Duration, Capacity and Encoding

Question	Answer
Duration of STM	Duration - a measure of the length of time for which a memory can last before it is no longer available. STM has a limited duration, which may be somewhat enhanced by the process of maintenance rehearsal. If rehearsed enough, information may also be transferred to the LTM by rehearsal.
Duration of LTM	Duration - a measure of the length of time for which a memory can last before it is no longer available. LTM has a potentially unlimited duration. MEmories last anywhere from 2 hours to a lifetime.
Peterson and Peterson (1959)	Aim: To investigate duration of STM Procedure: 24 university student participants asked to recall a nonsense syllable and number sequence after a retention interval of varying lengths (3,6,9,12,15 or 18s) in which participants counted backwards in order to prevent rehearsal. Each participant given 2 practice trials and 8 trials. Findings: 90% recall with 3s interval, 2% recall with 18s interval Conclusion: STM lasts about 20s maximum.
Peterson and Peterson (1959) Evaluation	Low ecological validity - situation not highly reflective of real life settings Low internal validity - may not have been truly testing duration as counting backwards may have caused syllables to be displaced - therefore test of capacity. Contradictory evidence - Marsh et al. found duration is only about 2s when participants do not expect to be tested. However, Nairne et al (1999) found recall was possible after 96 seconds if tested on same items over all trials - information remains in STM for longer unless OVERWRITTEN
Shepard (1967)	Aim: To test duration of LTM Procedure: Participants shown 612 memorable pictures one at a time. One hour later they were shown pictures amongst others and asked to recall which they had previously seen. Findings: One hour later, participants showed almost perfect recognition. WHen tested again 4 months later there was still 50% recognition. Conclusions: recall for memorable material is long lasting, though seems to reduce slightly over time.
Shepard (1967) Evaluation	Low ecological validity - contrived situation makes findings hard to generalise to real life situations as is lacking in mundane realism. Supporting evidence - Bahrick et al. (1975) found 70% accuracy in matching names to faces after 48 years.
Bahrick et al. (1975)	Aim: to demonstrate the considerable duration of LTM Procedure: 392 US participants who had left high school between 1 and 48 years ago were tested for recall of their classmates through, free recall, photo recognition and matching names to photos. Findings: 48 years from leaving high school there was 70% accuracy in matching names to photos and 30% accuracy of free recall. There was no large decrease in ability photo recognition over time though free recall did somewhat diminish. Conclusions: LTM can store some types of information for a very long (potentially unlimited) time.
Bahrick et al. (1975) Evaluation	High ecological validity - study used naturalistic material so had higher mundane realism Low generalisability - material used had high level of significance to participants and there was great opportunity for rehearsal so findings may not be generalisable to other memory tasks. Low population validity - all participants were American so may not be highly representative of the entire target population.
Capacity of STM	Capacity - A measure of the amount of information that can be held in the memory, often measured in chunks of information such as digits and numbers. STM has a limited capacity - suggested to be restricted to around 7 chunks. Digit span technique - a method of measuring capacity of STM whereby a participant looks at and then attempts to recall an increasing number of digits until s/he can no longer do so correctly.
Miller (1956)	Aim: To investigate the limitations of the STM in terms of capacity Procedure: Conducted a review of psychological research Findings: the capacity of STM is likely to be limited to 7 digits plus or minus 2. He also found that people are able to recall just as many words as letters Conclusions: STM has a limited capacity, but can be enhanced by the process of 'chunking' whereby we group pieces of information into meaningful chunks such that more can be remembered.
Miller (1956) Evaluation	Contradictory evidence - Simon (1974) found that memory span decreased for larger chunks i.e less 8 word phrases could be remembered than one syllable words - chunking is limited as to how much it may enhance the capacity of STM Real world application - British postcode system uses chunking in order to make the postcodes more easily remembered. Contradictory evidence - Cowan (2001) found capacity of STM likely to be limited to 4 chunks, suggesting it was more limited than MIller had found.
