Memory

Memory

1. Short Term Memory

   • Capacity
     • Baddeley et al (1975)
     • Aim
       • To see if people could remember more short words than long words in a series recall test, and so demonstrate that pronunciation time, rather than the number of items to be recalled, determines the capacity of short-term memory
     • Procedure
       • The reading speed of the participants was measured
       • Participants were then presented with sets of five words of a screen
       • The words were taken from one of two sets: a set of one-syllable words (e.g. harm, wit, sum) or a set of polysyllabic words (e.g. opportunity, aluminium, university)
       • The participants were asked to write down the five words in serial order immediately after presentation. They recalled several lists of both short and long words
     • Findings
       • Participants could recall considerably more short words than long words
       • They were able to recall as many words as they were able to articulate in about 2 seconds
       • There was a strong positive correlation between reading speed and memory span
     • Conclusion
       • Immediate memory span represents the number of items of whatever length that can be articulated in approximately 2 seconds
     • Evaluation
       • It might simply be that short words are easier to recall than longs words because they are more familiar to us
       • Baddeley et al responded to this criticism in later versions of the study and clearly the importance of pronunciation time over familiarity
       • Miller had not been able to account for the findings of research which showed that immediate memory span depends on the nature of the stimulus, i.e. the kind of words and the language in which they are spoken. This study can explain such findings
     • Simon (1974)
       • Argues that it depended on the size of the chunks
         • Small chunks = more capacity; larger chunks = smaller capacity
     • Jacobs (1887) and Miller (1957)
       • The Magical Number Seven
       • 7 +/- 2 (5, 7 or 9)
       • Miller believed it was the number of chunks of information that was important
   • Duration
     • Aim
       • To test how long STM lasts when rehearsal is prevented
     • Procedure
       • Participants were briefly shown a consonant trigram (i.e. three letters such as CPB or NGV)
       • Participants were asked to count backwards in threes from a specified number to stop them rehearsing the letters
       • After intervals of 3, 6, 9, 12, 15 or 18 seconds, participants were asked to recall the original trigram
       • The procedure was repeated several times using different trigrams
     • Findings
       • Participants were able to recall over 80% of trigrams after a 3-second interval
       • Progressively fewer trigrams were recalled as the time intervals lengthened
       • After 18 seconds, fewer than 10% of the trigrams were recalled correctly
     • Conclusion
       • The larger the recall interval, the lower the percentage of trigrams correctly recalled
     • Evaluation
       • Trigrams are rather artificial things to remember and may not reflect everyday memory
       • It is possible, however, that interference from the earlier trigrams (not merely decay) caused the poor recall
       • Not that the experimental method used in this study allows us to see the (causal) effect of time passing (independent variable) or recall (dependent variable)
     • Peterson and Peterson (1959)
   • Encoding
     • Baddeley (1966)
     • Aim
       • To explore the effects of acoustic and semantic encoding in STM
     • Procedure
       • Participants were divided into four groups. Each group heard a list of five words drawn from one of the following categories
         • Acoustically similar words (e.g. man, mad, map)
         • Acoustically dissimilar words (e.g. pen, day, few)
         • Semantically similar words (e.g. great, big, large)
         • Semantically dissimilar words (e.g. hot, old, late)
     • Findings
       • Acoustically similar words were much harder to recall in the correct order (only 55% accuracy) than words with dissimilar sounds (about 75% accuracy)
       • Similarity of meaning had only a very slight detrimental effect
       • The effects of sound similarity disappeared when he tested participants' long-term learning. This suggests that a major factor affecting encoding is whether the items are being stored in STM or LTM
     • Conclusion
       • These findings support those of Conrad
         • STM relies more on the sound of the words rather than on their meaning, as shown by the difficulty participants had in recalling the correct order of words that sounded similar
     • Evaluation
       • The use of the experimental method allows a causal link to be drawn between type of coding used in STM and the accuracy of recall
       • However, the conclusion of this study might not reflect the complexity of encoding. Evidence from other studies has shown that, in certain circumstances, STM may use other forms of encoding
     • Types
       • Acoustic: the sound of the stimulus
       • Visual: the physical appearance of the stimulus
       • Semantic: the meaning of the stimulus

