Memory

Memory

1. Coding, Capacity and Duration of Memory

   • Baddeley (1966) - Coding in STM and LTM
     • Four different groups given four different lists of words: acoustically similar or dissimilar and semantically similar or dissimilar
       • Findings: STM is coded acoustically. LTM is coded semantically
       • Findings: STM coded acoustically and LTM coded semantically
         • Limitation - material had no personal meaning to participants. When processing meaningful info people may use semantic coding for STM. Results have limited application
   • Research on Capacity of STM: Jacobs (1887)
     • Procedure of digit span: researcher reads out 4 digits and increases until the participant can't correctly recall the digits
       • Findings: participants can correctly recall 9.3 numbers and 7.3 letters in correct order from STM
   • Research on Capacity of STM: Miller (1956)
     • Miller noted that things come in sevens eg 7 s
   • Jacobs (1887) - Capacity of STM
     • Digit span:researcher reads 4 digits and increases until participant can't correctly recall digits
       • Findings: correctly recalled (on average) 9.3 numbers and 7.3 letters
         • Limitation - old. Early research lacked control of extraneous variables. Results may not be valid because there were confounding variables. Strength - results have been proved in other research, supporting its validity
   • Miller (1956) - Capacity of STM
     • Miller observed that most things come in sevens eg seven deadly sins and days of the week etc
       • Findings: Span of STM is about 7 items + or - 2 but can be improved by chunking - grouping sets of digits into units
         • Limitation- May have overestimated STM's capacity. He concluded capacity was 4 chunks which means 5 is a more appropriate estimate
   • Peterson and Peterson (1959) - Duration of STM
     • 24 students given trigrams (eg YCG) to remember and and a 3 digit no. to count down from for 3, 6 , 9 , 12, 15 or 18 secs
       • On average 80% recalled syllables correctly with a 3 sec interval. After 18 seconds it fell to about 3%, suggesting the duration of STM without rehearsal is 18-30 secs
         • Limitation - Artificial stimulus - lacks external validity. Strength - We remember meaningless things irl eg phone nos.
   • Bahrick et al (1975) - Duration of LTM
     • 392 Americans aged 17-74. !. Recognition test: 50 pics from their HS yearbook. 2. Free recall test: List names of their graduating class
       • Those tested within 15 years of grad. 90% accurate in photo recognition. After 48 years, recall declined to 70%. Free recall 60% accurate for those within 15 years of grad. dropping to 30% after 48 years
         • Strength - high external validity. Real life meaningful memories were used. When meaningless stimuli is used recall is lower (Shepard 1967). However confounding variables aren't controlled eg participants may have looked at pics before study

2. Multi-Store Model of Memory (MSM)

   • Theory proposed by Atkinson and Shiffrin (1968). There are separate memory stores and it describes how info flows through the memory system
     • Sensory Register (SR) - Stimulus from the environment passes into the SR. This is five stores - one for each sense - echoic for auditory info and iconic for visual info. Duration - less than a second. Capacity - high. Coding - depends on sense
     • Transfer from SR to STM - attention needs to be paid to be passed on
     • STM - limited capacity and duration store. Duration - 18-30 secs unless info is rehearsed. Capacity - 5-9 items. Coding - acoustic
     • Transfer from STM to LTM - Maintenance rehearsal allows info to pass onto the LTM if it is rehearsed for long enough
     • LTM - permanent memory store. To recall something from the LTM it has to be passed to the STM through a process called retrieval. Duration - potentially lifelong. Capacity - potentially unlimited. Coding - semantic
   • Strength - supported by research showing STM and LTM are different - Baddeley's research supports that the two memory stores are separate and independent
   • Limitation - more than one type of STM. Refer to KF study. The WMM is a better explanation
   • Limitation - only explains one type of rehearsal. Craik and Watkins (1973) said there is also elaborative rehearsal which is needed for LTM storage this occurs when you link info to your existing knowledge. Serious limitation because this finding can't be explained by the MSM
   • Limitation - artificial materials. Lacks external validity as it doesn't reflect how memory works in everyday life
   • Limitation - oversimplifies LTM. Research suggests it isn't a unitary store. It has semantic and episodic stores which aren't represented in the MSM

3. Types of LTM

   • Episodic memory - stores events from our lives. Episodic memories are time stamped - you remember when they happened. They involve several elements such as people, place, objects etc. You have to make a conscious effort to recall them
   • Semantic memory - stores our knowledge of the world. These memories are not time stamped, eg we don't remember when we first learnt of Justin Bieber. Semantic knowledge is less personal and more bout knowledge we all share
   • Procedural Memory - stores memories for actions and skills. These are memories of how we do things eg swimming. Recall occurs without awareness or effort. We might find these skills hard to explain to someone else
   • Strength - episodic memory supported by case studies of HM and Clive Wearing. Both had bad episodic memories - Clive couldn't recall events in his life yet he could play the piano perfectly. Supports the view that there are different LTM stores and one can be damaged and the others can be unharmed
   • Strength - Brain studies show that there are multiple stores. Tulving (1994) had people perform different tasks while their brains were being scanned . The stores are located in different areas of the brain. This shows a physical reality in the brain to the different types of LTM. Supports its validity
   • Strength - identifying different stores has real life applications. Belleville et al (2006) found episodic memories can be improved in the elderly with mild cognitive impairment. This is a strength because it allows specific treatments to be developed

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