coding capacity and duration of memory☑️

coding

definition and research

the process of converting information between different memory stores

baddely (1966) different word lists to 4 groups to remember; either acoustically dis/similar or semantically dis/similar. instant recall (from STM), was worse with acoustically similar words, and after 20 minutes (from LTM), was worse with semantically similar words, suggesting information is coded acoustically in STM and semantically in LTM

evaluation of research on coding

-identifies clear difference between the two separate memory stores, still used today (high temporal validity) + helped future psychologists develop theories (eg MSM)

-low mundane realism: no meaningful material so doesnt reflect everyday coding. when processing more meaningful information, semantic coding could be used for STM - limited application.

capacity

definition and research

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

-jacobs (1887) measured STM capacity through digit span. researcher reads out 4 digits and p recalls aloud in the correct order. if correct, researcher increases digits by one. mean span for numbers was 9.3 items, 7.3 for letters.

evaluation of research on STM capacity

replicated and confirmed by better controlled studies (bopp and verhaeghen 2005), suggesting study is a valid test of digit span in STM

capacity

-memory+chunking span: 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; cowan (2001) more accurately concluded STM capacity to be 4±1 chunks

research on duration of STM (trigram study)

research

the length of time information can be held in memory

margaret and lloyd peterson (1959) 24 student p’s, eight trials each, given a constant syllable (YCG) and a 3-digit number to count down from until told to stop (to prevent mental rehearsal increasing STM). after 3s, average recall was around 80% and 3% after 18s. suggest STM duration may be around 18 seconds without repetition or rehearsal

research on duration of STM

evaluation

-meaningless stimuli so not generalisable to everyday activities (low ecological validity + mundane realism ∴ external validity), not completely irrelevant as we remember pointless information like phone numbers.

-artificial lab environment prone to demand characteristics

research on duration of LTM

bahrick et al (1975) 392 US p’s 17-74. recall by photo recognition, and free recall for all names in their graduating class; tested by obtained yearbooks.

p’s within 15 years of graduating had 90% photo recognition accuracy. 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 - investigated meaningful memories. when LTM memory studies were conducted with meaningless pictures, rates were lower (shepard 1967), suggesting bahricks findings reflect a real estimate of LTM duration

STM and LTM definitions

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

long term memory (LTM) - permanent memory store with mainly semantic coding, unlimited capacity, suspected lifetime duration.

types of long-term memory

-tulving (1985) suggested the MSM view of LTM was simplistic and inflexible, and proposed 3 LTM stores containing different types of information

-three types:

• episodic memory

• semantic memory

• procedural memory

episodic memory

-recalls complex events from our lives (eg most recent dentist visit). time stamped; remember when they happened, and store information about how events relate to eachother in time.

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

-remembering requires a usually quick, conscious effort

semantic memory

-contains shared knowledge of the world (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

-tulving suggests its less vulnerable to distortion and forgetting than episodic memory

procedural memory

-memory store for actions or skills.

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

-example: driving car becomes instinctive through practice

types of long term memory

evaluation: strengths

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

counterpoint: no knowledge of the individuals memory before 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. belleville et al. (2006) elderly ps 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; elderly memory intervention

types of long term memory

evaluation: limitations

conflicting neuroimaging evidence - buckner and petersen (1996) conclude semantic memory is located in the left of prefrontal cortex with episodic memory on the right. however tulving et al (1994) link the left prefrontal cortex with encoding of episodic memories and the right prefrontal cortex with episodic retrieval. challenging any evidence to support types of memory as there is poor agreement on formation