Influence of peripheral degradation on the identification of eccentric targets (revised)

When the peripheral field is degraded, or 'modulated', as occurs with certain corrective lenses, identification of a peripheral image requires combined head and eye movements to place the image within a relatively clear section of the field. In such cases the time required to identify a peripheral object increases systematically. Previous experiments involving severely restricted peripheral fields (slit viewing) have indicated that the increase in identification time is primarily determined by the dynamics of the head movement. Head movement characteristics, in turn, are related to the nature of the peripheral distortion. To describe more complex peripheral distortions, a 'modulation' function is developed which provides a realistic, quantitative measure of the deficit induced by a given distortion. Modification in head movement can be traced directly to the influence of this modulation function.