theories of memory -- 6/1/23
Today's selection -- from This Is Your Brain On Music by Daniel J. Levitin. Is memory relational or absolute?
"The big debate among memory theorists over the last hundred years has been about whether human and animal is relational or absolute. The relational school argues that our memory system stores information about the relations between objects and ideas, but not necessarily details about the objects themselves. This is also called the constructivist view, because it implies that, lacking sensory specifics, we construct a memory representation of reality out of these relations (with many details filled in or reconstructed on the spot). The constructivists believe that the function of memory is to ignore irrelevant details, while preserving the gist. The competing theory is called the record-keeping theory. Supporters of this view argue that memory is like a tape recorder or digital video camera, preserving all or most of our experiences accurately, and with near perfect fidelity.
"Music plays a role in this debate because -- as the Gestalt psychologists noted over one hundred years ago -- melodies are defined by pitch relations (a constructivist view) and yet, they are composed of precise pitches (a record-keeping view, but only if those pitches are encoded in memory).
"A great deal of evidence has accumulated in support of both viewpoints. The evidence for the constructivists comes from studies in which people listen to speech (auditory memory) or are asked to read text (visual memory) and then report what they've heard or read. In study after study, people are not very good at re-creating a word-for-word account. They remember general content, but not specific wording.
"Several other studies also point to the imperfection of memory. Seemingly minor interventions can powerfully affect the accuracy of memory retrieval. An important series of studies was carried out by Elizabeth Loftus of the University of Washington, who was interested in the accuracy of witnesses' courtroom testimonies. Subjects were shown videotapes and asked leading questions about the content. If shown two cars that barely scraped each other, one group of subjects might be asked, 'How fast were the cars going when they scraped each other?' and another group would be asked, 'How fast were the cars going when they smashed each other?' Such one-word substitutions caused dramatic differences in the eyewitnesses' estimates of the speeds of the two vehicles. Then Loftus brought the subjects back, sometimes up to a week later, and asked, 'How much broken glass did you see?' (There really was no broken glass.) The subjects who were asked the question with the word smashed in it were more likely to report 'remembering' broken glass in the video. Their memory of what they actually saw had been reconstructed on the basis of a simple question the experimenter had asked a week earlier.
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"Findings like these have led researchers to conclude that memory is not particularly accurate, and that it is constructed out of disparate pieces that may themselves not be accurate. Memory retrieval (and perhaps storage) undergoes a process similar to perceptual completion or filling in. Have you ever tried to tell someone about a dream you had over breakfast the next morning? Typically our memory of the dream appears to us in imagistic fragments, and the transitions between elements are not always clear. As we tell the dream, we notice gaps, and we almost can't help but fill them in as we unfold the narrative. 'I was standing on top of a ladder outside listening to a Sibelius concert, and the sky was raining Pez candy ... ' you might begin. But the next image is of yourself halfway down the ladder. We naturally and automatically fill in this missing information when retelling the dream. 'And I decided to protect myself from this Pez pelting, so I started climbing down the ladder where I knew there was shelter .... '
"This is the left brain talking (and probably the region called orbitofrontal cortex, just behind your left temple). When we fabricate a story, it is almost always the left brain doing the fabricating. The left brain makes up stories based on the limited information it gets. Usually it gets the story right, but it will go to great lengths to sound coherent. Michael Gazzaniga discovered this in his work with commissurotomized patients -- patients who had the two hemispheres of the brain surgically separated for the relief of intractable epilepsy. Much of the inputs and outputs of the brain are contralateral -- the left brain controls movement in the right half of the body, and the left brain processes information that your right eye sees. A picture of a chicken's talon was shown to a patient's left brain, and a snow-covered house to his right brain (through his right and left eyes respectively). A barrier limited the sight of each eye to only one picture. The patient was then asked to select from an array of pictures the one that was most closely associated with each of the two items. The patient pointed to a chicken with his left brain (that is, his right hand) and he pointed to a shovel with his right brain. So far, so good; chicken goes with talon, and shovel with a snow-covered house. But when Gazzaniga removed the barrier and asked the patient why he had chosen the shovel, his left hemisphere saw both the chicken and the shovel and generated a story that was consistent with both images. 'You need a shovel to clean out the chicken shed,' the patient answered, with no awareness that he had seen a snowbound house (with his nonverbal right brain), or that he was inventing an explanation on the spot. Score another piece of evidence for the constructivists."
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