Effects of Change in Stimulus Background on Performance of a Visual Task

Abstract

THE effects of varying the auditory and visual characteristics of irrelevant background stimulation on auditory vigilance tasks have been investigated intensively¹. While the introduction of incidental stimulation in such a situation is usually detrimental to performance, in some conditions performance may be facilitated by the presence of such stimulation. It has been demonstrated that the rate of detection of an auditory signal increased when subjects were exposed to varying irrelevant visual stimuli², but no research seems to have been directed at investigating the effect of varying the visual background information on the performance of a visual task. The present study seeks to do this, using printed material. The experimental hypothesis derives from Berlyne's^3,4 extension of Hullian theory to the field of attention. He suggested that changes in a stimulus array counteracted the “conditioned inhibition” of Hull⁵, which it is assumed develops during responding to an ongoing series of similar stimuli, leading to a tendency not to respond. This implies that the perceptual response to a changing stimulus series will be greater than to an unchanging one. It is supposed here that the same consideration applies to the stimulus setting as to the stimulus. Thus it is predicted that periodic changes, in this case of colour, in the background of a series of visual stimuli, which are themselves changed only within narrow limits, will increase the proficiency with which the stimulus series is attended to and processed.