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Chapter Summary
This chapter introduces the topic of memory systems. Some memory researchers suggest that there are five memory systems (working memory, episodic memory, semantic memory, procedural memory and the perceptual representation system). William James is credited with making the first distinction between memory systems when he distinguished between primary and secondary memory. Atkinson and Shiffrin’s (1968) influential modal model of memory proposed three memory systems (sensory memory, short-term memory, and long-term memory).
Sensory memory receives stimuli from our sensory systems and it is proposed that there is a sensory memory system for each of our six senses: the visual form is known as iconic memory, and the auditory form is known as echoic memory. These forms of sensory memory hold information for a brief period of time. Short-term memory receives information from both sensory memory and long-term memory. Information in short-term memory is retained for about 18 seconds and George Miller proposed that the capacity of short-term memory was around five to nine items. The capacity of short-term memory can be increased through chunking, in which you can group pieces of information together in a meaningful way. As a result of shortcomings of such conceptualization, short-term memory was reconceptualised by Baddeley and Hitch (1974) as working memory.
Working memory refers to the performance of complex cognitive tasks based on readily accessible information. Baddeley, who proposed this system, describes several interrelated components including memory storage subsystems like the phonological loop, visuo-spatial sketchpad, and the episodic buffer, as well as the attentionally based control system known as the central executive. The central executive and these subsystems are said to be fluid systems, whereas visual semantics, episodic long-term memory, and language are crystallized systems.
Long-term memory can be divided into declarative (or explicit) and non-declarative (or implicit) memory. Tulving further distinguished between episodic memory (memory system concerned with personally experienced events) and semantic memory (memory system concerned with knowledge of words, concepts, and their relationships) in explicit (or declarative) long-term memory. This view of separate memories was supported by experiments on amnesic patients, such as WJ, whose brain injury severely disrupted her episodic memory but spared her semantic memory. Rather than showing a recency bias (tendency to recall events from recent past) in recalling events, WJ demonstrated a primacy bias (tendency to recall events from relatively distant past). NN was another amnesic patient who also demonstrated the dissociation between memory systems, showing deficits in episodic memory but not semantic memory. Semantic memory, on the other hand, refers to memory for facts and general knowledge. For example, knowing that the capital on Canada is Ot-tawa would be a semantic memory. When you can’t come quite come up with the memory, but feel as if you know it, you are experiencing the tip-of-the-tongue phenomenon. The notion of spreading activation also emerged from the study of semantic memory. Spreading activation proposes that activation spreads along pathways in semantic memory as semantic memory is searched. The activation spreads from node to node along these pathways.
Tulving also differentiated between remembering and knowing, explaining that people can know something without exactly remembering the related event (butcher-on-the-bus-phenomenon). This distinction led to the emergence of implicit memory, which is memory with-out any episodic awareness. Amongst many approaches, the method of opposition has been used to study implicit memory. The findings from experiments on implicit memory have supported the idea of a fifth memory system, the perceptual representation system, which is thought to be ac-countable for priming effects. Priming is an unconscious process that results in a response to a target after a previous exposure to a prime (a stimulus presented prior to the target). When there is a relation between the prime and target the response to the target is facilitated such that they respond faster. Priming effects are commonly tested in a lexical decision task (LDT) in which participants have to decide if a string of letters presented as the target is a word or not. Spreading activation has also shed light on how priming works. Involuntary semantic memories, or mind popping as Kvavilashvili and Mandler called it, are an example of priming.
Since Tulving’s distinction between semantic and episodic memory, there have been other memory systems proposed. For example, procedural memory refers to skilled performances, like riding a bicycle, that rely on tacit knowledge (versus explicit knowledge).
According to the connectionist model, in order for previous events to be recalled, some connections need to be inhibited while others need to be excited. With age, this becomes more difficult. Naveh-Benjamin, for example, came up with the associative deficit hypothesis to account for the trouble elderly people have in recalling names and faces. Another problem with memory that is not associated with age but rather with alcoholism is Korsakoff’s syndrome, a form of amnesia. Patients suffering from it are said to have a disconnection syndrome. Of course, Alzheimer’s disease also has strong implications for memory. With such a disease, as well as with aging, remembering to do things at a future time (prospective memory) becomes difficult and in some cases nearly impossible. Errorless learning, however, has been shown to make the most out of patients’ intact memory. For amnesic patients, it is the act of learning new skills that helps them (method of vanishing cues).
Chapter Objectives
- To distinguish between various memory systems.
- To explore sensory and short-term memory.
- To distinguish between short-term and working memory
- To outline Tulving’s approach to memory.
- To look at various models of semantic memory.
- To review experimental evidence for the role of spreading activation in semantic memory.
- To examine the concept of working memory.
- To identify what the study of older individuals and people with memory deficits tells us about the nature of memory.