change of plans:

Change of Plans:

Read Intro and Expt. 1 in article by Lee Brooks for Wed.

Read Beth Loftus for Monday Nov. 29th

Memory

Short-Term “Working” Memory

Overview of Memory

• Atkinson-Shiffrin Model

Sensory Signals

Sensory Memory

Short-Term Memory

Long-Term Memory

ATTENTION

REHEARSAL

RETRIEVAL

Short-Term Memory

• process by which we hold information “in mind”

Short-Term Memory

• process by which we hold information “in mind”

• example: temporarily remembering a phone number

Characteristics of STM

• Capacity? Duration?

• How could you measure these parameters?


• Limited Duration– Brown-Petersen Task:

• subject is given a trigram (e.g. C-F-W) to remember

• vocal rehearsal is prevented by counting backwards

• recall accuracy tested as a function of retention interval


• STM decays over seconds


• Limited Duration– Brown-Petersen Task Interpretation: rapid

loss of information in STM (over a period of seconds…much longer than sensory memory)


• Limited Capacity– How might you measure capacity?


• Limited Capacity– George Miller – Subject is given longer and longer lists of to-

be-remembered items (words, characters, digits)


• Limited Capacity– George Miller – Subject is given longer and longer lists of to-

be-remembered items (words, characters, digits)

– Result: Subjects are successful up to about 7 items


• Limited Capacity– What confound must be considered ?!


• Limited Capacity– What confound must be considered ?!– Recalling takes time !


• Limited Capacity– What confound must be considered ?!– Recalling takes time !– It seems that the “capacity” of STM (at least

measured in this way) depends on the rate of speech - faster speech leads to apparently larger capacity

– Some believe capacity is “2 - 3 seconds worth of speech”


• Limited Capacity– “chunking”: grouping items into

meaningful bundles increases STM capacity (in some sense)

– Example: 111 333 666 333 777 222

Forgetting from STM

• Why do we “forget” from STM?– Does the memory trace decay?

• not likely because with very small lists (like 1 item) retention is high for long intervals

Forgetting from STM

• Why do we “forget” from STM?– Does the memory trace decay?

• not likely because with very small lists (like 1 item) retention is high for long intervals

– Instead, it seems that information “piles up” and begins to interfere

Forgetting from STM

• Interference in STM is complex and specific

Forgetting from STM


• For example, severity of interference depends on meaning

Forgetting from STM


• For example, severity of interference depends on meaning– Subjects are given successive recall tasks with

list items from the same category (e.g. fruits)– final list is of either same or different category -

how is good is recall on this list?

Forgetting from STM

• Accuracy rebounds if category changes

Coding in STM

• How is information coded in STM?

Coding in STM

• How is information coded in STM?• Failures of STM give some clues:

Coding in STM


– Capacity decreases with increasing length of to-be-remembered words

Coding in STM



– phonological similarity effect - similar sounding items are harder to remember than different sounding items

Coding in STM



– phonological similarity effect - similar sounding items are harder to remember than different sounding items

• What does this suggest about coding in STM?

Coding in STM

• Information in STM can be coded in an “auditory” (or subvocal) way

• Try to sketch a model of STM with boxes and arrows

change of plans:

Documents

capacity of stm

stm capacity

failures of stm

stmlimited capacitychunking

information piles

list items

rapid loss of information

capacity decreases