PSY 368 Human Memory

PSY 368 Human Memory

Short Term Memory cont.Working Memory

Reminders

• Exam 1 one week from today (Feb 15)• Review sheet posted, linked to syllabus• Experiment 1 report also due 1 week from

today

Experiment 1 assignment

• Experiment 1 - Primacy and Recency Effects in Short-term Memory (modified from Neath & Surprenant book pg. 61)• Download from BB assignments page. Find 3 friends willing to participate• Report (Due Wednesday Feb. 15): The results for all subjects will be

reported in class. Your assignment is to write a 2-3 page report that includes the following:• brief description of the purpose and design of the experiment, including independent

and dependent variables• brief description of the participants, materials, and procedure of the study, written in

your own words• description of results and line graph of mean percentage recall by serial position • discussion of conclusions that can be made from the results. Include answers to these

questions:• How long does short-term memory appear to last?• How important is attention to retrieval from short-term memory?• What kinds of everyday tasks in life use short-term memory?

Structural Model

• Memory composed of storage structures that hold memories for a period of time • Sensory memory• Short-term memory (STM)• Long-term memory (LTM)

Structural Model• Brief review from last time

• Capacity:• Can hold 7 + or - 2 “chunks”(capacity)• Chunking increases capacity of STM

• Encoding: • Info mostly stored in auditory form (but

some visual, some semantic)• Duration:

• Brown/Peterson task: decay, gone by 15-20 sec

• Keppel & Underwood; Waugh and Norman suggest interference as better explanation

• Retrieval:

• Two groups of subjects given 3 trials following the Brown-Peterson task (letters) - Memory performance declined with each trial• Control group given a 4th trial using letters• Experimental group switched to remembering digits

Wickens, Born, & Allen (1963)

STM Duration

• Changing the nature of the items to be remembered reverses the decline in performance due to proactive interference- release from proactive interference• Proactive interference: already learned info interferes with new information

• Retroactive interference: new information interferes with old information (more on this in chapter 6)

7

• Experimental group, but not control group, performed perfectly; they were released from proactive interference

Wickens, Born, & Allen (1963)

STM Duration

• Changing the nature of the items to be remembered reverses the decline in performance due to proactive interference- release from proactive interference

8

• Proactive interference occurring as a result of semantic coding in STM

• 5 groups of subjects given 3 trials of lists of 3 words each all from the same category where all list contained names of fruit

Wickens (1970, 1972, 1976)

• Group 1 – names of fruit

• Group 2 – vegetable names

• Group 3 – flower names

• Group 4 - names of meats

• Group 5 – names of different professions

• Then all groups given a 4 trial where all list contained names of fruit

STM Duration

Wickens (1970, 1972, 1976)

STM Duration

1st trial all

groups about 90% correct

• Results:

2nd trial more words in same category

all groups about 50%

3rd trial words still in same category

all groups 35–45 %

4th trial , shift to fruit category

professions 80%, meat 50%, flowers 47%, vegetables 40% and fruit 32%

Wickens (1970, 1972, 1976)

STM Duration

• Results:

• Conclusion: • Interference rather than decay causes the drop in

performance• Information was coded using semantic information

causing groups to confuse current list with previous lists

STM Duration• Duration:

• STM is short store of about 15-20 s• Loss of information initially thought to

be due to decay. • More recent work suggests

interference more likely reason

STM RetrievalHow do we get information out of STM?•Retrieval from STM appears to operate by searching STM contents one at a time (serial search)

• Sternberg (1966)• Serial position recall curves: primacy and recency

STM Retrieval• study short list of 1 to 6 items followed by test probe

- must decide if probe item was in list, measured time to make Y/N response

• Two important variables were involved• The number of letters in each list• The location of the letter in the memory probe – in the

beginning, middle, or end

Sternberg (1966)

• Serial processing• Operations being done one after

another• It should take longer to retrieve four

digits than to retrieve two digits• Exhaustive serial processing – the

participant always checks the test digit against all digits in the set, even if a match were found partway through the list

• Self-terminating serial processing – the participant would check the test digit against only those digits needed to make a response

STM Retrieval

• Parallel processing• Simultaneous

handling of multiple operations

• Response times should be the same, regardless of the size of the set of items, because all comparisons would be done at once

Sternberg (1966)

• Results• Response times increased

linearly with set size but were the same regardless of serial position

• It indicates that serial exhaustive model seems to be right

• Subjects take longer to respond by probe (by 40 ms) when an additional item is added to the list

• Same results for probes that were in the list and probes that were not

STM Retrieval

• Conclusion: people search all items in STM when asked to retrieve an item (happens very fast)

• Automatic process - fast and efficient, done for every item – doesn’t stop once a match is found

Sternberg (1966)

