Coding, capacity and duration

Outline

Coding- STM= acoustic, LTM= semantic
Capacity- STM= 5-9 items, LTM= unlimited
Duration- STM= 18-30 seconds, LTM= permanent

Discussion

Coding- Baddeley, 1966. Four word lists given: acoustically similar/dissimilar and semantically similar/dissimilar. He found that immediate recall (STM) struggled with acoustically similar, while 20 minutes later (LTM) struggled with semantically similar.
Limitation- artificial stimuli- word lists are meaningless to participants
Capacity- Jacobs,1887. Digit span- recall of digits, increasing each time. Average was 9.3 digits.
Limitation- confounding variables due to era
Miller, 1956. Chunking- can recall 5-9 words just as well as 5-9 letters.
Limitation- contradictory evidence suggests its more likely to be 4 letters/words
Duration- Bahrick, 1975. Showed 17-74 year olds either their yearbooks and asked them to recall as many names as possible, or just asked them to recall freely (no yearbook). Found that with the yearbook, 15 years after graduation was 90% recall, 70% for 48 years after, and without the yearbook, 15 years after was 60% recall, 30% for 48 years after. This suggests LTM duration is very long lasting
Strength- meaningful stimuli- high external validity
Peterson and Peterson, 1959. Participants given consonant syllable and 3-digit number. Asked to count back from 3 digit number, and stopped at retention intervals of 3, 6, 9, 12, 15 or 18. This prevents maintenance rehearsal of the consonant syllable. Recall was worse at 18 seconds.
Limitation- meaningless stimuli, difficult to generalise.

Multi-store model of memory

Outline

Atkinson and Shriffin, 1968
Sensory register- iconic (visual) and echoic (auditory) as well as all other senses. Very large capacity and very short duration (0.5 seconds).
STM- duration= 18- 30 seconds, capacity= 5-9 items, coding= acoustic. Maintenance rehearsal is repetition of material so it remains in the STM.
LTM- duration= permanent, capacity= unlimited, coding= semantic. Prolonged rehearsal in STM leads to info transferring to LTM. Retrieval involves info in the LTM being recalled to STM.

Discussion

Strength- Supporting research for coding, capacity and duration
Limitation- STM may not be unitary store- could be individual stores for visual and auditory info. Studies into amnesia showed that digits read out loud were more difficult to recall than written words to read
Limitation- More than one type of rehearsal- elaborative rehearsal: linking info to current knowledge
Limitation- More than one type of LTM- Tulving: episodic, procedural and semantic
Limitation- Issues with research support: artificial stimuli

Working memory model

Outline

Central executive- limited capacity, coordinates other subsystems and allocates resources
Visuo-spatial sketchpad- limited capacity (3-4 items), records arrangement of objects and stores visual data
Phonological loop- articulatory process: 2 second maintenance rehearsal of words in STM, phonological store: store for the words you hear.
Episodic buffer- limited capacity (4 items). Integrates all information and ensures time sequencing. Links the WM to LTM

Discussion

Strength- patient had trouble processing auditory information but was fine with visual information, suggesting damage to the phonological loop- separate from visuo-spatial sketchpad. However, this evidence is difficult to generalise as it deals with unique cases, often involving trauma
Strength- Dual task performance, Baddeley. Found that people found it harder to simultaneously do two task in the same store (e.g. two visual tasks) than two mismatched tasks (e.g. auditory task and visual task). Suggests there must be two separate subsystems for auditory and visual information.
Limitation- lack of clarity over central executive- may be separate components
Strength- word length effect: list of long words more difficult to remember. Supports 2 second capacity of articulatory process
Strength- brain scan studies: high levels of activity in left pre-frontal cortex during activities which stimulate the CE

Types of LTM

Outline

Tulving, 1985
Episodic- recall of events (episodes), time stamped, requires conscious recall, includes people, places and objects
Semantic- knowledge of the world/facts, not time stamped, require conscious recall
Procedural- how to do things, not time stamped, unconscious recall

Discussion

Strength- clinical evidence e.g. Clive Wearing. Forgot events (e.g. wedding) but remembered facts and how to play piano. Damaged episodic memory, but intact semantic and procedural. Suggests there are multiple stores for LTM
Strength- Neuroimaging evidence: Tulving found that for episodic memories, the right pre-frontal cortex was active, while the left pre-frontal cortex was active for semantic memories
Strength- real life application: can be used to improve episodic memory for old people
Limitation- may only be two stores: declarative (episodic and semantic) and non-declarative (procedural). Declarative requires conscious recall, while non-declarative does not.

Interference

Outline

When one piece of information blocks another, causing distortion or forgetting
Proactive- old interferes with new e.g. teacher can't remember new class' names because she keeps remembering last year's class' names
Retroactive- new interferes with old e.g. teacher can't remember last year's class' names because she remembers the new class' names
Effects of similarity- more similar= more interference
McGeoch and McDonald, 1931. Gave 6 groups of participants the same word list to remember. They then gave each group a different word list, each list different for each group. This included synonyms, antonyms, nonsense syllables, 3-digit numbers, no new list and unrelated words. They then asked them to recall the first word list and found those who had synonyms had worse recall while those with no new list had best recall

Discussion

Strength- lab studies: good validity and control over extraneous variables
Limitation- lab studies- too artificial: word lists are meaningless, and therefore results can't be generalised to everyday life
Strength- real life studies: Baddeley, 1977. Rugby players had to recall all of the matches they'd played that season. It didn't matter if their last match was 3 weeks ago, interference depended on the number of matches since. The best recall was if they hadn't played since that match
Limitation- time between learning: in real life, time between learning and recall is often quite long, while in lab studies it is very short for practicality

