MSM- research into coding, capacity and duration

What did SPERLING (1960) research

Sensory register - capacity and duration of iconic memory

Procedure of Sperling (1960)

Participants shown 3x4 grid of 12 letters, after display disappeared were asked to recall as many letters. 2 conditions, same group:

- whole report- recall letters after shown whole thing

- partial report- tone heard immediately after display (high pitch= top row, etc.) only recall indicated row

Sperling's findings

- Whole report- only recall 5-12 letters

- Partial report- cued immediately could recall 3-4 letters from row (9-12 total), when cue delayed by 0.5s recall dropped sharply

Conclusions from Sperling's report

Sensory register (especially iconic memory) cn hold large amount of info

Memory fades within 200-250 ms

Matches capacity/duration in MSM

Evaluation of Sperling's study

Supports existence of brief high capacity sensory memory store

Low ecological validity- dont reflect visual memory IRL, so limits how applicable results are

Lack of consideration for individual differences- challenges validity (generalised)

What did JACOBS (1887) study

Capacity of STM

Jacob (1887) procedure

Sequences of digits/letters increased in length by 1 item at a time. Asked to repeat sequences in correct order immediately after presentation. Measured no. Digits/letters recalled in correct order

Jacob's findings

Average digit span: 9.3 items

Average letter span: 7.3 items

Digits recalled better than letters

Conclusions from Jacob's report

STM has limited capacity- 5-9 items

Supports idea of a capacity limited store in the MSM

Evaluation of Jacob's study

- supported by other studies (Miller's 7+-2), improves reliability

- supports by concept of chunking

- narrow methodology- may not reflect full scope of STM- oversimplifies

What did Peterson & Peterson (1956) study

Duration of STM when rehearsal is prevented

Peterson & Peterson procedure

-Presented Ps with consonant trigrams (e.g. CDX)

-Ps were asked to count backwards in 3s from a specified number (e.g.

451). This was to prevent rehearsal.

- After intervals of 3-18 seconds Ps were asked to stop counting and recall the trigram

lab experiment

Peterson & Peterson findings

-Ps were able to recall about 80% of the trigrams correctly after an interval of 3 seconds, but recall became progressively worse as the time intervals increased.

-After 18 seconds they could recall fewer than 10% correctly.

Conclusions from P&P report

STM has a very limited duration- into fades within 18s if not rehearsed

SupportsMSM idea of a temporary, short duration memory store

Evaluation of Peterson&Peterson study

Highly controlled lab experiment - standardising procedure and adding distraction task allowed to accurately measure duration of STM, so more likely to reflect IRL

Artificial task reduces ecological validity

Counting tasks may have caused interference instead of blocking rehearsal, so may have actively displaced trigrams from memory- hard to determine forgetting due to decay or interference- weakens study ability to isolate true cause of forgetting in STM

What did BADDELEY (1966) study

The differences in encoding between STM and LTM

Baddeley procedure

71 participants randomly allocated 1/4 conditions, presented with lists of monosyllabic words that were acoustically similar or semantically similar, asked to recall in correct order either immediately (test STM) or after time delay of 20 mins (LTM). Baddeley measured no. Correct words

Baddeley (1966) findings

STM- worse recall with acoustically similar than with acoustically dissimilar words

LTM- worse recall with semantically similar than with semantically dissimilar words

Baddeley (1966) conclusions

STM primarily encoded acoustically, LTM semantically

Supports idea that STM and LTM are separate memory stores with different characteristics

Evaluation of Baddeley (1966) study

- well controlled experimental design-increases findings validity, more confident results due to type of encoding instead of other variables

- artificial material use- low ecological validity- may not generalise well to encoding real world memories

- may oversimplify coding- later research shown both stores can use multiple types of coding, challenges idea of separate encoding types- study too narrow in conclusions

What did Bahrick et al (1975) study

Duration of LTM using meaningful, real-life material

Bahrick et al (1975) procedure

392 American peeps aged 17-74 tested on their memory of high school classmates using 2 key memory tests:

1- photo recognition- shown photos from yearbook and asked to identify

2- free recall- asked o name all classmates could remember (no visual cues)

Bahrick et al (1975) findings

1- photo recognition: 90% accuracy after 15 years, 70% accuracy after 48 years

2- free recall: 60% accuracy after 15 years, 30% accuracy after 48 years

Bahrick et al (1975) conclusions

LTM can last many decades, especially if material is meaningful, supports idea that LTM has a very long duration, perhaps even lifetime retention

Bahrick et al (1975) evaluation

- high ecological validity- uses real-life memories so findings are more applicable to everyday memory use

- major limitation is presence of confounding variables, especially opportunity for rehearsal (may have met up, revisited y.b. Etc.), so study may have tested effect of repeated retrieval, reducing validity

- highly meaningful material used so may not generalise to all types of LTM- limits validity