1. coding, capacity and duration

coding definition

the format in which information is stored

research on coding

ALAN BADDELEY (1966)

• gave different lists of words to four groups of participants to remember

  1. acoustically similar

  2. acoustically different

  3. semantically similar

  4. semantically different

• participants were shown the original words and asked to recall them in the correct order

findings

• when they recalled the word list immediately, recalling from STM, they tended to do worse with acoustically similar words

• when they recalled the word list after a time interval of 20 minutes, recalling from LTM, they tended to do worse with semantically similar words

suggests information is coded acoustically in STM and semantically in LTM

evaluation of study on coding

1. separate memory stores

2. artificial stimuli

separate memory stores

• study supports idea of distinct STM and LTM as it found that STM encodes acoustically while LTM encodes semantically

• this distinction supports the multi-store model of memory

• and strengthens the understanding of how memory processes differ between STM and LTM

artificial stimuli

• study used artificial stimuli which limits ecological validity and real world application

• word lists had no personal meaning for the participants, meaning memory may work differently for meaningful information

• findings may not generalise to real life memory use

capacity definition

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

research on capacity (digit span)

JACOBS (1887) found out capacity by measuring digit span

• researcher reads out four digits and if the participant recalls them out loud correctly, the researcher reads out five digits and so on

• do this until participant cannot recall the order correctly, which indicated the individuals digit span

findings - the mean span for digits across all participants was 9.3, and for letters 7.3

strength of study

• study is valid and reliable

• it has been replicated despite early research limitations (BOPP et al 2005)

• consistent findings confirm the study’s accuracy, providing a reliable measure of STM span

research on span of memory and chunking

MILLER (1956) made observations of every day practice

• noted that things come in sevens eg seven notes on the music scale, seven days in a week

• thought the span (capacity) of STM is about seven items, plus or minus two

• also noted people can recall five words as easily as five letters which is done by chunking - grouping sets of digits or letters into units or chunks

limitation of research

• may have overestimated STM capacity

• research (COWAN 2001) suggests STM capacity is closer to four plus or minus one chunks

• means MILLER’s estimate of seven items may not be universally accurate

duration definition

the length of time information can be held in memory

research on STM duration

PETERSON & PETERSON (1959)

• tested 24 students in eight trials (tests) each

• on each trial the student was given a consonant syllable eg YCG to remember and also a 3 digit number. they would count back from this number until told to stop - done to prevent mental rehearsal which would increase duration

• on each trial they were told to stop after varying periods of time: 3, 6, 9, 12, 15 or 18 seconds (the retention interval)

findings

• after 3 seconds, average recall was 80%

• after 18 seconds, average recall was 3%

suggests STM duration may be about 18 seconds, unless information is repeated over and over

limitation of study

• lacks external validity

• study used artificial consonant syllables whereas everyday memory typically involves meaningful material

• makes study less applicable as results may not reflect real world memory processes

research on LTM duration

BAHRICK et al (1975)

• studied 392 american participants aged between 17 and 74 and had their high school year books obtained

• recall was tested in various ways

  1. photo-recognition test consisting of 50 photos with some from yearbook

  2. free recall test where participants recall all the names of their graduating class

findings

• those tested within 15 years of graduation were 90% accurate in photo recognition

• after 48 years recall declined to 70% for photo recognition

• free recall was less accurate than recognition - about 60% after 15 years, dropping to 30% after 48 years

suggests LTM may last up to a lifetime

strength of study

• high external validity

• study used real life meaningful memories like names and faces which is more realistic than studies with meaningless stimuli

• findings provide more accurate estimate of LTM duration