Retrieval failure

Outline

Tulving,1983. Encoding Specificity Principle (ESP) states that the cue must be present at both encoding and recall
Context-dependent forgetting- external cues. Godden and Baddeley, 1975. Studied deep sea divers and their recall of a word list. They would learn the list either on land or in the sea, and then recall it either on land or in the sea. There were 4 conditions of learning---recalling: 1. OL--OL 2. OL---IS 3. IS---OL 4. IS---IS. The best recall was when the location matched (OL---OL or IS---IS). When conditions didn't match, accuracy was 40% worse.
State-dependent forgetting- internal cues. Carter and Cassaday, 1998. Studied the effects of antihistamines, which cause drowsiness, on learning and recall. There were 4 conditions of learning---recalling: (D= drug, ND= no drug) 1. D---D 2. D---ND 3. ND---ND 4. ND---D. The best recall was when the state matched (D---D or ND---ND)

Discussion

Strength- supporting evidence (Godden and Baddeley, Carter and Cassaday). Increased validity
Limitation- Context effects not strong: context has to be very different for any significant effect
Limitation- may only affect recall, not recognition: Godden and Baddeley replicated their study, but the divers had to say if they recognise the word read to them, and performance was the same in all 4 conditions
Limitation- ESP can't be tested as it's based on assumptions: circular arguments aren't scientific
Strength- Real life application: going upstairs then forgetting why, then going back downstairs only to remember again

Factors affecting EWT- misleading information

Outline

Leading questions- Loftus and Palmer, 1974. Asked participants to watch a video of a car crash and then asked them questions after. One question was 'How fast were the cars going when they _________ into each other?' In the space was a different verb: 'smashed', 'hit', 'bumped', 'contacted' and 'collided'. When 'smashed' was used, the participants' average speed guess was 40.5mph, but with 'contacted' the average speed guess was 31.8mph
Response bias explanation- wording doesn't change memory, just changes how participants choose to respond
Substitution explanation- wording changes memory- participants who heard 'smashed' were more likely to report broken glass even though there wasn't any
Post event discussion- Gabbert, 2003. Participants all watched a video of the same crime, but each video was from a different perspective for each participant. These different perspectives meant some participants could see things that other participants couldn't. They then had a post event discussion. In one case, one participant told another the title of a book being carried that the other participant wasn't able to see in their video. 71% of participants reported things they had not actually seen. In a control group with no PED, 0% of participants reported anything they hadn't actually seen.

Discussion

Strength- real life application: useful for the legal system to ensure accuracy in EWTs
Limitation- artificial tasks: the video clips were not real crimes, but if they were, the participants' reaction may have been different
Limitation- individual differences: elderly people are usually less accurate in EWTs
Limitation- demand characteristics: want to be helpful for the researcher

Factors affecting EWT- anxiety

Outline

Positive effect- Yuille and Cutshall, 1986. Fight or flight response increases alertness. Studied a real life shooting in a gun shop in which the owner shot and killed a thief. They interviewed the witnesses 5 months later and determined accuracy based on how many details they could recall, rated their stress level and if they had any subsequent emotional problems. The witnesses who reported the highest level of stress were more accurate (88%) than those who reported lowest levels of stress (75%).
Negative effect- Johnson and Scott, 1976. Anxiety creates physiological arousal so concentration is worse. Participants believed they were doing a lab study but when in the waiting room, they experienced either a high anxiety condition or low anxiety condition. In the high anxiety condition, there was an argument heard, as well as broken glass, and a man exited with a bloodied knife. In the low anxiety condition, the same argument was heard, without broken glass, and the man exited with a pen and grease. They were then asked to recognise the suspect out of a group of photos. For the low anxiety condition, recall was 49%, while it was 33% for the high anxiety condition.
Explanation for contradictory evidence- Yerkes and Dodson, 1908. Said relationship between emotional arousal and performance is an inverted U. Deffenbacher, 1983. Said that too low levels of anxiety lead to low recall, and too high level of anxiety lead to low recall. Hence, their is an optimal level of anxiety for best recall.

Discussion

Limitation- weapon focus effect may be due to unusualness, not anxiety. Pickel, 1998. Asked participants to watch a clip of a theft. The thief was either carrying a gun, raw chicken, a wallet or scissors. Recall was worse for the gun and chicken
Limitation- field studies lack control: post event discussion, role of media
Limitation- ethical issues: psychological harm, deception
Limitation- inverted U is too simplistic: doesn't take into account cognitive, emotional and behavioural anxiety, just physical.
Limitation- demand characteristics: work out aim and act accordingly

Cognitive interviews

Outline

Geiselmann and Fisher, 1992.
Report everything- trivial elements may actually be important or could trigger other memories
Reinstate the context- go back to crime scene in your head and focus on weather, emotional state etc.
Reverse the order- change the chronology to avoid basing on expectations or lying
Change the perspective- disrupts expectations
Enhanced cognitive interview- Fisher, 1987.When to have eye contact, reduce distractions and anxiety, asking open-ended questions

Discussion

Limitation- time consuming and expensive
Strength- some elements more helpful than others e.g. report everything
Strength- supporting evidence for ECI: provides more correct information than standard interviews
Limitation- increase in inaccurate information as well: 61% increase in inaccurate information compared to standard interviews