Influence of subject's viewing behaviour on grey settings

Jürgen Golz
Christian-Albrechts-University of Kiel, Institute for Psychology

In numerous studies on colour constancy or colour induction subjects have to adjust a test spot such that it looks achromatic. Subject's viewing behaviour during these settings are often not controlled or reported. Here I will show that it can have a substantial impact on the results of grey settings in variegated surrounds whether and to what degree the subject visually explores the stimulus by looking around in the surround or whether the subject focuses on the test spot.

In a series of experiments, different viewing instructions and techniques manipulating the degree of visual exploration of the surround are compared with respect to the degree of constancy as measured by the shift of grey settings in coloured surrounds. The main result is that in variegated surrounds (but not in homogeneous surrounds) ample exploration can increase colour constancy compared to focussing the test spot by as much as 20% (100% colour constancy meaning that the subject chooses as grey the average chromaticity of the surround). Thus, if this factor is not experimentally controlled, it can inflate variance, lead to questionable conclusions and reduce comparability between different studies.