CHAPTER 8: HUMAN MEMORY• The long and the short of memory• Types of long-term memory• Forgetting• Everyday memory
The Long and the Short of Memory• Short-term memory has been assessed in various ways. • Digit span: People listen to a random series of digits and then try to repeat them back immediately in the correct order. • The maximum number of units (e.g., digits) recalled without error is usually “seven plus or minus two” (Miller, 1956). • Miller (1956) argued that the capacity of short-term memory should be assessed in terms of the number of chunks (integrated pieces or units of information). • Cowan (2000) argued that the capacity of short-term memory is only four chunks.
The Long and the Short of Memory• One major difference is in the length of time for which information is remembered. Much information remains in long-term memory for a lifetime, whereas information in short-term memory is lost rapidly.• Short-term memory capacity is less than the essentially unlimited capacity of long- term memory.
The Long and the Short of Memory• The most convincing evidence that short-term and long-term memory are distinct comes from brain-damaged patients.• The findings from brain-damaged patients provide evidence for a double dissociation (i.e., some patients perform normally on task A but poorly on task B, whereas others perform normally on task B but poorly on task A).• Patients with amnesia have severe problems with long-term memory but have essentially intact short-term memory as assessed by span measures.
Multi-Store Model• Atkinson and Shiffrin (1968): • Sensory stores: • Each of which holds information very briefly and is modality-specific (limited to one sensory modality) • Short-term store: • Of very limited capacity • Long-term store: • Of essentially unlimited capacity and can hold information over extremely long periods of time.
Multi-Store Model• Atkinson and Shiffrin (1968) argued that short- term memory is involved BEFORE long-term memory. • However, an increasingly popular view is that short-term memory is only involved AFTER long-term memory.• Atkinson and Shiffrin assumed that information in short-term memory represents “the contents of consciousness”, implying that ONLY information processed consciously can be stored in long-term memory. • However, there is reasonable evidence for the existence of learning without conscious awareness of what has been learned (implicit learning).
Evaluation• The assumption within the model that there are separate short-term and long-term stores has been influential and is approximately correct.• As we will see, it is a gross oversimplification to argue that there is a single short-term memory store.• It is also a gross oversimplification to argue that there is a single long-term memory store.• It doesn’t make sense to argue that processing in the short-term store occurs before contact has been made with long-term memory.• In contradiction of the assumptions of the multi- store model, learning can probably occur without conscious awareness of what has been learned.
Working Memory• Alan Baddeley and Graham Hitch (1974): • Argued that we use short-term memory much of the time when engaged in the performance of complex tasks. • Used the term working memory to refer to a system combining processing and short-term memory functions.
Working Memory Model• The working memory system is hierarchical.• Central executive: • A modality-free component of limited capacity resembling attention.• Phonological loop: • This holds information briefly in a phonological (i.e., speech based) form.• Visuospatial sketchpad: • This is specialized for spatial and/or visual coding.
Baddeley’s Working Memory SystemThis figure also shows the episodic buffer, which was only added tothe working memory model 25 years after it was first put forward.Figure adapted from Baddeley (2001).
Evidence• Robbins et al. (1996): • Doing the following while playing chess: • Repetitive tapping: this was the control condition. • Random number generation: this involved the central executive. • Pressing keys on a keypad in a clockwise fashion: this used the visuospatial sketchpad. • Rapid repetition of the word “seesaw”: this used the phonological loop. • Results • See next slide.
Effects of secondary tasks on quality of chess-move selection in strongerand weaker players. Adapted from Robbins et al. (1996).
Phonological Loop• According to Baddeley, Gathercole, and Papagno (1998), it is very useful when we are learning new words.• Papagno, Valentine, and Baddeley (1991) found that the learning of foreign vocabulary was greatly slowed down when participants performed another task using the resources of the phonological loop at the same time.• Phonological similarity effect: When a short list of visually presented words has to be recalled immediately in the correct order, recall performance is worse when the words are phonologically similar.
Phonological Loop• According to Baddeley (1986, 1990), the phonological loop has two main components: • Phonological store: directly concerned with speech perception. • Articulatory process linked to speech production.• Supporting evidence comes from studies on brain-damaged patients.
Phonological Loop System Baddeley (1990)
Visuospatial Sketchpad• Temporary storage.• Manipulation of spatial and visual information.• Logie et al. (1989): • Space Fortress: • They found performance on Space Fortress was initially severely impaired when participants also performed a secondary visuospatial task. • However, the adverse effects were greatly reduced after 20 hours of training.