Serial Position Curve: Free recall

STM Retrieval• Primacy: • better recall for

items in the beginning of the list than those in the middle

• Recency:• better recall for

items at the end of the list than those in the middle

• Models of STM propose that • Primacy is due to more rehearsal for items at beginning of

list - LTM• Recency due to immediate dumping of items from STM

Free recall Curve

From Murdock (1962)

• Primacy: • better recall for




STM Retrieval

• Models of STM propose that • Primacy is due to more rehearsal for items at beginning of list -

LTM• Recency due to immediate dumping of items from STM• Recency is stronger effect than primacy in free recall

Free recall Curve vs. serial recall curves

• Primacy: • better recall for




• due to retrieval from STM

From Klien et al. (2005)

STM Retrieval

Modal Model of STM: Summary

• Duration: STM is short store of about 20 s • Capacity:

• Can hold 7 + or - 2 “chunks”(capacity)• Chunking increases capacity of STM

• Encoding: Info mostly stored in auditory form

• Retrieval: Modal models suggest recency effects mostly due to STM retrieval

Problems with the Modal Models

• When distractor task is done after every list item preventing items from staying in STM, recency effect still occurs

• Primacy effects have also been shown to disappear when rehearsal is prevented

• Long-term recency effects• Baddeley and Hitch (1977) Rugby Study

• Question: “Which teams have you played this past season?”

• Results:• Recency effect: Recent games were recalled best.• The total number of games played, not the amount of

time gone by, best predicted forgetting.

More Recent Models• Current models focus more on processing (than

structures) and that include STM in some form (storage and manipulation of information)• There are multiple models that have been called “Working

Memory,” designed to account for similar sets of data

VisionTouch

Hearing

STM

Rehearsal

WM

LTM• Models of WM assume:• That STM is a

storage unit and that WM = processes involved in completing a task

• That WM requires consciousness - includes info we are currently attending to

Working Memory• Today we will talk about 3 theories of

WM• Baddeley’s model of WM (Baddeley,

1986, 2000)• Cowan’s activation model (Cowan,

1988, 1995)• Nairne’s feature model (Nairne, 1988,

2001)

Baddeley’s Model• Currently the most influential model

• Baddeley and Hitch (1974)• Components of the model:

• Central executive controls the focus of attention

• Three subsystems under its control• Visuospatial sketchpad• Phonological loop• Episodic buffer

Baddeley’s Model

ArticulatoryControl

Visual scribe

Baddeley’s Model

ArticulatoryControl

Visual scribe

Central Executive• Thought to be an attentional controller, with

two main modes of operation (Norman & Shallice, 1986):• A semi-automatic conflict-resolution system, based

on existing habits and requiring little attention.• The supervisory attentional system (SAS), based

on an attentionally limited executive.

• Major Functions:• Direct attention to the task at hand• Divide attention between two or more tasks

Baddeley’s Model

ArticulatoryControl

Visual scribe

Visuo-spatial Sketchpad

• Stores and manipulates visual and spatial information of images

• May be separate parts for visual info (color) and spatial info (orientation, location)

• Info enters through perception or internally generated visual images

• Controls tasks like mental rotation and geographical search of a visual or mental image

location

orientationcolor

Visuo-spatial Sketchpad

Baddeley (1992) • found that subjects’ memory for chess patterns

was more disrupted by a visual distractor task than an auditory oneShepard and Feng (1972)

• Imagine folding the shapes below to create a solid, with the shaded area as the base. Will the arrows meet head on?

•found that the time it takes to answer the question depends on the number of folds required

Baddeley’s Model

ArticulatoryControl

Visual scribe

Episodic Buffer• Back-up storage - allows for recall when

other systems are engaged with other tasks• A storage system with a capacity of around 4 chunks of

information in a multidimensional code.• Multiple dimensions permit links between the subsystems, as

well as with LTM & perception.• Information is retrieved through conscious awareness –

consciousness pulls info together.• Allows for the binding of previously unrelated concepts --

disrupting the executive does not impair binding, so it may be automatic/passive.

• Newest component of the model, not much research yet

Baddeley’s Model

ArticulatoryControl

Visual scribe

Phonological Loop• Two parts: Phonological Store (PS) and

Articulatory Control Process (ACP)• PS - stores auditory info for 1-2 s and then it starts to

decay• ACP - recodes visual info into auditory code for storage

and controls rehearsal• 4 Main Effects in Serial Recall Task to account

for• Phonological similarity effect• Articulatory suppression effect• Irrelevant speech effect• Word length effect

