsies showed presence of disease but no symptoms had been present
    • Use it so you don’t lose it!

Do Plaques and Tangles Really Cause Alzheimer’s? #

  • Claudia Kawas’ 90+ study on the “oldest old”
    • Team of medical experts were asked to examine years of medical records to determine if each of participants had Alzheimer’s
    • 40% of participants that they concluded had Alzheimer’s did not have any amyloid plaques or neurofibrillary tangles at death
    • On the other hand, about half of participants who died without symptoms of dementia had plaques and tangles

  • Conclusion?
    • Maybe plaques and tangles have nothing to do Alzheimer’s (unlikely)
    • There may be multiple factors (e.g., lack of physical exercise, lack of cognitive stimulation, history of head trauma, etc.) that contribute to the development of Alzheimer’s…
      • Whether people develop the disease may depend on the number of “hits” they take from these various factors

Q&A #

  • Q: Which regions of the brain are thicker in successful agers than in regular agers? Those regulating cognition or emotion?
  • A: Those regulating emotions, e.g., the midcingulate cortex and anterior insula.
  • Q: What type of activities will increase your chances of remaining sharp into old age?
  • A: Those that require hard work and cause you to feel somewhat tired, stymied, frustrated, e.g., grappling with a math problem or pushing yourself to your physical limits. (From research by Dr. Lisa Feldman Barrett)
  • Q: What factor most lowered people’s risk of getting dementia?
  • A: Tiny strokes called microinfarcts
    • Some participants had hundreds or thousands of them
  • Q: What caused symptoms of dementia in those who died without plaques and tangles?
  • A: Not vitamins, not alcohol, not caffeine, not exercise…. but high blood pressure!
    • High blood pressure => less likely
    • Note though that this study focused exclusively on people over 90 years of age – results may be different for younger people

Hyperthymesia #

  • Hyperthymesia of Superior Autobiographical Memory: Rare condition in which one has virtually perfect memory from about age of 10
    • Larry Cahill and James McGaugh constructed extensive memory tests to assess extent of each memory of each of six subjects
      • What was the date of the fall of the Berlin wall?
      • How many times did it rain in 1986?
    • Associated with enlarged hippocampus and caudate nucleus: standard deviation of 7 or 8 – equivalent to a 10-foot tall person, as opposed to 5’9"
    • Often associated with OCD type behavior; only 1 of 6 are married