Visuospatial Sketchpad• Klauer and Zhao (2004): • Memory for dot locations and memory for Chinese ideographs. • They found that the spatial interference task disrupted performance more on the spatial main task than on the visual main task. • They also found the visual interference task disrupted performance more on the visual main task than on the spatial main task.
Central Executive• Miyake et al. (2000) and Friedman and Miyake (2004) have provided evidence for three major functions of the central executive: • Inhibition + resistance to distracter interference • Shifting • Updating and monitoring• According to Collette and Van der Linden (2002), the prefrontal cortex is activated during the performance of most central executive tasks, but other areas including parietal cortex are also sometimes activated.
Amnesia• Types of amnesia: • Anterograde amnesia: • A marked impairment in the ability to remember new information learned after the onset of the amnesia. • Retrograde amnesia: • Great difficulty in remembering events from before the onset of amnesia.• Amnesic patients vary in the precise brain areas damaged.
Amnesia can be produced by damage to brain structures in two areas of the brain: a sub-cortical region called the diencephalon, and a cortical region known as the medial temporal lobe.
Explicit vs. Implicit Memory• Edouard Claparède (1873–1940): • Female patient who suffered from amnesia due to chronic alcoholism. • She couldn’t recognize doctors and nurses she saw virtually every day for several years, and she didn’t know what day it was or her own age. • One day, Claparède hid a pin in his hand before shaking hands with this patient. • The following day she was very sensibly reluctant to shake hands with him but felt very embarrassed because she couldn’t explain her reluctance.
Explicit vs. Implicit Memory• The patient had no conscious recollection of what had happened the previous day.• In spite of that, her behavior indicated very clearly that she DID possess some long-term memory of what had happened.• Thus, long-term memory can depend less on conscious recollection than we imagine.• Similar findings have been obtained in much more recent studies on amnesic patients.
Episodic and Semantic Memory• Tulving (1972) distinguished between two long-term memory systems he called: • Episodic memory, which involves conscious recollection of events or episodes from one’s past, generally involving some memory for the relevant time and place. • Semantic memory, which is concerned with our general knowledge. • Episodic and semantic memory are both forms of declarative memory, which is concerned with knowing that something is the case.
Episodic and Semantic Memory• Vargha-Khadem et al. (1997): • Studied two patients (Beth and Jon) who had bilateral hippocampal damage at an early age before they had had the opportunity to develop semantic memories. • Both patients had poor episodic memory for the day’s activities, television programs, and so on. • However, they both attended ordinary schools, and their levels of speech and language development, literacy, and factual knowledge (e.g., vocabulary) were within the normal range. • Thus, they had virtually intact semantic memory.
Episodic and Semantic Memory• Tulving (2002, p. 13) discussed the case of a patient (KC) whose: • “retrograde amnesia is highly asymmetrical: he cannot recollect any personally experienced events..., whereas his semantic knowledge acquired before the critical accident is still reasonably intact. His knowledge of mathematics, history, geography, and other ‘school subjects’, as well as his general knowledge of the world is not greatly different from others’ at his educational level.”
Episodic and Semantic Memory• The opposite pattern was reported by Yasuda, Watanabe, and Ono (1997): • A female amnesic patient had very poor ability to remember public events, cultural, items, historical figures, and some items of vocabulary from the time prior to the onset of the amnesia. However, she was reasonably good at remembering personal experiences from episodic memory dating back to the pre- amnesia period.
Forgetting• Evidence that our memories can be poor for important information comes from the study of passwords. • Brown, Bracken, Zoccoli, and Douglas (2004) found that 31% of their sample of American students admitted to having forgotten one or more passwords.• Most people feel they remember dramatic events (e.g., September 11) in much detail and with great accuracy over long periods of time; these are called flashbulb memories.
“On September 11, did you see the videotape on television of the first plane striking the first tower?”
Forgetting• What did you answer?• Our flashbulb memories are often far less accurate than we imagine.• Pezdek (2003) asked American students the same question.
Forgetting• 73% of the students said “Yes”, which is incorrect (only videotape of the second tower being hit was shown on September 11).• Winningham, Hyman, and Dinnel (2000) found that people’s memories changed considerably in the first few days after hearing about the acquittal of O.J. Simpson, but became consistent after that.• The central issue in forgetting research was identified by the German psychologist Hermann Ebbinghaus (1885/1913). • He carried out extensive studies with himself as the only participant. • This involved learning a list of nonsense syllables having little/no meaning. • He then re-learned the list and assessed forgetting by the savings method (the reduction in the number of trials during re-learning compared to original learning). • Forgetting increased over time (this is known as the forgetting curve).