Phonological Loop• Demos

Listen to list, recall words in order

RhinocerosZincGorillaTuberculosisMeaslesCalciumUraniumCarbonHippopotamusMumps


PlanetMusicianLandPropertyTrumpetHouseStarCometOrchestraMoon

Listen to list, recall words in order, while I read the words say ‘the’ aloud

BlockBrickStickBlueChewTrickPrickClueClickBlimp

Read list, recall words in order, while I read the words say ‘the’ aloud Gold

CodeBoldHoldToldColdModeSlowedHopeGoad

Recall


BronzeBookMagazineBikeCopperDressCopierSodaShoeRock

Phonological Loop• Demos


RhinocerosZincGorillaTuberculosisMeaslesCalciumUraniumCarbonHippopotamusMumps


PlanetMusicianLandPropertyTrumpetHouseStarCometOrchestraMoon


BlockBrickStickBlueChewTrickPrickClueClickBlimp

Read list, recall words in order, while I read the words say ‘the’ aloud

GoldCodeBoldHoldToldColdModeSlowedHopeGoad


BronzeBookMagazineBikeCopperDressCopierSodaShoeRock

Phonological Loop

• Memory worse for items that sound alike than those that look alike or have similar meanings

• Visual items are recoded to auditory for storage and rehearsal by ACP

• List 1 (Easy to remember/dissimilar phonology and semantics): • PIT, DAY, COW, PEN, HOT

• List 2 (Only slightly harder than List #1/similar semantics) :• HUGE, WIDE, BIG, LONG,

TALL• List 3 (Much harder than List

#1/similar phonology) :• CAT, MAP, MAN, CAP, MAD• What happens if you prevent the recoding of

visual information into auditory information?

• Works for both auditory presentation and visual presentation of the letters.

• Phonological Similarity Effect

Phonological Loop• Articulatory Suppression Effect

• Engaging in an auditory task after study removes phonological similarity effect for visual items• Procedure: Say “the” aloud over and over

• No re-coding of visual info by ACP• Phonological info gets in directly, doesn’t need re-coding

Auditory presentation: PGTCD (similar sounding) harder to recall than RHXKW (different sounding)Visual presentation: PGTCD (similar sounding) recalled equally as RHXKW (different sounding)

Phonological Loop• Irrelevant Speech Effect

• Background speech presented during study decreases memory for visual items

• Irrelevant speech interferes with recoding of visual info to auditory

• Visual info weak in WM • Something stored in the visuospatial sketchpad, but this

system not as efficient as the phonological loop

Phonological Loop• Word-length Effect

Results• Recall decreases as the

length of time it takes to say a word increases.

• Rehearsal takes longer for longer words - can’t rehearse as many times

Baddeley, Thomson, and Buchanan (1975)

• Retrieval from PS also takes longer due to auditory coding of items

• Reading rate correlated with memory ability• Digit span depends on language - how long it takes to

say numbers

• Potential Problems with the model• Some of the supportive results can’t be

replicated (e.g., irrelevant speech effect)• Model can’t explain all results:

• why word-length effect is larger for visual than auditory items

• why it differs based on serial list position• Model is not precise in explanation of effects

Baddeley’s Model

Cowan’s Activation Model

• Cowan (1999)• WM = info that is

currently highly activated from STM or LTM

• Focus of attention• Emphasizes attention’s

role in activation• Activation of info when

attention is oriented to it• Activation will decay to

cause loss of info from WM

STMWM


• Central Executive • Focuses attention and

other control processes• Capacity of about 4 chunks• Duration of 20s without

reactivation

• STM• activated items that are

just outside of attention - passive store• Things within attentional

focus are available to consciousness

STMWM

• Potential problems with the model• Only general descriptions so specific

predictions are hard to make• Activation is not operationally defined very

well - when is something is “activated”?• What causes decay? Passage of time isn’t

causal


Nairne’s Feature Model• Items represented in WM as individual

features (e.g., color, length, etc.)• Features indicate

• presentation info (e.g., font, size, gender of voice, etc.) • meaning info (e.g., what the item means, category, etc.)

• Features represented by -1 or +1 when studied (yes or no for a feature, 0 if no info for feature)

• Interference: Later items with same features overwrite feature info for previous items

Nairne’s Feature Model Bold Lower Upper BlueSCHOOL +1 -1 +1 -1fish +1 +1 -1 -1• “fish” presented after “SCHOOL”

- features in common can be overwritten - SCHOOL can become 0, -1, +1, 0- interference

During retrieval, item features are compared with items in memory - lost features can be updated and restored

Nairne’s Feature Model• Quantitative model - numerical

predictions are possible - can simulate data to generate predictions for studies• Simulations show that model can predict:

1) Recency effect2) Suffix effect3) Phonological similarity effect4) Word length effect

• Criticisms of the model• Jones and Macken (1995) showed that

irrelevant speech similarity had no effect• Model is complex - lack of parsimony

Nairne’s Feature Model

Summary of WM(1) Focus on processing (vs. storage)(2) Three main modern models

- Baddeley model - Central executive controls VS, PL, EB

- Cowan activation model - WM = attention focus, STM = activated

- Nairne feature model (quatitative)- Items coded as features with overwriting

interference

Documents

PSY 368 Human Memory