coding capacity and duration of memory☑️

coding

definition and research

the format information is stored in the memory stores/the process of converting information between different forms

research on coding:

alan baddely (1966) gave different lists of words to four groups of p’s to remember; either acoustically dis/similar or semantically dis/similar. p’s were shown the words and instructed to recall them. when instantly recalled (from STM), they tended to do worse with acoustically similar words, however after 20 minutes (from LTM), they did worse with semantically similar words, suggesting information is coded acoustically in STM and semantically in LTM)

evaluation of research on coding

-a clear difference is identified between the two separate memory stores + the matching between memory stores and word types is still used today (high temporal validity) + helped future psychologists develop theories (eg MSM)

-artificial stimuli (no meaningful material): words had no personal meaning to p’s so dont reflect much about coding in everyday life as when processing more meaningful information, semantic coding could be used for STM coding - limited application.

capacity

definition, research and evaluation

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

-joseph jacobs (1887) found STM capacity by measuring digit span. researcher reads out 4 digits and p recalls aloud in the correct order. if correct, researcher increases amount of numbers by one, indicating the individuals digit span. mean span found for numbers was 9.3 items, where for letters it was 7.3

evaluation of research on capacity

has been replicated, and his findings have been confirmed by other better controlled studies (bopp and verhaeghen 2005), suggesting his study is as valid test of digit span in STM

capacity

george miller

-memory+chunking span: george miller (1956) noticed everyday things come in 7’s (music notes, days of the week, deadly sins) and concluded STM span is 7+-2, while noting people can recall 5 words as easily as 5 letters, by chunking (grouping)

limitations: miller may have overestimated STM capacity; nelson cowan (2001) reviewed other research and concluded STM capacity is around 4+-1 chunks - proving his lower estimation to be more accurate than this higher one

research on duration of STM (trigram study)

research and evaluation

duration- the length of time information can be held in memory

margaret and lloyd peterson (1959) tested 24 students in eight trials each, where on each they were given a constant syllable (YCG) and a 3-digit number to count down from until told to stop (to prevent mental rehearsal + increasing STM memory). after three seconds, average recall was around 80% and 3% after 18 seconds. their findings suggest STM duration may be around 18 seconds, unless information is repeated (eg verbal rehearsal)

research on duration of STM

evaluation

-meaningless stimuli so not generalisable to most everyday activities (lacks external validity), however not completely irrelevant as we do remember pointless information like in the study (phone numbers), study lacks external validity.

-artificial lab environment encourages demand characteristics

research on duration of LTM

harry bahrick et al (1975) studied 392 american p’s aged 17-74 and obtained their yearbooks. recall was tested by; photo recognition with 50 photos, and free recall for all names in their graduating class.

findings: p’s tested within 15 years of graduating had 90% photo recognition accuracy, but after 48 years, recall declined to around 70%. free recall after 15 years was 60% and 30% after 48, showing LTM may last up to a life time for some material

evaluation on research of LTM duration

high external validity - researcher investigated meaningful memories, when LTM memory studies were conducted with meaningless pictures, rates were lower (shepard 1967), suggesting bahricks findings reflect a more real estimate of LTM duration

STM and LTM definitions

short term memory (STM): limited-capacity memory store with mainly acoustic coding, capacity is 5-9 items, on average, with an 18-second duration.

long term memory (LTM) - permanent memory store with mainly semantic coding, unlimited capacity and can have a lifetime duration.

types of long-term memory

-proposed by endel tulving (1985), after realising the MSM view of LTM was too simplistic and inflexible, where he said there are 3 LTM stores containing different types of information

-three types:

• episodic memory

• semantic memory

• procedural memory

episodic memory

-our ability to recall complex events from our lives (eg most recent dentist visit). they’re time stamped; you remember when these events happened, they also store information about how events relate to eachother in time.

-memory of a single episode include several elements; like behaviours, places and objects - which are all interwoven to produce a single memory

-remembering requires a conscious effort, usually quick but you’re still aware of the effort to remember

semantic memory

-contains shared knowledge of the world (combination of dictionary + encyclopedia); word definitions, how to apply to college, what an orange tastes like ect. a less personal type of memory store and more general to everyone

-not time-stamped; we don’t usually remember when we first watched moana, we just remember the plot

-contains an immense material collection

-less vulnerable to distortion and forgetting than episodic memory, according to tulving

procedural memory

-memory store dedicated for actions or skills.

-can be recalled without conscious awareness or much effort (like muscle memory)

-example: like driving a car, which becomes automatic through practice; gear changing and putting on indicators becomes instinct

types of long term memory

evaluation: strengths

clinical evidence

-case studies of henry molaison+clive wearing -men with severely impaired due to brain damage, but relatively unaffected semantic memories (they still understood the meaning of words eg he couldn’t recall stroking a dog 30m earlier but he didn’t need the concept of ‘dog’ explained to him. their procedural memory’s were also in tact (clive could still read music, sing and play the piano). this evidence supports tulvings view that there are different memory stores in LTM as one store can be damaged while the rest are unaffected.

counterpoint: studies on brain injuries can help researched understand how memory normally works but their flaws are they lack control of variables; the researcher has no knowledge of the individuals memory before the damage so measuring the deterioration is impossible. this lack of control limits what clinical studies can tell us about LTM.

-understanding types of LTM allows psychologists to help people with memory problems; eg memory deteriorates with age but research shows this is specific to episodic memory. recent and long term event recall becomes harder. sylvie belleville et al. (2006) devised an intervention to improve episodic memories in elderly people. the trained participants performed better in a test of episodic memory after training than a control group, proving that distinguishing types of LTM enables specific treatments to be developed.

types of long term memory

evaluation: weaknesses

conflicting neuroimaging evidence - buckner and petersen (1996) reviews evidence regarding the location of semantic and episodic memory, concluding that semantic memory is located in the left of the prefrontal cortex and episodic memory on the right. however other research links the left prefrontal cortex with encoding of episodic memories and the right prefrontal cortex with episodic retrieval (tulving et al 1994). this challenged any neurophysiological evidence to support types of memory as there is poor agreement on formation