SHORT TERM MEMORY

5 ways we measure memory

assess memory without requiring conscious awareness of the remembered information.

conscious behavioural methods

tasks where participants actively recall or recognize information to study memory

unconscious behavioural methods

assess memory without requiring conscious awareness of the remembered information.

priming, habits, conditioning

Psychophysiological methods

measure bodily responses related to memory

GSR/HR

Electrophysiological methods

record electrical activity in the body or brain to study

EEG, ECG, EMG, MEG

Hemodynamic methods:

measure blood flow and oxygen in the brain involved in memory

PET, SPECT, fMRI

ATKINSON AND SHIFFRIN (1968) MULTI STORE MODEL OF MEMORY

(DRAW IT)

sensory store

Collects sensory information from the environment

Contains a store for each of our 5 senses (modality specific)

ionic memory

visual sensory memory

echoic memory

auditory sensory memory

Sperling (1960) METHOD

Participants saw a grid of digits and letters for 50 ms.

either asked to write down all items or were told they would hear a tone immediately after the exposure and they should recall one row (top, middle.

bottom)

Sperling (1960) RESULTS

When asked to report the whole thing their recall was poorer = five items recalled (42%)

when asked to give one row only = three items recalled (75%).

What does Sperling tell us about iconic storage?

Participants were able to report most of the letters from the requested row, but only if the removal of the array and presentation of the prompt was ~1 s or less

suggests that information in iconic storage decays in less than a second.

Treisman (1964) METHOD

presented participants with an auditory message to one ear and asked to repeat the message back aloud while ignoring a second message being presented to the other ear.

Treisman (1964) RESULTS

If the second, ignored, message was actually identical to the first but started at a different time, participants only noticed they were the same if they started within 2 seconds of each other.

shows that unattended sounds remain in echoic memory for about 2 seconds before decay

William James

Atkinson & Shiffrin's distinction between short-term and long-term stores was influenced by William James, who distinguished between the "psychological present" and the "psychological past"

short term store

According to Atkinson & Shiffrin, the short-term store contains information currently held "in mind", and is of limited capacity.

Jacobs (1887) METHOD

participants saw increasingly long lists of numbers or letters and had to recall them in the right order.

Jacobs (1887) RESULTS

Mean span for digits is 9.3

Mean span for letters is 7.3

Miller (1956)

investigated the capacity of STM by asking subjects to recall digit strings.

Typically, participants could recall strings correctly up to 7 ± 2 digits.

This result held for other stimuli like letters, and even for words

Chunking (Miller)

increase your digit span by organizing items into smaller, more manageable units

E.G. 020 8647 2380 is easier to recall than 02086472380

Cowan (2001)

conducted a meta-analysis and found that the capacity of short term memory is about 4 chunks

rehearsal

Information can be retained in short-term memory by REHEARSING it (either out loud or sub-vocally).

According to Atkinson & Shiffrin, the longer an item is held in STM, the greater likelihood of LT storage.

Rundus (1971) METHOD

ppts shown 20 words and asked them to rehearse the list out loud.

Rundus (1971) RESULTS

When asked to recall the words, the more frequently a word had been rehearsed, the more likely it was to be recalled

exception was the last few words in the list, which always had a high likelihood of recall irrespective of the amount of rehearsal.

Recency effect

the last few items in a list are often much better remembered than items from the middle of the list.

Peterson & Peterson (1959) METHOD

Tested 24 students in eight trials where they had to remember a consonant syllable (E.G. YCG)

also given a 3-digit number. The student counted backwards from this number

On each trial they were told to stop after diff periods of time: 3. 6, 9, 12, 15 or 18 seconds

Why did ppts have to count backwards?

to prevent any mental rehearsal of the consonant syllable (which would increase the duration of STM memory for the syllable)

Peterson & Peterson (1959) RESULTS

On average recall was about 80%, after 18 seconds it was about 3%.

suggests that STM duration may be about 18 seconds, unless we repeat the formation over and over

Waugh & Norman (1965)

manipulated the speed with which digits that were to be remembered were presented to participants and found that recall was (more or less) unaffected

suggests STM forgetting is due to interference from exposure to additional information, rather than the passage of time.

Glanzer & Cunitz (1966)

showed that the recency effect could be eliminated if participants counted backwards before recall

Counting backwards prevents participants from focusing on the last items

primacy effect

Earlier items in a list also tend to be better remembered than those in the middle

What is the link between LTM and the primacy effect?

Atkinson & Shiffrin proposed that the earlier items are recalled from LTM

Consistent with this, Glanzer & Cunitz found the primacy effect was unaffected by counting backwards after list presentation.

How can we prove that LTM and STM are separate?

Studies of patients with brain lesions

Where did patient HM have brain damage?

suffered medial temporal damage

Scoville & Milner (1957)

HM had impaired long-term memory but normal digit span.

preserved recency effect but a very reduced primacy effect

Where did Patient KF have brain damage?

suffered parieto-occipital lobe damage

Shallice & Warrington (1970)

Patient KF had intact long-term memory but very poor digit span.

primacy effect was preserved, but he had no recency effect.

P: Processing in STM is not required for LTM encoding

E: according to MSM, processing in STM is required for encoding into LTM

E: However, patient KF, with defective STM preserved LT learning and recall

P: MSM predicts that the longer an item is held in the short-term store, the greater the likelihood of long-term storage.

E: Rundus (1971) showed that rehearsing items in the short-term store does correlate with long-term retention

E: other factors such as depth of processing (Craik & Tulving, 1975) are far more important for determining whether information will be remembered

P: MSM assumes that STM and LTM are unitary, operating in a single, uniform way.

E:

E: Baddeley & Hitch (1974)

Warrington & Shallice (1972)

patient KF had worse STM for auditory letters and digits than for visual stimuli, suggesting that there may be distinct STM stores for different kinds of material.

Baddeley & Hitch (1974)

Using dual-task methodology, found that auditory rehearsal of digits did not affect the number of errors made in a concurrent grammatical reasoning task.

This was interpreted as suggesting that there may be a distinction between an auditory-verbal STM and a central information processing system involved in reasoning.