Chapter 7. Human Memory. Human Memory: Basic Questions. How does information get into memory? How is information maintained in memory? How is information pulled back out of memory?.
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Human Memory: Basic Questions
Fig 7.2 – Three key processes in memory.Memory depends on three sequential processes: encoding, storage, and retrieval. Some theorists have drawn an analogy between these processes and elements of information processing by computers, as depicted here. The analogies for encoding and retrieval work pretty well, but the storage analogy is somewhat misleading. When information is stored on a hard drive, it remains unchanged indefinitely and you can retrieve an exact copy. As you will learn in this chapter, memory storage is a much more dynamic process. Our memories change over time and are rough
reconstructions rather than exact copies of past events.
Encoding: Getting Information Into Memory
Fig 7.3 – Models of selective attention.Early-selection models propose that input is filtered before meaning is processed. Late-selection models hold that filtering occurs after the processing of meaning. There is evidence to support early, late, and intermediate selection, suggesting that the location of the attentional filter may not be fixed.
Levels of Processing: Craik and Lockhart (1972)
Fig 7.4 – Levels-of-processing theory.According to Craik and Lockhart (1972), structural, phonemic, and semantic encoding—which can be elicited by questions such as those shown on the right— involve progressively deeper levels of processing, which should result in more durable memories.
Fig 7.5 – Retention at three levels of processing.In accordance with levels-of-processing theory, Craik and Tulving (1975) found that structural, phonemic, and semantic encoding led to progressively better retention.
Enriching Encoding: Improving Memory
Storage: Maintaining Information in Memory
Fig 7.8 – The Atkinson and Shiffrin model of memory storage.Atkinson and Shiffrin (1971) proposed that memory is made up of three information stores. Sensory memory can hold information just long enough (a fraction of a second) for a small portion of it to be selected for longer storage. Short-term memory has a limited capacity, and unless aided by rehearsal, its storage duration is brief. Long-term memory can store an apparently unlimited amount of information for indeterminate periods.
Fig 7.9 – Sperling’s (1960) study of sensory memory.After the subjects had fixated on the cross, the letters were flashed on the screen just long enough to create a visual afterimage. High, medium, and low tones signaled which row of letters to report. Because subjects had to rely on the afterimage to report the letters, Sperling was able to measure how
rapidly the afterimage disappeared by varying the delay between the display
and the signal to report.
Short Term Memory (STM)
Fig 7.10 – Peterson and Peterson’s (1959) study of short-term memory.After a warning light was flashed, the subjects were given three consonants to remember. The researchers prevented rehearsal by giving the subjects a three-digit number at the same time and telling them to count backward by three from that number until given the signal to recall the letters. By varying the amount of time between stimulus presentation and recall, Peterson and Peterson were able to measure how quickly information is lost from short-term
Short-Term Memory as “Working Memory”
Fig 7.11 – Short-term memory as working memory.This diagram depicts the revised model of the short-term store proposed by Alan Baddeley (1986), who views STM as a mental scratchpad or temporary workspace. According to Baddeley, working memory includes three components: a phonological rehearsal loop, a visuospatial sketchpad, and an executive control system.
Long-Term Memory: Unlimited Capacity
How is Knowledge Represented and Organized in Memory?
Retrieval: Getting Information Out of Memory
Forgetting: When Memory Lapses
Fig 7.18 – Ebbinghaus’s forgetting curve for nonsense syllables.From his experiments on himself, Ebbinghaus concluded that forgetting is extremely rapid immediately after the original learning and then levels off. However, subsequent research has suggested that this forgetting curve is unusually steep. (Data from Ebbinghaus, 1885)
Fig 7.19 – Recognition versus recall in the measurement of retention.Luh (1922) had subjects memorize lists of nonsense syllables and then measured their retention with either a recognition test or a recall test at various intervals up to two days. As you can see, the forgetting curve for the recall test was quite steep, whereas the recognition test yielded much higher estimates of subjects’ retention.
Why Do We Forget?
Fig 7.21 – Retroactive and proactive interference.Retroactive interference occurs when learning produces a “backward” effect, reducing recall of previously learned material. Proactive interference occurs when learning produces a “forward” effect, reducing recall of subsequently learned material. For example, if you were to prepare for an economics test and then study psychology, the interference from the psychology study would be retroactive interference. However, if you studied psychology first and then economics, the interference from the psychology study would be proactive interference
Fig 7.22 – Estimates of the prevalence of childhood physical and sexual abuse.In one of the better efforts to estimate the prevalence of child abuse, MacMillan and her colleagues (1997) questioned a random sample of almost 10,000 adults living in the province of Ontario, Canada, about whether they had been abused during childhood. As you can see, males were more likely to have experienced physical abuse and females were more likely to have suffered sexual abuse. Moreover, the data support the assertion that millions of people have been victimized by childhood sexual abuse, which is far from rare. (Based on
data from MacMillan et al., 1997)
Fig 7.24 – The prevalence of false memories observed by Roediger and McDermott (1995). The graph shown here summarizes the recognition test results in Study 1 conducted by Roediger and McDermott (1995). Participants correctly identified words that had been on the lists that they had studied 86% of the time and only misidentifed unrelated words that had not been on the lists 2% of the time, indicating that they were paying careful attention to the task. Nonetheless, they mistakenly reported that they “remembered” related target words that were not on the lists 84% of the time—a remarkably high prevalence of false memories. (Data from Roediger & McDermott, 1995)
The Physiology of Memory
Fig 7.25 – The anatomy of memory.All the brain structures identified here have been implicated in efforts to discover the anatomical structures involved in memory. Although its exact contribution to memory remains the subject of considerable debate,
the hippocampus is thought to play an especially central role in memory.
Fig 7.26 – Retrograde versus anterograde amnesia.In retrograde amnesia, memory for events that occurred prior to the onset of amnesia is lost. In anterograde amnesia, memory for events that occur subsequent to the onset of amnesia suffers.
Are There Multiple Memory Systems?
Fig 7.27 – Theories of independent memory systems.There is some evidence that different types of information are stored in separate memory systems, which may have distinct physiological bases. The diagram shown here, which blends the ideas of several theorists, is an adaptation of Larry Squire’s (1987) scheme. Note that implicit and explicit memory are not memory systems. They are observed behavioral phenomena that appear to be handled by different hypothetical memory systems (the procedural and declarative
memory systems), which cannot be observed directly.
Improving Everyday Memory