Ragnar Steingrimsson, Ph.D. - US grants

In studying sensory experience, a primary goal is to describe explicitly how sensations relate to the underlying physical stimuli. Although both physical stimuli and a person's behavioral responses are relatively easy to observe, a preeminent problem is to gain a handle on the unobservable intervening sensation. For example, if a patient judges a pain to be 4 on a 10-point scale, is that twice as much pain as a 2? Or, if two people judge a pain to be 4, how can we compare their experiences? For more than a century, these general issues have been studied intensely. Despite that long history and considerable progress, the problems are still far from completely solved, in part, because much past research has not been expressed in the form of testable foundational assumptions, formulated as explicit mathematical laws. The elaboration and testing of such is pivotal to progress in many areas of psychological science.

With support of the National Science Foundation, Drs. Duncan Luce, Louis Narens, and Ragnar Steingrimsson will continue their work in establishing a general, empirically-based, mathematically-expressed foundation of psychological measurement. In particular, the investigators will apply their general approach to the study of sensations. Experiments in both the auditory and visual domains will be used to evaluate the adequacy of behavioral axioms and, thus, of the numerical representations derived from them. The research extends their theoretical and empirical work to several topics including the effects of temporal or spatial order of stimulus presentation, sequential effects, and evaluating how observations obtained using different methodologies are related. An important aspect is the adequacy with which representations can accommodate individual differences without any statistical fitting of unspecified functions and free parameters. Successful progress on this program promises much unification of now separate theories, notably those involving intensity, frequency, and presentation order, and theories that treat those in a domain-specific fashion, and the relations between and evaluation of different methodologies.

The categorization of color has been extensively studied by linguists, anthropologists, and psychologists for more than 100 years. It is an ideal subject matter for cross-cultural, comparative, and historical studies because the physiological processing of color is well-understood, there are established psychological models of perceptual color appearances, there are accepted methods for measuring color appearances and cataloging them for industrial use, and there are large data sets that include a wide variety of languages used by various ethnolingusitic populations to name and classify colors. This large interdisciplinary literature includes a number of long-lasting controversies, the most prominent being the degree to which color naming systems are based on universal aspects of physiological processing (universalism) versus cultural aspects (relativism). One reason the universalism-relativism issue has been long-lasting is that there has been a lack of a mathematically based methodology to recreate the possible paths that evolving color naming systems may take. This deficiency obstructs appropriate evaluations of the roles of relevant universalist and relativist mechanisms.

The project will continue the investigators' work developing a methodology for evolving color categories in manners that are applicable to outstanding theoretical and empirical issues in color naming research. In particular, methods of evolutionary game theory of economics will be applied to the problem of the social evolution of psychological color categories. The core of the theory is that the semantics of color terminology is used for the efficient transmission of color information weighted by the importance of the information. Psychology puts constraints on what semantics should be used in terms of communication efficacy and culture puts constraints on which semantics should be used in terms of cultural importance. The research also looks at how efficient semantic codes evolve in populations containing subpopulations of color impaired observers. (The research literature on color naming generally excludes this impaired class of observers in data collection and theoretical modeling, although there are a few exceptions.) The research also has industrial applications to situations involving colonies of robots evolving linguistic categorization schemes for efficient communication among themselves and for efficient translation into human languages.