Quantitative Models of Face Cognition 1 Quantitative Models of Perceiving and Remembering Faces :

Quantitative Models of Face Cognition 2 The purpose of this initial chapter is to provide a general sketch of the problems that must be addressed in quantifying the representations and processes involved in converting an image of a face into a meaningful cognitive object. Our approach is to deene a structural model of the process components and to point out implicit connections among the logical, computational, and psychological pieces of the problem. We will consider especially the numerous potential connections among computational, psychophysical, and traditional information processing approaches that have not been made explicit in the literature. In this way, we hope to help readers organize the chapters that follow into the component parts of a complicated, multifaceted, but (we believe) ultimately tractable problem. We also hope to convince readers who may not regularly consume computational and/or mathematical material that the approaches we discuss are natural formalizations of theoretical concepts with which most psychologists are quite familiar and that the development and application of these formalizations are well-worth pursing. We think that mathematical and computational formalizations of the problem can provide a uniied framework for understanding face processing at a level that supersedes its individual components. Although we are still far from doing research at this \higher" level, we can at least begin to see where some of these potential lines of inquiry may lie. The psychological concepts that we believe readers will nd familiar in this chapter concern issues of measurement, representation, and task demands. These are issues encountered in nearly all models of psychological phenomena. Speciically, we will ask the following kinds of questions. How do you measure the information in a stimulus when the stimulus is a face? How do we represent sub-categories of stimuli, e.g., for faces, male and Quantitative Models of Face Cognition 3 female, young and old? Finally, how do the demands of the task and the nature of the processor constrain our access to and use of the information in the representation? This chapter is organized as follows. We rst give a brief overview of the kinds of tasks we must accomplish with human faces. This deenes the nature and diversity of the output that computational models must produce to be considered successful. We next present a general abstract framework for face perception and memory in terms of a \face space" representation (Valentine, 1991). This model implicitly or explicitly underlies much current psychological …