Coding capacity and duration of memory

Capacity

The amount of information that can be held in a memory store

Coding

The Forman in which information is stored in the various memory stores

Duration

The length of time information can be held in memory

Long term memory (LTM)

The permanent memory store, can store memories up to a lifetime

Semantic coding

Relies on meaning and understanding of material - dominant in long term memory

Short term memory (STM)

The limited capacity memory store - has capacity between 5-9 items on avarage, during 18 seconds

Acoustic coding

Encoding information based of of sounds, dominant in short term memory

Two main types of memory

Long term memory and Short term memory

The process of converting information between differnt forms is?

Coding

Alan Baddeley research on STM and LTM

gave different lists of words to 4 groups to remember

1. Acoustically similar

2. Acoustically dissimilar

3. Semantically similar

4. Semntaically dissimilar

• participants where asked to recall them

• from short term memory they did worse with acoustically similar words

• with long term memory they did worse with semantically similar words

What did Alan Baddeley’s research suggest

Information is coded acoustically in the short term memory (STM) and semantically in the long term memory

Strength of Baddeley’s study

Identified a clear difference between 2 memory stores

Limitation of Baddeley’s study

• The study used quite artificial stimuli rather than meaningful material

• So not relevant to everyday life, as information has no personal meaning to participants

Joseph Jacob’s and digit span

• Researcher reads out four digits and the participants recall these out loud in the correct order

• the researcher reads out 5 digits and so on until the participant cannot recall the order correctly = indicated individuals digit span

Average digit span

JACOB found that the mean digits across al participants was 9.3 items

• mean span for letters was 7.3

What is chunking

Grouping sets of digits or letters into units or chunks

Duration of STM - Margret and Lloyd Peterson

• tested 24 students in 8 trials each

• students where one a consonant syllable to remember as well as a 3 digit number = had to count backwards to prevent mental rehearsal

• on each trial they where told to stop counting backwards after varying periods of time

• after 3 seconds average recall was 80%, after 18 seconds avarage recall was 3%

What did Petersons findings suggest about STM duration

That STM duration may be about 18 seconds

• unless we repeat information over and over (verbal rehursal)

Limitations of Petersons study

• results may be due to interference (counting backwards) and not decay

• Conclusions about duration of STM may not be valid

Duration of LTM - Bahrick et al

392 American participants ages 17-74

• recall from a hig school yearbook through

1. Photo recognition

2. Free recall

Participants tested within 15 years of graduation where about 90% accurate in photo recognition, after 48 years recall declined to 70%

Free recall was less accurate than recognition

What did Bahrick et Al’s research suggest

Long term memory may last up to a lifetime for some memories.

Strength of Bahrick Et Al’s study

High external validity

• researcher investigated meaningful memories, so recall rates will be higher

• Reflect a more ‘real’ estimate of the duration of LTM