Peterson and Peterson (Memory)

Peterson and Peterson (1959) Short-Term Retention of Individual Verbal Items (pg. 43-44) “Understand the aims, procedures and findings (results and conclusions), strengths and weaknesses of: Peterson and Peterson (1959) Short-term retention of individual verbal items” 

Background to the study: The Petersons wanted to test the duration of the short-term  memory store. The did this by preventing participants from rehearsing, by giving them an  interference task: counting backwards in threes.  

New term: A trigram is a set of three consonants, e.g. DVM.  

Description: APRC 

A• The Petersons aimed to test the duration of the short-term memory store.
P24 Psychology students from an American University were used as participants in  the study. • Each student was read a set of letters (a trigram: 3 consonants, e.g. FNL) to  remember. • Then, they were read a three-digit number. The participant then had to count  backwards from this number, in threes or fours. E.g. 709, 706, 703… to stop them  rehearsing the trigram. This is called an interference task. • When signalled by a red light, the participant was asked to recall the trigram. This  was after either 3, 6, 9, 12, 15 or 18 seconds of counting backwards.  • Each participant had 8 goes at each time delay, meaning they did the procedure 48  times in total with different trigrams! 
R• When counting backwards for 3 seconds, 80% got the trigram correct. • When counting backwards for 18 seconds, less than 10% got the trigram correct. 
C• The short-term memory store has a short duration of about 18 seconds, without  rehearsal.

The Petersons did a second experiment, using 48 students from the same University. This  time, half of the participants were allowed to repeat the trigram out loud, using vocal  rehearsal. The other half of the participants had to stay in silence, so they could only rehearse  the trigram in their head. They then had to do the counting backwards in threes task, as in the  first experiment. Those given the chance to vocally rehearse the trigram were more likely to  correctly recall the trigram, showing that rehearsal helps transfer information from the short term store to the long-term store.

Evaluation: GRAVE 

G• They only used 24 students, therefore the results may not reflect other people’s  memory.  • Students should have good memory, whereas older adults may have a worse  memory. 
R• The study had a standardised procedure (fixed timings for counting backwards) so  the study can be repeated to check consistency. 
A• The study is useful as it supports multistore model of memory’s claim that the  short term memory store has a short duration. • It shows us that we have to rehearse information if we want to remember it for  longer than about 18 seconds. 
V• The results have low ecological validity, as it was an artificial memory test of  trigrams. So it doesn’t reflect everyday memory recall of real events. 
E• There aren’t any ethical issues with the study as it was just a simple memory  experiment, that didn’t cause any harm to participants. 

Peterson and Peterson (1959) Key Term Glossary

Short term  memoryOur temporary memory store (< 30 seconds, acoustic encoding, 5-9  chunks)
Duration The amount of time information can be held in a memory store
Trigram Three consonant letters, e.g. GKL
Rehearsal Repeating information over and over again to help it store in the long term memory system (helps transfer from the STM to LTM)
Interference  taskA task that interferes with your ability to rehearse information
Need more help? Want to stretch your understanding? 
https://www.tutor2u.net/psychology/reference/duration-of-short-term-memory

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