Some Aspects of the Selective Process in the Functional Visual Field

A review is given of a group of experiments on performance as a function of display angle, aiming at a description of the perceptual strategies used with signals at various angular separations. The first experiments were carried out using a simple four-choice discrimination task. The results show a non-linear decrease of performance as a function of display angle, which proved to be related to the necessity of making eye and head movements when shifting from one signal source to the other. It is suggested that the non-linearity is due to changes of strategy and a preliminary theory about selective processes is formulated and tested in a number of tasks