Human psychophysical analysis of receptive field-like properties: IV. Further examination and specification of the psychophysical transient-like function.

In this paper we examine several key properties of the moving 'windmill' target used in evaluation of the psychophysical transient-like function. Magnitude of the transient-like function, herein defined as the difference in threshold-determining background field luminance between stationary and moving windmill conditions, was greatest for a rate of approximately 6-8 on-off transitions/second for the moving windmill. Increasing the light/dark ratio of the windmill also augmented the magnitude of the transient-like function. The one-, two- and four-section 'windmill' targets exhibited essentially similar results, indicating that the number and length of borders do not influence this response. In conjunction with previous stationary windmill results (Enoch and Johnson, 1976), these data define the relevant transient-like function properties and provide a basis for comparison with findings in the companion paper (Enoch, Johnson & Fitzgerald, 1976a) which describes the application of these properties to clinical populations for diagnostic purposes.