Story of Psychology - Morton Hunt [341]
—In the late 1980s Daniel L. Alkon and his colleagues at the
National Institute of Neurological and Communicative Disorders and Stroke trained a sea snail, Hermissenda crassicornis, to respond to light in a way it does not normally do. Hermissenda instinctively swims toward light; also, when the water is turbulent it instinctively clenches its foot muscle in order to cling to a surface. Alkon combined these reactions. By flashing a light and simultaneously whirling the chamber in which he housed the snail, he conditioned it—taught it—to clench its foot muscle whenever it saw a flash of light. He then found that in certain of the snail’s photoreceptor neurons, molecules of PKC, a calcium-sensitive enzyme, had moved from the interior of the neuron toward its membrane, where they reduced potassium-ion flow—a partial explanation of memory in molecular terms.18
—Over several decades, James L. McGaugh and other researchers did a number of studies in which they injected epinephrine (a hormone produced by the adrenal gland) and other catecholamine neurotransmitters into rats after training them to run a maze. Epinephrine, in particular, causes the rats to remember longer what they learned than rats not so dosed. The explanation, deduced from other studies, seems to be that a byproduct of the epinephrine combats opioids, a group of neurotransmitters that serve useful purposes but plug up receptors on the receiving side of synapses. The result: more receptors remain open, the synapses function more efficiently, and memory is strengthened.19
These and many other research studies made cognitive neuroscientists feel sure that they were on the right track to explaining the many mysteries of psychology. Their approach promised to end, once and for all, the ancient debate about body and mind by explaining all mental processes in terms of material substances and events. All high-level mental processes such as memory, language, and reasoning were only ions and molecules flowing hither and thither in the labyrinthine and infinitesimal plumbing of the brain.
But the great majority of cognitive psychologists, proud of their new dominance and excited by the amazing capacity of computers to mimic—and perhaps explain—human reasoning, were dismissive of cognitive neuroscience. In the 1950s, after Newell and Simon’s dramatic presentation of Logic Theorist, whatever connection had existed between cognitive psychology and neuroscience fell apart; Simon, in fact, authoritatively declared that to “understand cognition, one needn’t pay much if any attention to the underlying biology.”20
For the next twenty-five or so years, most cognitive psychologists agreed with him, insisting that neural events do not provide an adequate or useful explanation of cognitive phenomena. Few were dualists in the sense of believing in immaterial mind, but they asserted that psychological processes, though constructed of neural events, were properties of the organization or metastructure of those components, not of the components themselves, even as shelter is not a property of bricks, beams, and shingles but of a house built of them.
Nobel Laureate Roger Sperry, though himself a brain scientist, offered another analogy: a higher-order mental process is like a wheel rolling downhill—the rolling is determined by the “overall system properties” of the wheel, not by the atoms and molecules of which it is made.
The developmentalist Jerome Kagan used a different analogy: the elegant laws of planetary motion illustrate phenomena that are not expressible in terms of the atoms of which the planets are made.
Another analogy, this from the cognitive scientist Earl Hunt: “We can tell from physical measures that the left temporal region of the brain is active when we read, but we cannot discriminate the activity induced by reading Shakespeare from that induced by reading Agatha