Sensation and Judgment: Complementarity Theory of Psychophysics

Sensation and Judgment: Complementarity Theory of Psychophysics

Sensation and Judgment: Complementarity Theory of Psychophysics

Sensation and Judgment: Complementarity Theory of Psychophysics


Psychophysical theory exists in two distinct forms -- one ascribes the explanation of phenomena and empirical laws to sensory processes. Context effects arising through the use of particular methods are an unwanted nuisance whose influence must be eliminated so that one isolates the "true" sensory scale. The other considers psychophysics only in terms of cognitive variables such as the judgment strategies induced by instructions and response biases. Sensory factors play a minor role in cognitive approaches.

This work admits the validity of both forms of theory by arguing that the same empirical phenomena should be conceptualized in two alternative, apparently contradictory, ways. This acceptance of opposites is necessary because some empirical phenomena are best explained in terms of sensory processes, while others are best ascribed to central causes.

The complementarity theory stresses the "mutually completing" nature of two distinct models. The first assigns importance to populations of sensory neurons acting in the aggregate and is formulated to deal with sensory effects. The second assigns importance to judgment uncertainty and to the subject strategies induced by experimental procedures. This model is formulated to explain context effects. Throughout the text, the exposition is interlaced with mathematics, graphs, and computer simulations designed to reveal the complementary nature of psychophysical explanations.


An empirical science invites characterization in one of two distinct ways. Either the field appears as a singular whole with all the parts fitting together in just the right places, or the field appears strewn with the disconnected results of experimental tests. Confronted with the first situation, the theorist can "admire" the packaging or take steps to "unwrap" it. Confronted with the second situation, the theorist can refuse the challenge or attempt to combine the pieces into a new whole. in this way, theoretical efforts undergo cyclical shifts in emphasis. Once a neat package is assembled, the chief option is to unwrap the packaging, and once this is done, the chief option is to reassemble the facts into a new arrangement. the field waxes and wanes, with each succeeding cycle leading to a deeper understanding of the empirical phenomena.

In this book I offer a theory to unify the apparently disconnected findings of psychophysics. I argue that some experimental outcomes are best attributed to sensory processes, whereas others are best attributed to judgment processes. Other results can be viewed equally well from either perspective. the two alternatives each have special advantages, and together they provide a dual characterization of the field that is complementary and "mutually completing."

The first chapter outlines the overall theme of the book, followed by six chapters discussing the implications of a sensory orientation to psychophysics. This section considers the major psychophysical laws (Weber, Stevens, and Piéron) and suggests how these laws interrelate at the neural level. Chapter 7 ends the first part of the book by extending the reach of sensory modeling to memory psychophysics.

The next two chapters (8 and 9) introduce the judgment orientation to psychophysics, and succeeding chapters (10 through 15) detail the implications of this . . .

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