September 2021
Volume 21, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2021
Task set and instructions influence the relative weight of figural priors in figure-ground organization
Author Affiliations
  • Tandra Ghose
    TU Kaiserslautern
  • Mary Peterson
    University of Arizona, Tucson
Journal of Vision September 2021, Vol.21, 2427. doi:
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      Tandra Ghose, Mary Peterson; Task set and instructions influence the relative weight of figural priors in figure-ground organization. Journal of Vision 2021;21(9):2427.

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      © ARVO (1962-2015); The Authors (2016-present)

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In 100 years since the figure-ground phenomenon was first discussed by Rubin (1921), very little attention has been paid to the importance of task set and instructions on the outcome of figure-ground organization. Here we test whether changes in task set and instructions can alter the outcome of the cross-border competition between figural-priors that underlies figure-assignment. In figure-ground organization, the figure is defined as a region that is both “shaped” and “nearer”. Extremal edge (EE), a relative distance prior, has been established as a strong figural prior when the task is to report “which side is nearer?” In a within subject experiment using bipartite stimuli, EEs competed and cooperated with familiar-configuration, a shape prior for figure assignment. The experiment consisted of two blocks marked by the presence (Block-A) vs. absence (Block-B) of instructions emphasizing that familiar objects might be present. Within each block, two sub-blocks, one for each task set: “which side is shaped?” and “which side is nearer?” were counterbalanced across participants. Data from 24 participants for Block-A showed small but significant effects of familiar-configuration for displays sketching upright familiar objects, although “shaped-side” responses were predominantly determined by EEs. In Block-B, instructions regarding the possibility of perceiving familiar shapes were added. Now, although EE remained the dominant prior, the figure was perceived on the familiar-configuration side of the border on a significantly larger percentage of trials across all display types. With familiarity thus “primed”, effects of task set emerged when EE and familiar-configuration favored opposite sides as figure. Thus, changing instructions can modulate the weighing of figural priors for shape versus distance in figure assignment in a manner that interacts with task set. Moreover, we show that the influence of familiar parts emerges in participants without MTL/PRC brain damage when instructions emphasize that familiar objects might be present.


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