Jacobs (1887)	Aim: to assess the capacity of STM using digit span technique. Procedure: used digit span - participants shown a series of digits and asked to recall them in order, each trial another digit was added until participants could no longer correctly recall them FIndings - The average span for numbers was 9.3 whilst for letters it was 7.3. Digit span also appeared to increase with age, being just 6.6 for 8 year olds but 8.6 for 19 year olds. Conclusions - numbers are more easily recalled as there are only 9 existing numbers whilst there are 26 letters. Increasing brain capacity and development of memory strategies may explain effect of age on capacity of STM.
Jacobs (1887) Evaluation	Low ecological validity - task not reflective of many real life memory requirements (apart from possibly remembering phone numbers) Supporting evidence - Miller (1956) found capacity of STM to be limited to approximately 7 digits. Low historical validity - Conducted in 1887, now we are likely to have more advanced memory improvement techniques etc (e.g chunking) Contradictory evidence - Cowan (2001) conducted a far more recent study and found the capacity of STM to be limited to 4 chunks
Cowan (2001)	Aim: to investigate the capacity of STM Procedure: Conducted a review of a variety of studies into the capacity of STM Findings: capacity is likely to be limited to around 4 chunks Conclusions: the capacity of STM is more limited than previously suggested
Cowan (2001) Evaluation	Supporting evidence - Vogel et al. (2001) investigated the capacity of STM for visual stimuli and also found it was limited to 4 chunks.
Capacity of LTM	Capacity - a measure of the amount of information that can be held in the memory LTM has a potentially unlimited capacity.
Encoding in STM	Encoding - the altering of information such that it is able to be stored in the memory in various forms/codes. Usually either visually, acoustically, or semantically. Information is encoded mainly acoustically - in terms of how it sounds - in the STM.
Encoding in LTM	Encoding - the altering of information such that it is able to be stored in the memory in various forms/codes. Usually either visually, acoustically, or semantically. Information is encoded mainly semantically - according to its meaning - in the LTM
Baddeley (1966)	Aim: to assess the effects of semantically and acoustically similar words on STM and LTM recall Procedure: participants were given a lost of 5 words which were either semantically similar or dissimilar or acoustically similar or dissimilar, and asked to recall them. Findings: participants had difficulty remembering semantically similar words in the LTM but not STM and acoustically similar words in the STM but not LTM Conclusions: STM generally relies on acoustic encoding whilst LTM uses semantic encoding.
Baddeley (1966) Evaluation	Acoustic codes not the only method of encoding in STM - Brandimore et al (1992) found visual encoding was used if the stimulus was visual and verbal rehearsal was prevented during the retention interval. (in order to prevent translation into verbal code) Semantic codes not only method of encoding in LTM - Frost (1972) found that LTM recall could be enhanced by visual as well as semantic categories suggesting some of the information had been encoded visually.
Baddeley (1966b)	Aim: to investigate encoding into the LTM Procedure: modified original 1966 experiment to focus solely on LTM. Participants were shown a list of 10 words from one of the four categories four times and tested for recall 20 minutes later, rehearsal having been prevented. Findings: Recall for semantically similar words decreased significantly Conclusions: LTM uses primarily semantic encoding
Baddeley (1966b) Evaluation	Contradictory evidence - Frost (1972) found evidence of visual encoding in LTM and Nelson and Rothbart (1972) found evidence of acoustic encoding Low generalisability - only tested memory for words, not any other type of stimulus so findings may not be generalisable to other types of memory task.
Conrad (1964)	Aim: to investigate the method of encoding into STM Procedure: participants shown a list of 6 acoustically similar consonants followed by a list of 6 acoustically dissimilar consonants and asked to write each down (recall) Findings: more errors were made in recalling acoustically similar words than acoustically dissimilar words Conclusions: STM uses primarily acoustic encoding.
Conrad (1964) Evaluation	Low ecological validity - recall task of single consonants not highly reflective of real life situations giving the study low mundane realism so less generalisable to other non laboratory settings. Low internal validity - does not consider other possible methods of encoding as only tests acoustically similar and dissimilar words therefore cannot conclude that acoustic is the only method of encoding into STM Supporting evidence - Baddeley (1966) used similar procedure and also concluded STM uses acoustic encoding i.e results are reproducible.

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Duration, Capacity and Encoding

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	Created by Catherine Kidd almost 10 years ago