Cognitive Flashcards
Capacity of STM - Millers Magic 7 (1956)
Capacity of STM - limited
Miller noticed in everyday practice that things come in sevens such as notes on a musical scale, days of the week, the deadly sins etc
He concluded that the capacity of the STM was about 7 items (plus or minus 2) and this could be increased by chunking - groups sets of digits/letters together into meaningful units
Capacity of STM - Jacob’s (1887) digit span test
Researcher reads 4 digits and increases by one each time until the ptp cannot correctly recall all of them. The final number of digits correctly recalled is their digit span.
On average ptps could recall 9.3 numbers and 7.3 letters in the correct order immediately after they were presented.
Strength of Jacob’s study - replicable
It’s an old study so may have lacked adequate controls such as confounding variables eg ptps being distracted. Despite this Jacob’s findings have been confirmed in later controlled studies eg Boop and Verhaeghen 2005) shows Jacob’s study is a valid measure of STM digits span.
Weakness of miler magic 7 - overestimates STM capacity
Jacob’s research does support millers however Cowan (2001) reviewed other research and concluded that the capacity of STM was only about 4 (plus or minus 1) chunks. This suggests that the lower end of Millers estimate (5 items) is more appropriate than 7 items.
Capacity of LTM
Potentially unlimited
Duration of STM
Limited duration - seconds. Info can be kept in for longer through rehearsal
Duration of STM - Peterson and Peterson (1959) Trigrams
24 psych students were given trigrams to recall and a 3 digit number to count backwards from in 3s or 4s to prevent rehearsal. The retention interval was varied - 3,6,9,12,15 or 18 seconds.
After 3 seconds the average recall was around 80% and after 18 seconds it was 3%. STM duration without rehearsal is up to 18 seconds.
Weakness of Peterson and Peterson study - uses meaningless stimuli
The recall of trigrams does not reflect meaningful everyday memory tasks so therefore the study lacks external validity.
Duration of LTM - Bahrick et al (1975) Yearbook photos
Ptps were 392 Americans aged between 17 and 74
1 - recognition test - 50 photos from high school yearbook
2 - free recall test - ptps listed names from their graduating class
Findings - recognition test - 90% accurate after 15yrs and 70% accurate after 48yrs
Free recall test - 60% accurate after 15yrs and 30% accurate after 48yrs
Free recall ability decreases with age to a large extent
Strength of Bahrick et al (1975) study - high external validity
Uses everyday meaningful memories eg peoples faces and names . When lab studies done with meaningless pictures to be remembered recall rates were lower - Stephenson 1967. Means that Bahrick et als findings reflect a more ‘real’ estimate of duration of LTM.
Coding in STM
Acoustically
Info is stored in memory in different forms depending on the memory store. The process of converting information between different forms is called coding.
Coding in LTM
Semantically
Coding in STM and LTM - Baddely (1966) acoustic and semantic
Gave different lists of words to four different groups of people
- acoustically similar (eg cat, cab, can) or dissimilar (eg pit, few, cow)
- semantically similar (eg great, large, huge) or dissimilar (eg good, huge, hot)
Immediate recall worse with acoustically similar words. STM is acoustic
After 20 mins worse with semantically similar words. LTM is semantic
Strength of Baddeleys study - used controlled conditions
Study had controls in place to prevent extraneous variables from confounding the results eg poor hearing - hearing test and only used people worth perfect scores. The experiment took place in controlled conditions in lab.
Limitation of Baddeleys study - used artificial stimuli
Words used had no personal meaning to ptps so tells us little about coding for everyday memory tasks. When processing more meaningful information people use semantic coding even for STM. Means the findings of this study have limited application.
MSM - Atkinson and Shiffre (1968)
The MSM describes how information flows through the memory system. Memory is made of three unitary stores that vary in encoding, duration and capacity.
MSM - Sensory register
All stimuli from the environment passes into the sensory register. It 5 memory stores one for each sense eg echoic - codes acoustically and iconic - is visual.
Coding - modality - specific, depends on the sense (visual in iconic, acoustic in echoic etc)
Duration - very brief, less than half a second
Capacity - very high
The sensory register holds an image for a few seconds while it is scanned to decide if attention should be paid and passed on through the system for further processing
MSM - transfer from SR to STM
Info passes further into memory only if attention is paid to it (attention is the key process)
MSM - STM
A limited capacity store of Temporay duration
- coding - acoustic
- duration - about 18 seconds unless info rehearsed
- capacity - between 5 and 9 (7 plus or minus 2) items before some forgetting occurs
MSM - transfer from STM to LTM
Maintenance rehearsal occurs when we repeat material to ourselves. We can keep info in STM as long as we rehearse it. If we rehearse it long enough it goes into LTM.