2. Models

   • Multi-Store Model
     • Atkinson and Shiffrin (1968)
       • Created the information-processing system to help explain how memory works
     • Evidence for a Distinction Between STM & LTM
       • Glanzer and Cuntiz (1966)
         • When participants were distracted they lost the recency effect but not the primary effect
         • LTM: The Primary Effect (beginning of the word list)
         • STM: Recency Effect (the end of a word list)
   • The Working Memory Model
     • Baddeley and Hitch focus on short-term memory as an active process with different components
     • Components
       • The Central Executive (CE)
         • Is the control centre responsible for coordinating the other slave units
         • Processes information from any of the senses
         • Minimal storage capacity
         • If we are attempting to do two things at the same time, it is the CE that switches our attention between the two, deciding which other components of the working memory to use
         • Evidence
           • Imbo et al (2007)
           • Participants were given long multiplication tasks to do in their head. The carry over requires the articulatory loop, and the calculation requires the CE (and presumable LTM). More complex sums involving larger numbers and more 'carry overs' made the task more difficult, suggesting that the CE is involved in both holding the carry overs and storing its value
       • Slave Systems
         • Articulatory (Phonological) Loop
           • Is sometimes called the inner voice
           • Holds sounds for a few moments (one to two seconds), storing the sound temporarily
           • Baddeley et al found that the loop can hold about 2 seconds worth of sounds, so it can hold more short words than it can long ones
           • Evidence
             • This store appears to hold the number of words you can say in two seconds
             • Able to rehearse and recall more short words
             • However, if participants are given an articulartory suppression task, neither short words nor long words can be rehearsed and both tasks suffer
         • Visuo-Spatial Scratch Pad
           • Inner eye
           • Limited capacity
           • Stores visual information in its component form
           • It also considers spatial arrangement of shapes
           • Evidence suggests that we use the scratch pad to manipulate images in our head
           • Evidence
             • Tasks were provided that involved doing two simultaneous visual tasks
             • Performance on both visual tasks suffers when done together because the capacity of the sketchpad is limited. Baddeley himself reported an incident when he was listening to a game of American football whilst driving
         • Episodic Buffer
           • Added by Baddeley in 2000
           • The CE has no storage of its own
           • Baddeley realised that there needed to be a store that could hold and coordinate information from all three other stores as well as from LTM
     • Research Evidence
       • Baddeley (1986)
       • Participants were asked to complete two tasks simultaneously
         • To remember a list of numbers (a so called digit span task)
         • To answer true of false to a number of problems
       • If STM is a unitary (single store) as proposed by the multi-store model, and has a capacity of around 7, then as task 1 reached 7 digits there would be no capacity left to carry out task 2
     • Evaluation
       • Active Process
         • It sees memory as an active process and not merely a passive store. Keeping in with modern views of memory that don't see it as a 'thing' but a function or process
       • Rehearsal
         • Rehearsal is important in the phonological loop. Widely considered that the multi-store model does place too great an emphasis on rehearsal in transferring information to STM
       • PET Scans (Positron Emission Tomography
         • Show that different parts of the brain are active when different parts of the system are in use. Further evidence for distinct components. The CE seems to reside in the frontal cortex and the scratch pad in the right side of the occipital lobe, associated with vision
       • Amnesiac Case Studies
         • Shallice and Warrington
           • A single component STM is unable to explain the case of KF, who, following a motorbike accident, suffered impairment of his STM. Although his memory for verbal material was poor his memory for visual information was unaffected
             • Can be explained by damage to the articulartory loop but with the sketchpad remaining intact
         • Baddeley (1986)
           • Found that patients with damage to their frontal lobe had problems concentrating, suggesting damage to the CE. The fact that different brain areas appear responsible for separate functions, therefore separate components does support the concept of a multi-component system
       • However, there are still issues...
         • Very little is known about the CE. No idea of its capacity. Some see it as an umbrella store doing all the functions that can't be explained by the slave units - not a unitary component rather a collection of independent by interacting entities