Hermann Ebbinghaus (1885/1913)
Repression• Sigmund Freud (1856–1939): • Threatening or traumatic memories are often stored in the unconscious and can’t gain access to conscious awareness; this phenomenon is known as repression. • Freud sometimes used the concept of repression to refer merely to the inhibition of the capacity for emotional experience, with traumatic memories being consciously accessed but drained of their emotional significance.• Evidence • Andrews et al. (1999) • Recovered memories from patients. • Lief and Fetkewicz (1995) • Patients who had admitted their “memories” of childhood abuse were false.• Clancy, Schacter, McNally, and Pitman (2000) • Used memory task to produce false memories (see next slide).
Clancy, Schacter, McNally, and Pitman (2000)
Evaluation• There is strong evidence that repressed memories of childhood abuse exist.• Some recovered memories have been shown to be false (e.g., Lief & Fetkewicz, 1995).• Repression theory is very limited, because most forgetting doesn’t relate to traumatic events.
Interference Theory• Hugo Münsterberg (1863–1916)• Proactive interference: • Previous learning interferes with our memory of later learning.• Retroactive interference: • Later learning disrupts memory for earlier learning.
Interference Theory• Isurin and McDonald (2001) argued that retroactive interference explains why people forget some of their first language when acquiring a second language.• Kane and Engle (2000) found that intelligent individuals with high attentional capacity were better able to resist proactive interference than less intelligent ones with low attentional capacity.
Evaluation• Much forgetting inside and outside the laboratory is due to proactive and retroactive interference.• As predicted, the amount of interference (proactive or retroactive) is greatest when the same stimulus is paired with two different responses.• Interference theory tells us little about the internal processes involved in forgetting.• Interference theory accounts for much forgetting, but doesn’t directly explain the precise nature of the forgetting curve.
Cue-Dependent Forgetting• Tulving (e.g., 1979) argued that successful retrieval depends on: (1) The information stored in the memory trace. (2) The information available at the time of retrieval.• People are most likely to remember something when the information available at the time of retrieval matches the information in the memory trace. This is known as the encoding specificity principle.
Encoding Specificity Principle• Tulving (e.g., 1979) • There is information in the memory trace and information is also available on the memory test (e.g., retrieval cue). • The greater the overlap between these two sources of information, the greater the probability that memory will occur. • The information stored in memory would typically include contextual information. • Memory should be better when an individual’s state (e.g., mood state) at the time of testing matches his/her state at the time of learning.
Kenealy (1997): Evidence of State- Dependent Memory
Evaluation• What we remember or forget depends in part on the extent to which information in the memory trace matches that available at the time of retrieval.• There is reasonable evidence for mood-state-dependent memory.• There is evidence (e.g., Muter, 1978) for the surprising prediction that recall can be better than recognition memory.• Retrieval is often more complex than simply comparing the information in the memory trace with that available on the memory test.• Tulving (1979) assumed that context influenced recall and recognition in the same way. In fact, however, it generally influences recall much more than recognition.
Consolidation is the Answer!• The most adequate answer to the question of why the forgetting curve exists is provided by consolidation theory.• According to this theory, consolidation is a long- lasting process fixing information in long-term memory.• The theory’s crucial assumption is that recently formed memories in an early stage of consolidation are especially vulnerable to interference and forgetting.• The initial phase of consolidation lasts for several hours and is centered on the hippocampus.• Support for this theory comes from patients with retrograde amnesia.
Evaluation• Consolidation provides a plausible explanation of why the rate of forgetting decreases over time.• Consolidation theory successfully predicts that retrograde interference effects will be greater shortly after learning has occurred than later on.• Consolidation provides a rather general account, and doesn’t explain why retroactive interference is greatest when two different responses are associated with the same stimulus.• Consolidation theory has little or nothing to say about the mechanisms underlying cue-dependent forgetting.
Everyday Memory• Ecological validity concerns the extent to which laboratory findings generalize (or are applicable) to real life.• Autobiographical memory is the memories we possess, relating to our own past, to the experiences we have had, and to the people who have a special importance to us.• Karney and Frye (2002) found that spouses often recalled their past contentment as lower than their present level of satisfaction.
Everyday Memory• What do elderly people remember? Is it really true that they mostly recall distant childhood memories?• No! • Infantile amnesia: shown by the almost total lack of memories from the first three years of life. • A reminiscence bump: consisting of a surprisingly large number of memories coming from the years of adolescence and early adulthood (especially 15 to 25). • A retention function for memories up to 20 years old, with the older memories being less likely to be recall than more recent ones.
