AO3 The multi-store model of memory: sensory register, short-term memory and long-term memory. Features of each store: coding, capacity and duration

Sperling’s study of the sensory register method

Briefly displayed to his participants 3 rows of 4 letters. Then he trained participants to recognise three tones indicating to a row. The letters were presented again for 50 milliseconds each with a tone sounding immediately after to tell them which row to write down.

Sperling’s study of the sensory register findings

In the first part, participants could recalled 4 or 5 letters but reported they were aware of more. In the second part, he found participants recalled on average 75% of the letters from the cued row.

Sperling’s findings of the sensory register suggest

A large amount of information is available, so the capacity of the sensory register is very large, but it decays very rapidly, so the duration is very short.

Jacobs’ study into STM capacity method

Read out lists of digits, starting with 4 digits, asking participants to repeat them back to him. If correctly recalled then he read out 5 digits, repeating this until the participant couldn’t correctly recall the digits.

Jacob’s study into STM capacity findings

He found the mean digit span for numbers was approximately 9 items and for letters it was 7, which supports the idea that the capacity of STM is about 7 items.

Extraneous variables in Jacobs’ study into STM capacity

This is a very old study which means that may not have been as carefully controlled as would be the case with modern research. For example, perhaps some participants were distracted during the study, which would mean their digit spans were underestimated due to this extraneous variable.

Reliability of Jacobs’ study into STM capacity

Since 1887 the study has been replicated many times and the findings confirmed, meaning they are reliable and suggesting Jacobs’ study was a valid test of digit span in STM.

Miller’s chunking theory

Noticed that many everyday things such as days of the week come in 7s. This suggests that we can hold 7 ± chunks of information in STM. So if sets of letters are chunked together in some way we can remember more of them. However later research shows the larger the chunk the less may be remembered.

Peterson and Peterson’s study into duration of STM method

Participants were briefly shown trigrams of 3 consonants and asked to recall it after a period of 3, 6, 9, 12, 15, or 18 seconds. They were given an interference task of counting backwards in 3’s between the presentation of the trigram and recall, this was to prevent rehearsal.

Peterson and Peterson’s study in to STM duration findings

After 3 seconds, participants recalled 80% of trigrams, after 6 seconds, there was 40% recalled and after 18 seconds only 10% recall. This study supports the idea that the duration of STM is around 18 seconds.

Baddeley’s study into STM coding method

Participants were shown various lists of words and asked to recall them in the correct order.

Baddeley’s study into STM coding findings

When tested immediately after presentation it was found that more mistakes came from mixing up words that were acoustically similar rather than words that were semantically similar. This supports the idea that the main form of coding in STM is acoustic.

Highly controlled lab experiments studying STM

The IV was manipulated by the researcher and there was good control over extraneous variables, meaning cause and effect relationships can be established. The standardised procedures mean that each research study could easily be replicated by other researchers, allowing psychologists to assess the reliability of the findings.

Artificial environments in studies into STM

The tasks used in some of the research into STM were artificial and very different to everyday STM tasks. The research therefore lacks external/ecological validity, and we cannot be sure that the cause and effect relationships established would apply to everyday settings. But it can be argued that Miller’s research has higher ecological validity as learning short lists is normal STM use.

Bahrick’s study into LTM duration method

Showed participants names and faces of their classmates many years after they left school. Involved 392 ex-high school students aged 17 to 74 who graduated 2 weeks to 57 years ago. The first condition was free recall where participants had to recall the students name. The second condition was photo recognition where the participants had to sort 50 photos into those that were in their class or not.

Bahrick’s study into LTM duration findings

In condition 1, those who had graduated 15 years ago had 60% recall accuracy, whilst those who graduated 48 years ago have 30% recall accuracy. In condition 2, those who graduated 15 years ago had 90% accurate recognition whilst those who graduated 48 years ago had 60% accurate recognition.