MSM - LTM
A permanent memory store
- coding - mostly semantic
- duration - potentially up to a lifetime
- capacity - potentially unlimited
MSM - retrieval from LTM
When we want to recall info from LTM it has to be transferred back to the STM by a process called retrieval
Limitation of MSM - evidence suggesting there is more than one store
Shallice and Warrington 1970 studied KF who suffered brain injuries after a motorcycle accident. His STM recall for digits was poor when he heard them but much better when he read them. He had trouble with verbal STM not visual STM. Other studies confirm there may be seperate STM stores for non-verbal sounds eg noises. So MSM is wrong to claim there is only one store of STM processing different types of information.
Support - Glanzer and Cunitz 1966 primary and recency effect
Words are better recalled from beginning - primary effect and end of a list - recency effect. In the primary effect words go to LTM. In recency effect - words are in STM and start of recall. Support for separate STM and LTM stores
Limitation of MSM - prolonged rehearsal is not needed for STM to LTM transfer
Craik and Watkins (1973) argued there are two types of rehearsal called maintenance and elaborative. Maintenance is the one described in the multistore model. but elaborative rehearsal is needed for long-term storage. This occurs e.g. when you link information to your existing knowledge or think about its meaning. This suggest that the multistore model does not explain how long term storage is achieved.
Strength of MSM - linear way - seoville and Milner (2006)
Case study of HM - he suffered from epilepsy and underwent brain surgery to remove part of his temporal lobes and hippocampus. It alleviated his epilepsy but left him of severe memory deficits although his IQ remained above average. he could not form long-term memories. this suggests hippocampus may function as a memory gateway memories must pass through before entailing permanent storage.
Types of LTM - episodic
It refers to ability to recall events from our lives like a diary of personal experiences. Eg what you had for breakfast this morning. They are complex memories as they are time stamped so you remember when they happened and how they relate in time. They involve several elements like people, places, objects and behaviours are woven into one memory. You have to make a conscious effort to recall them. Declarative
Research for episodic memory - clinical evidence
People who had brain damage to hippocampus and have memory deficits - Clive wearing and HM. Both had severely impaired episodic memory as a result of amnesia. Semantic memories were relatively unaffected as still knew meaning of words. HM could not recall stroking a dog an hour ago but would never need the concept of a dog explained to him. Procedural memory also intact as both knew how to tie shoelaces. Shows evidence of the seperate types. However there memories can’t be compared to how they were before the injury so can’t see how much worse it is - lack of control variables.
Types of LTM - semantic
Memories for meaning of the world and understanding eg like a dictionary. Contains knowledge of concepts and words eg animals. The memories are not time stamped eg we don’t remember when we first learnt about the film frozen. They are less personal than episodic memories and more about facts and knowledge we all share.
Research for semantic LTM - brain scan evidence Tulving
Brain scan evidence - tulving 1989 - injected himself with particles of radioactive gold to track brain blood flow in scanner when he was thinking of historical facts blood flow increased at back of brain but when thinking of childhood experiences blood flow increased at the front. Two different places for semantic and episodic memories shows there are different types.
Types of LTM - Procedural
Stores memories for actions and skills, memories of how we do things eg driving a car. Recall occurs without awareness or effort. These skills or actions become automatic with practice. Explaining a step by step procedure eg changing gear is hard because you do it without conscious recall.
Research for procedural LTM - corkin 1968 - HM
Studied HM with serious anterograde amnesia and was unable to store LTM. Taught new motor skills - tracing lines on a moving disc. Initially performance was poor but improved. Several days later retested and performed the same as previously even without recollection of doing task before - could form new procedural memories
WMM - Baddely and Hitch (1974)
WMM is a model of STM. It’s concerned with the ‘mental space’ that is active eg working on an arithemtic problem or playing chess or comprehending language etc
WMM - Central Executive (CE)
Allocates subsystems. Supervisory role- monitors incoming data, directs attention and allocates subsystems to tasks. It has a very limited storage capacity.
Coding is modality free = can take any type of coding
WWM - Phonological Loop (PL)
Consist of a phonological store and an articulatory process. PL deals with auditory information and preserves the order in which information arrives. Has a capacity of 2 seconds and is coded acoustically. It is subdivided into-
- phonological store - stores the words you hear
- articulatory process - allows maintenance rehearsal (repeating sounds to keep them in the WM while they are needed)
WMM - Visio-spatial sketchpad (VSS)
Stores visual and/or spatial information when required. Capacity is 3-4 objects and is coded visually. (Eg recalling how many windows your house has).
Logie (1995) subdivided the VSS into -
- visual cache - stores visual data
- inner scribe - records arrangement of objects in visual field
WMM - Episodic Buffer (EB)
Temporary storage of information. Added in 2000. Integrates visual, spatial, and verbal information from other stores. Maintains sense of time sequencing - recording events (episodes) that are happening. Links to LTM.
Coding = modality free
Capacity is limited to about 4 chunks