THE EVOLUTION OF PSYCHOPHYSICS: FROM SENSATION TO COGNITION AND BACK AGAIN
For over a century, psychophysicists have attempted to understand the processes by which physical properties of stimuli are mapped into mental representations. Early investigations followed a model in which physical energy was transduced into neural impulses, with the information in these impulses being conveyed to the central nervous system where they gave rise to sensations (a bottom-up information-processing model). Even when it was recognized that there were interactions among stimuli (e.g., center-surround contrast in vision), these interactions were assumed to occur early in the information-processing stream (e.g., on-center and off-surround receptive fields). Hence, the implicit bias towards a bottom-up process remained. Within the last 40-50 years, however, it has become apparent that top-down factors affect how information is gathered and processed. These recent developments have forced us to refine our models to include sensory-cognitive interactions.