Everyday Memory• According to Conway and Pleydell-Pearce (2000), autobiographical memory depends on an autobiographical memory base and the working self. • The autobiographical memory base contains personal information at three levels of specificity: lifetime periods (e.g., time at secondary school); general events (e.g., a holiday); and event-specific knowledge (e.g., a specific occurrence on a holiday). • The working self is concerned with the self, what it may become in future, and with the individual’s current goals.
Everyday Memory• According to Erikson (e.g., 1968), we go through several psychosocial stages of development: • Childhood: wanting to be nurtured; having fun. • Identity/identity confusion: relating to peers and friends. • Intimacy/isolation: trying to achieve mutual intimacy. • Generativity/stagnation: being concerned/unconcerned about others’ welfare. • Integrity/despair: focus on meaningful/meaningless nature of life.
Evaluation• The notion that autobiographical memory has a hierarchical structure is plausible and in line with the evidence.• There is support for the notion that the self and its goals are important in autobiographical memory.• Our understanding of the role of the working self is based mainly on consciously accessible information. However, some aspects of the working self (e.g., some of its goals) may not be consciously accessible.• As yet, we know little of how the working self interacts with the autobiographical knowledge base to produce recall of specific autobiographical memories.
Eyewitness Testimony• Thousands of people have been put in prison purely on the basis of eyewitness testimony.• Even if the rate of mistaken identification is low, it would still follow that many innocent individuals are in prison unnecessarily.• Eyewitness testimony is often inaccurate because eyewitnesses often do not realize initially that a crime or other event is happening, and so do not attend fully to it.
Eyewitness Testimony• Loftus and Palmer (1974) claimed that eyewitness memories are fragile and can be easily distorted by questioning after the event.• They obtained support for their point of view in a study in which people were shown a film of a multiple-car accident.• After viewing the film, participants described what had happened, and then answered specific questions.
Post-Event Information• Loftus and Palmer (1974) • How fast were the cars going when they hit each other? • How fast were the cars going when they smashed into each other? (a) Hit—average 34 mph. (b) Smashed into— average 41 mph.
Eyewitness Testimony• One week later, all participants were asked, “Did you see any broken glass?”• There wasn’t actually any broken glass in the accident, but 32% of those previously asked about speed using the verb “smashed” said they had seen broken glass.• In contrast, only 14% of those asked using the verb “hit” said they had seen broken glass, and the figure was 12% for the control participants.
Eyewitness Testimony• There has been much research on weapon focus, where the eyewitness attends so closely to the criminal’s weapon that he/she fails to recall details about the criminal and the environment.• Pickel (1999) argued that a weapon may attract attention either because it poses a threat or because it is unexpected in the context in which it is seen. • Man with a gun study.
Other Studies• Kassin et. al. (2001) • Found over 80% of experts in eyewitness testimony agreed that an eyewitness’s confidence is NOT a good predictor of his/her identification accuracy.• Sporer et. al (1995) • Found confident choosers were somewhat more likely than non- confident choosers to make an accurate identification.• Perfect and Hollins (1996) • Found that participants’ confidence didn’t predict the accuracy of their memory for a film about a kidnap.• Heath and Erickson (1998) • There is typically much less memory distortion for central details than for peripheral ones.
Other Studies• Ihlebaek et. al. (2003) • Found inaccuracies and distortions in eyewitness memory obtained under laboratory conditions underestimate eyewitnesses’ memory deficiencies for real-life events.• Valentine, Pickering, and Darling (2003) • Found across 300 real line-ups organized by the London Metropolitan Police that 40% of witnesses identified the suspect, 20% identified a non-suspect, and 40% failed to make an identification.
Eyewitness Testimony• What can be done to improve eyewitnesses’ identification performance? • It has often been argued that warning eyewitnesses that the culprit may not be present in the line-up reduces the changes of mistaken identification. • Line-ups are generally simultaneous, meaning the eyewitness is presented with everyone in the line-up at the same time. • An alternative is to have sequential line-ups in which the eyewitness sees only one person at a time. • However, sequential line-ups also produced a significant reduction in accurate identification rates when the culprit was present. • The eyewitnesses adopt a more stringent criterion for identification with sequential than with simultaneous line- ups.
Evaluation• Important phenomena have been identified (e.g., distorting effects of post-event information; weapon focus effect; poor relationship between eyewitness confidence and accuracy).• Ways of improving the identification performance of eyewitnesses (e.g., warning that the culprit may not be present; sequential rather than simultaneous line-ups) have been discovered.• Post-event information may not distort memory for important information as much as for trivial information (Heath & Erickson, 1998).• Research on eyewitness identification has practical value but has been relatively uninfluenced by theoretical ideas.