Memory (1)

Atkinson & Shiffrin (1968) Model of Memory

Visual Sensory Store• It appears that our visual system is able to hold a great

deal of information but that if we do not attend to this information it will be rapidly lost.

• Sperling (1960)– Presented array consisting of three rows of four letters– Subjects were cued to report part of display

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Demo at:http://www.dualtask.org/

Visual Sensory Memory

• Vary the delay of cue in partial report

• After one second, performance reached asymptote

Delay of cue (in seconds)

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Iconic Memory

• Sperling’s experiments indicate the existence of a brief visual sensory memory – known as iconic memory or iconic store

• Information decays rapidly unless attention is transfers items to short-term memory

• Analogous auditory store: echoic store

Atkinson & Shiffrin (1968) Model of Memory

Short-term memory (STM) is a limited capacity store for information -- place to rehearse new information from sensory buffers Items need to be rehearsed in short-term memory before entering long-term memory (LTM)

Probability of encoding in LTM directly related to time in STM

a memory test...

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Serial Position Effects

• In free recall, more items are recalled from start of list (primacy effect) and end of the list (recency effect)

• Distractor task (e.g. counting) after last item removes recency effect

distractor task

nodistractor

task

Serial Position Effects

• Explanation from Atkinson and Shiffrin (1968) model:

– Early items can be rehearsed more often more likely to be transferred to long-term memory

– Last items of list are still in short-term memory (with no distractor task) they can be read out easily from short-term memory

Forgetting over time in short-term memory.

Peterson and Peterson (1959)

Baddeley’s working memory system.

Baddeley proposed replacing unitary short-term store with working memory model with multiple components:

• Phonological loop• Visuo-spatial sketchpad• Central executive (ignore the episodic buffer)

Baddeley and Hitch (1974)Baddeley (1986)

Phonological Loop(a.k.a. articulatory loop)

• Stores a limited number of sounds – number of words is limited by pronunciation time, not number of items

• Experiment:

• Word length effect – mean number of words recalled in order (list 1 4.2 words; list 2 2.8 words)

• Phonological loop stores 1.5 - 2 seconds worth of words

LIST 1:BurmaGreeceTibet

IcelandMaltaLaos

LIST 2:Switzerland Nicaragua

Afghanistan Venezuela Philippines

Madagascar

Two routes to phonological loop

• Articulatory control process converts visually presented words into a speech code

• Articulatory suppression (e.g. saying “the” all the time) disrupts phonological loop

• Prediction: – Word length effect depends on phonological loop– With articulatory suppression, visually

presented items should not display word length effect

Visualpresentation

Auditorypresentation

Speech code

Phonological loop

Articulatory control process

Immediate word recall as a function of modality of presentation (visual vs. auditory), presence vs. absence of articulatory suppression, and word length.

Baddeley et al. (1975).

Working memory and Language Differences

• Different languages have different #syllables per digit

• Therefore, recall for numbers should be different across languages

• E.g. memory for English number sequences is better than Spanish or Arabic sequences

(Naveh-Benjamin & Ayres, 1986)

Evaluation of the Evidence for the Phonological Loop

• Accounts for phonological similarity and the word-length effect

• Support from neuroimaging studies• Baddeley, Gathercole, and Papagno (1998)

– Its function may be to learn new words

Encoding & Retrieval Effects

Levels of Processing(Craik & Lockhart, 1972)

Levels of processing effect:Deeper levels of processing (e.g., emphasizing meaning)leads to better recall.

Encoding Specificity Principle

• Recollection performance depends upon the interaction between the properties of the encoded event and the properties of the retrieval information

Context Change

• Information learned in a particular context is better recalled if recall takes place in the same context

• Similarly, information learned in a particular context may be difficult to recall in a dramatically different context

Godden & Baddeley (1975, 1980)

Memory experiment with deep-sea divers– Deep-sea divers learned words either on land or underwater– They then performed a recall or recognition test on land or

underwater

Mood-dependent Memory

Kenealy (1997).

• Easier to remember happy memories in a happy state and sad memories in a sad state.

• Subjects study positive or negative words in normal state. Test in positive or negative induced states.

mood primes certain memory contents

State-dependent recall

• Does physical state matter?• Eich et al. (1975): study while smoking normal or

marijuana cigarette. Test words under same or different physical condition

Forgetting

Forgetting Functions• Ebbinghaus (1885/1913): Forgetting over time as

indexed by reduced savings.

Most forgetting functions show:

Negative acceleration

Rate of change gets smaller and smaller with delay

Power law of forgetting

Forgetting

Why do we forget?

Some possibilities:• Memory has disappeared

decay theory

• Memory is still there but we can’t retrieve it

repression

inhibition theory

interference theory

What is Repression?

• “Something happens that is so shocking that the mind grabs hold of the memory and pushes it underground, into some inaccessible corner of the unconscious.”

- Loftus (1993)

• Some self-help book (“Courage to Heal”) relate repressed memories to sexual abuse

Recovered memory vs. False Memory

• How do we know whether repressed memories are accurate?

• In some cases, traumatic information is misremembered or simply “made up”– Loftus has been involved in many cases– Points out problems of

• hypnosis• suggestive questioning• dream interpretations

Elizabeth Loftus

False Memory in the Lab• Deese, Roediger, McDermott paradigm

• Study the following words

• Recall test ....

• Recognition memory test

Use ratings 1) sure new 2) probably new 3) probably old 4) sure old

• TEST:

BEDRESTAWAKETIREDDREAMWAKESNOOZEBLANKETDOZESLUMBERSNORENAPPEACEYAWNDROWSY

SNORERESTCOFFEESLEEP

Results• Critical lure (“sleep”) are words not presented but similar

to studied words. These words are often falsely recalled (sleep: 61% of Ss.)

• Recognition memory results

proportion of items classified with confidence levels:

confidence rating 4 3 2 1

studied items .75 .11 .09 .05not studied

unrelated .00 .02 .18 .80critical lure .58 .26 .08 .08

(e.g. “REST”)

(e.g. “COFFEE”)

(e.g. “SLEEP”)

Subjects reporting recovered memories are more vulnerable to false memories

False recognition of words not presented in four groups of women with lists containing eight associates.

Clancy et al. (2000)

Proactive and retroactive interference

Inhibitory mechanisms in Forgetting

• Cued recall as a function of the number of times the cues had been presented before for recall (respond condition) or for suppression (suppress condition).

Anderson and Green (2001)