Testing day: The effects of processing bias induced by Navon stimuli on the strength of the Müller-Lyer illusion

Age-Related Decline of Low-Spatial-Frequency Bias in Context-Dependent Visual Size Perception

Global precedence has been found to decline or even shift to local precedence with increasing age. Little is known about the consequence of this age-related decline of global precedence on other aspects of older adults’ vision. The global and local processing has been preferentially associated with the low-spatial-frequency (LSF) and high-spatial-frequency (HSF) channels, respectively. Here, we used low- and high-pass filtered faces together with the Ebbinghaus illusion whose magnitude is an index of context sensitivity. The results demonstrated that, relative to HSF faces, prior exposure to LSF faces increased the illusion magnitude for younger participants, but it reduced the illusion magnitude for older participants. Significant age group difference was observed only with prior exposure to LSF faces but not to HSF faces. Moreover, similar patterns of results were observed when the filtered faces were rendered invisible with backward masking, and the magnitude of age-related decline was comparable to the visible condition. Our study reveals that LSF-related enhancement of context sensitivity declines with advancing age, and this age-related decline was independent of the awareness of the spatial frequency information. Our findings support the right hemi-aging model and suggest that the magnocellular projections from subcortical to cortical regions might also be vulnerable to age-related changes.

Visual illusion and line bisection: a bias hypothesis revisited

It is generally accepted that visual illusions affect line bisection in the predicted direction. However, it has been reported an illusionary bias which seems questioning such general view. In a previous study, participants bisected lines flanked at both ends by two pairs of arrows, pointing in the same direction. The medialmost vertices of one pair converged on the line (converging arrows), whereas those of the other pair did not (non-converging arrows). Participants bisected lines toward the base of the arrows, i.e., toward the wider end of the stimulus and in the direction opposite to that predicted by the Baldwin illusion. However, the bisection bias was also directed away from the location of the converging arrows. We investigated what is the main factor affecting line bisection: arrows orientation, as previously suggested, or interference effects related to the location of converging arrows. In experiment 1, participants bisected lines flanked by converging versus non-converging arrows. Results confirmed the presence of a bisection bias directed not only toward the base of the converging arrows but also away from their location. In experiment 2, the arrows were located more internally, so that their medialmost vertices always converged on the line. Results showed that the bisection bias was directed away from the location of the arrows regardless of their orientation. It is suggested that the previously reported bisection bias did not depend on arrows orientation, but rather on interference effects related to converging arrows position. The theoretical implications of the results are discussed.