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In this first of two Hitchcock lectures, Professor Shepard will explore the relationship between how the mind represents the world and how these representations both enable and constrain thought experiments in physics. At the core of his argument is the notion that, through natural selection, the mind has come to reflect long-enduring properties of the world. To illustrate, Shepard will start with perception, and argue as follows:
Perception. Contrary to our intuitions, the process of perceiving the world is complex, and involves many inferences that go beyond the "sense data" (the retinal array). To be useful, these inferences must track the way the world really is. Natural selection has shaped the inference processes that guide perception, so that they reflect properties of the physical world, such as that it is locally three-dimensional and that objects move along certain kinds of smooth trajectories. He will illustrate this with demonstrations of apparent motion and perceptual illusions. Imagery. The same inferences govern our imagery system, thereby determining how our "mind's eye" imagines the world. In principle, our imagination could be designed so that it is just as easy to imagine an object moving along a random pathway as a smooth trajectory (for example). But that is not how our "mind's eye" is designed: instead, when we imagine the movements of objects, their movements track the way objects move in the external world - even in the absence of the constraining influence of perceptual stimuli. Shepard will illustrate this with experiments and demonstrations involving mental imagery.
Science. Many revolutions in physics have been driven not by new data, but by new thought experiments. But this raises the question, why do thought experiments help at all? Shepard argues that thought experiments have helped in physics to the extent that our mind's eye has come to internalize implicit physical and mathematical knowledge. He will illustrate this point by showing the connection between his data on how the mind represents the world and thought experiments by Galileo, Newton, and other figures from the history of physics.
In his second Hitchcock lecture, Shepard will argue that understanding
how the mind represents the world can provide a groundwork both for science
and for ethics. Under the heading, "The grounds of science", he will discuss
(a) Three realms of reality: My experience, your experience, and the reality
behind our experience; (b) The hierarchy of scientific laws (and the quest
for the "ultimate laws"); and (c) The empirical versus the mathematical.
Under the heading, "The grounds of ethics", he will discuss (a) Parallelisms
between science and ethics; (b) The materialist neglect of the experiential
and mathematical realities; (c) The grounds of the "Golden rule", Kant's
"categorical imperative", and Rawls's "theory of justice"; and (d) Whether
there can be an objective notion of "meaning" or "purpose."
Roger N. Shepard has made influential contributions to our understanding of visual and auditory perception, learning, generalization, memory, mental imagery, and the relation between evolutionarily long-standing properties of the world and the ways in which mental representations have come to reflect them. He also developed the first nonmetric method of multidimensional scaling, a technique used in hundreds of studies to derive quantitative models of mental structure from qualitative measures of similarity.
His books include Mental Images and Their Transformation (1982) and Mind Sights (1990).
Shepard is a member of the National Academy of Sciences, and a recipient of the New York Academy of Sciences Award in Behavioral Sciences, and of our nation's highest scientific honor: the National Medal of Science.
Shepard graduated from Stanford in 1951, and received his doctorate from Yale. He then held positions at Bell Labs and at Harvard University before going to Stanford, where he has been a member of the faculty for over 30 years.
Currently Shepard is the Ray Lyman Wilbur Professor of Social Science, Emeritus, and Professor of Psychology, Emeritus at Stanford University.
The Hitchcock Lectures, administered by the University of California,
are named in honor of Dr. Charles M. and Martha Hitchcock. Hitchcock's
1885 bequest set up a professorship for free lectures on scientific and
practical subjects. The Hitchcock Professorship has been in place from
1909. The list individuals who have held it includes Robert Millikan, Niels
Bohr, Enrico Fermi, H. A. Bethe, Edwin Hubble, Robert Oppenheimer, Freeman
Dyson, Stephen Hawking (physics); Linus Pauling, Ilya Prigogine (chemistry);
in evolutionary biology and/or zoology: Thomas Morgan, J.B.S. Haldane,
R. A. Fisher (also statsitics), Sewall Wright, G. G. Simpson, E. O. Wilson;
Claude Levi-Straus (anthropology); John Tukey, Frederick Mosteller, Benoit
Mandelbrot (statistics and/or mathematics); and, in psychology, Wolfgang
Kohler, Walter B. Cannon, Torsten Weisel, Eric Kandel, and Herbert Simon.
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