coding, capacity and duration

what is coding

the format in which information is stored in various ways

what is capacity

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

what is duration

the length of time that information can be held in memory

what is short term memory

the limited-capacity memory store

what is the coding, capacity and duration of STM

coding is mainly acoustic (sound), capacity is an average of 5-9 items, duration is about 18 seconds

what is long term memory

the permanent memory store

what is the coding, capacity and duration of LTM

coding is mainly semantic (meaning), capacity is unlimited, duration is up to a lifetime

who researched coding

Baddeley (1966)

what was the procedure of Baddeley’s research and what did this suggest

he gave a list of words to 4 participant groups to remember and then recall in the correct order:

1) acoustically similar words

2) acoustically dissimilar words

3) semantically similar words

4) semantically dissimilar words

STM (immediate recall) - tended to do worse with acoustically similar words

LTM (recall after 20 mins) - tended to do worse with semantically similar words

this suggests that information is coded acoustically in STM and semantically in LTM

who researched capacity

Jacobs (1887) and Miller (1956)

how did Jacobs research capacity

he developed the technique to measure digit span in which a researcher will provide a set of digits and ask the participant to recall these out loud in the right order

the number of digits is increased each time until the participant can no longer recall them (determines the individuals digit span)

Jacobs found that the mean digit recall was 9.3 items and for words it was 7.3 items

how did Miller research capacity

he made everyday observations and concluded that things come in 7s (e.g. days of the week and music scales) so thought that the capacity of the STM must be 7 items (±2)

what did Miller also conclude about chunking

Miller also observed that people can recall 5 letters as well as they can recall 5 words and this is done by chunking (grouping sets of letters or digits into chunks)

who researched duration (2 separate occasions)

Peterson and Peterson (1959) and Bahrick (1975)

how did Peterson and Peterson research duration and what did this suggest

they tested 24 undergraduate students who each took part in 8 trials (tests)

on each trial the students were given a trigram (consonant syllable e.g. YCG) to remember as well as a 3 digit number that they had to count back from until told to stop to prevent mental rehearsal of the consonant syllable

on each trial the students were told to stop counting after different amount of time (3,6,9,12,15 or 18 seconds) - retention interval

findings show that the longer the retention interval the lower the rate of recall - showing that the duration of STM is very short unless if the item is rehearsed

how did Bahrick research duration and what does this show

he studied 392 participants from Ohio aged 17-74 using high school yearbooks that were obtained either from the participants of the schools

recall was tested in 2 ways:

1) photo recognition test consisting of 50 photos (some from yearbooks)

2) free recall where participants recalled names from their graduating class

her found that within 15 years of graduating photo recall accuracy was 90% whereas free recall was about 60% accurate

he also found that 48 years after graduating photo recall accuracy declines to 70% whereas free recall declines to 30%

this shows how long the LTM can last for

what is a limitation of research into coding

Baddeleys research used rather artificial stimuli rather than meaningful materials (list of words had no meaning to participants)

means we should be cautious about generalising this to different kinds of memory tasks - therefore has limited application

what are 2 limitations of research into capacity

1) Jacobs’ study lacks validity due to its early completion in which there was little control over studies meaning that confounding variables could’ve affected results

however other studies have supported the findings and therefore its validity

2) Miller may have overestimated the STM capacity - e.g. Cowan (2001) researched chunks and found that the STM has the capacity for about 4 chunks - suggests that the lower end of Millers’ chunks assumptions (5) was more accurate than 7

what is a limitation of research into duration (Peterson and Peterson)

the stimuli used in Peterson and Peterson’s research was artificial and doesn’t reflect real-life memory (lacks external validity)

what is a strength of research into duration (Bahrick)

high external validity as real life meaningful memories were studied