memory 1 Flashcards
Outline the meaning of short term memory (STM).
STM is the capacity of the brain to hold a small amount of information for a short period of time. STM is the limited-capacity memory store (5 - 9 items on average). The duration of STM is about 18 - 30 seconds. Encoding of information is primarily acoustic.
Outline the meaning of long term memory (LTM).
The permanent memory store. The capacity of long term memory could be unlimited. Duration can be anything from a few minutes to a lifetime. Encoding of information is primarily semantic (meaning).
Describe the meaning of capacity.
The amount of information that can be stored in memory at any one time. Miller (1956) found STM has a capacity of 7 +/-2 items. LTM capacity is potentially unlimited.
Describe the meaning of duration.
The length of time information can be held in memory. Peterson and Peterson (1959) found STM has a duration for roughly 30 seconds. Bahrick (1975) found LTM has a potentially unlimited duration.
Describe the meaning of coding.
The format in which information is stored in various memory stores. STM is normally coded acoustically and LTM is normally coded semantically.
Outline Jacobs’ (1887) research on capacity.
Jacobs (1887) measured digit span.
Participants were given a sequence of digits and then asked to recall them out loud in the correct order.
The sequence was increased by one each time until the participant could no longer recall the sequence.
The mean span was 9.3 for numbers and 7.3 for letters.
Evaluate Jacobs’ (1887) research on capacity.
One strength of Jacobs’ study is that it has been replicated.
An old study is very old and is likely to have been poorly controlled.
Participants may have been distracted and performed worse.
This may reduce the validity of the research due to poorly controlled confounding variables, e.g. the longer the digit sequence the more time there is to get distracted.
The results of this study have been supported by further research supporting its validity.
Evaluate Miller’s (1956) research on capacity.
Miller (1957) suggested that the number of items that could be held in short term memory was 7 (plus or minus 2). Miller based his ideas on the prevalence of seven in human evolution (7 days of the week, seven deadly sins etc).
Miller also noted that people can recall 5 words as well as 5 letters. This is because people can chunk information into one item.
Miller may have overestimated the capacity of STM.
Cowan (2001) reviewed other research and concluded that the capacity of STM was only 4 chunks. This suggests Miller’s lower estimate of 5 is more appropriate.
Evaluate research on the duration of STM.
Meaningless stimuli. The material used was artificial - nonsense trigrams do not represent real life.
Lack of external validity.
Forgetting can be explained by: spontaneous decay - if the information is not rehearsed the memory trace simply disappears, or displacement - new information pushes old information out due to the limited capacity of STM.
Evaluate research on the duration of LTM.
Bahrick et al (1975) studied 392 participants from age 14 - 74.
Participants were asked to recall ex-school friends via: a photo recognition test of 50 pictures; a free recall test where they recalled the names of all people from their graduate class.
Photo recognition was 90% accurate after 15 years and 70% accurate after 48 years and free recall was 60% accurate after 15 years and 30% accurate after 48 years.
Real life memories were studied which gives this study a high external validity.
Studies with meaningless information such as Shepard (1967) have much lower recall rates.
It is hard to control confounding variables in this study, e.g. participants are likely to have looked at yearbook photos and rehearsed their memory over the years.
Evaluate research on coding.
Baddeley (1966a, 1966b) gave different word lists to four different groups. The word lists were: acoustically similar, acoustically dissimilar, semantically similar, semantically dissimilar. Participants had to recall the words immediately and after a period of time.
Participants did worse immediately with acoustically similar words.
Participants did worse after 20 minutes with semantically similar words.
The study suggests we encode STM acoustically and LTM semantically.
This study has been criticised for using artificial stimuli. This suggests it lacks external validity and so the findings cannot be generalised, e.g. it is highly likely meaningful material is encoded semantically in STM.