3. Eye-Witness Testimony

   • How accurately we recall details of events witnessed
   • Elizabeth Loftus
     • Experiment 1
       • After watching the car crash, participants were asked how fast the car was going
       • Some questionnaires said how fast was the car going when it hit the other car, others used the word smashed or contacted instead of hit
     • Experiment 2
       • Students were shown a video of a multiple car crash. One week later they were brought back and asked was there any broken glass, again using the various verbs; hit, smashed, or contacted
     • The more violent the verb used, the higher the estimated speed and the more likely to say there was broken glass
     • Evaluation
       • Methodology & Ethics
         • Laboratory experiments are high in reliability
         • Although films of real events were shown participants would have experienced things differently if they had been present at the car crash
           • Lack of ecological validity
         • Ethics - Participants were deceived therefore debriefing would be necessary afterwards
       • Demand Characteristics
         • Participants might have guessed the aim of the experiment and changed their behaviour
         • To reduce demand characteristics, Loftus offered money to participants who got the recall correct
         • Despite this incentive over 70% still got the recall details wrong
   • Real-Life EWT
     • Yuill and Cutshall (1986)
       • Provided evidence for the accuracy of testimony regarded real-life events. They interviewed 13 witnesses to a real-life shooting involving the owner of the store and an armed thief. The storeowner was wounded but recovered. The thief was shot dead. Some witnesses had seen the incident close to, while others were more distant. The interviews showed that:
         • Witnesses gave impressively accurate accounts several months later
         • Those closest to the event provided the most detail
         • Misleading questions had no effect on accuracy
         • Those who had been most distressed at the time of the shooting proved the most accurate 5 months later
   • Factors Affecting EWT
     • Blatantly Wrong Information
       • Has no effect on memory
       • Loftus showed participants a set of sliders with the theft of a large red handbag, and were then asked to read out accounts of the incident. Some contained errors (e.g. colors)
         • Resisted blatantly wrong information
       • Memory for events can be fundamentally altered in the light of misleading post-event info.
       • Artificial events = low ecological validity, normally in a law court (tension) - difficult to reproduce such conditions - real events more memorable
     • Schemas
       • Leads to distortions in memory due to stereotyping a situation
       • Brewer and Treynes studied effect on visual memory. Designed a fake office room. Contained related (e.g. computer, mouse) and bizarre items (skulls). Couldn't remember bizarre items, and made up other items that weren't there (e.g. pens)
       • Vague concept, unrealistic
     • Weapon Focus
       • Those in the threatening situation were unable to recall details about the scientists appearance, due to having a narrow focus on the knife and blood
       • Loftus - participants were presented with two different situations, one familiar and one different
         • Two scientists having a conversation about equipment failure. Man walked out with grease on his hands and holding a pen
         • Heated discussion, chairs breaking. Man walks out with a bloody paper knife and covered in blood
         • Results were supported by a similar study by Loftus and Burns involving videos. Laboratory study lacks validity. Ethical issue of possible trauma with someone covered in blood
     • Real-Life EWT
       • It improves the accuracy of EWT
       • Yuill and Cutshall's study
         • It is high in validity because it was a real life situation. It is low in ecological validity because it is only one example of real-life EWT
     • Anxiety
       • The fear narrows the focus of attention and gives rise to very accurate recall of the central details at the scene, but less accurate recall of the peripheral details
       • Loftus, lab study, exposed to one situation. 1) overheard a discussion in a lab about an equipment failure. A person then emerged from the lab holding a pen with grease in his hair. 2) Overheard a heated and hostile extreme, between people and the lab. Sound of breaking glass and smashing chairs, man emerges with a knife and covered in blood
       • Lacks validity, different images emerge compared to real life field studies. Ethical issues - deception, psychological harm
   • The Effects of Age
     • Young People & EWT
       • Poole and Lindsay (2001)
         • Got children of varying ages (3-8) to watch a science demonstration following which they listened to a story which contained some of the science material but also some new information. Later when they were questioned about the science demonstration it was found that they threw in some of the story as well. In a follow up they were asked to consider where they had got the information from (the demonstration or the story)
           • The older children could mostly do this successfully but the ones in the younger age group were less able to distinguish the source of the information. Poole and Lindsay therefore concluded that since young children are poor at 'source recognition' they are unlikely to make for good eye witnesses
       • Flin et al (1992)
         • Staged an incident and questioned children and adults about it a day later and again 5 months later. Both groups (young and old) performed equally well the following day but after 5 months the children's group had forgotten significantly more suggesting that EWT of children becomes less reliable over time
       • Gordon et al (2001)
         • Believed that children can make good witnesses but that they're particularly prone to suggestion. Relating to leading questions: children could be especially susceptible
     • Old People & EWT
       • Memon et al (2003)
         • Reworked the Flin et al study with two older age groups (6-33 and 60-82). When questioned 35 minutes after an event age had little effect on accuracy of recall, however, a week later the older age group had declined significantly in their accuracy
       • Yarmey (1993)
         • Found little difference in accuracy of age-related recall but a difference in confidence of recall. She got a young woman to stop people in the street and chat to them for 15 seconds. She did this with 651 participants of varying age. Two minutes later the participants were stopped again and asked to recall the physical characteristics of the woman. All age groups performed similarly but younger age groups were significantly more confident in their recall
     • Methodological Issues
       • There is an idea that improved recall is due to them recognising people from their own age group
         • Anastasi and Rhodes (2006)
           • Tested 3 age groups (teenage/20s, 30s/40s, and 50s-70s). Each participant was shown 24 photographs of a mixture of age groups. Later they were shown 48 photographs (24 same as before and 24 different photos). The participants had to say which ones they'd been shown earlier
             • It was found that generally the young and middle-age groups were better at recall, however all three groups were better at recognising photographs of their own age group
         • A similar rule also applies to race. We are better at recognising people from our own ethnic group than from others
     • Own-Age Bias
   • Anxiety
     • High levels of anxiety can have a negative impact on recall
       • In a meta-analysis of studies Deffenbacher et al found that heightened emotion had led to less accurate recall by witnesses
         • Evaluation: some studies may have had a bad method, or the results could not have a good relationship. Focuses on quantity rather than quality
     • High levels of anxiety can improve recall
       • Christianson and Hubinette questioned 110 witnesses to 22 real bank robberies and found that those who had been threatened during the raids had a more accurate recall of events
     • The Inverted U Relationship or Yerkes-Dodson Law
       • This relationship states that stress or anxiety increases performance up to an optimal point. After that, further increases in anxiety lead to a falling off of performance. This also seems to apply to the relationship between anxiety and recall. In the studies mentioned above it seems reasonable to assume that research showing improving performance were describing patterns to the left of the graph and those showing impairment were describing patterns to the right