Filled-space illusion caused by continuous distractor

Abstract

In the filled – space illusion, the filled part of stimuli seems longer in juxtaposition with the empty one. The aim of present study was to try to develop a quantitative model capable to account the illusory effects induced by stimuli with continuous and discrete distractors. In present study, we examined the strength of the filled-space illusion as a function of degree of contextual continuous filling of the referential interval of the three-dot stimulus. In the first series of experiments, the length of the line segment (placed in the centre of the referential interval) varied from zero to complete filling of the interval. In the second one, the length of the segment was constant but the extension of the referential interval varied (the positions of the terminal spots of the referential interval moved aside from the line segment ends symmetrically, thus, forming the empty gaps and producing discontinuities in the filling). Subjects adjusted the length of the empty test interval to that of the reference, and the matching errors were considered as the illusion magnitude. The data obtained showed regular overestimation of the referential interval with completeness of the interval filling. The dependencies established were used to develop a new quantitative model, which was successfully applied to fit the[...].