Impact of aging on perceptual asymmetries for horizontal and vertical stimuli in the greyscales task

Through the paper version of the grayscale task, this study examines the impact of aging and gender on horizontal and vertical pseudoneglect in healthy right-handed Japanese people. Participants included 168 (84 women and 84 men) healthy right-handed participants between the ages of 18 and 85, which were divided into three age cohorts (i.e., young, middle, and older). When administering the task, in the horizontal condition, the stimulus set of the grayscale task waspositioned at the center of the desk. In the vertical condition, the stimulus set was placed at the participants' eye level on the front screen. A reliable left bias was observed across all age groups in the horizontal task, although individual differences in the young group were significant. Moreover, gender differences and age-gender interactions were not confirmed. Similarly, in the vertical task, an upward bias was identified in both women and men across all age groups. Furthermore, there was a weak correlation between the horizontal and vertical bias index. These results were inconsistent with those of a previous study and other research using manual line bisection and landmark tasks. Further, we comprehensively deliberated on the cognitive/neural basis of horizontal and vertical pseudoneglect.