August 2014
Volume 14, Issue 10
Vision Sciences Society Annual Meeting Abstract  |   August 2014
Tracking Illusory Contour Figures
Author Affiliations
  • Natasha Dienes
    University of Guelph
  • Lana Trick
    University of Guelph
Journal of Vision August 2014, Vol.14, 348. doi:
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      Natasha Dienes, Lana Trick; Tracking Illusory Contour Figures . Journal of Vision 2014;14(10):348. doi:

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

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In static displays, search is inefficient when participants are looking for targets that differ from distractors in line-orientation for objects defined by Kaniza-style illusory contours (disconnected pac-men lined up to create the impression of contours); the same search is efficient for objects defined by actual (connected luminance-based) contours (e.g., Li, Cave & Wolfe, 2008). This suggests that illusory-contour defined line-orientation cues cannot guide the attentional focus to targets in the same way as the same cues can when targets are defined by actual contours, and this in turn may indicate more attentional demands when defining objects as wholes. However, it is unclear whether illusory-contour defined targets are also more difficult to track than those defined by actual contours when items move. On the one hand, the Gestalt cue "grouping by common fate" may be such a powerful indication of object-hood that it wipes out any benefit of real over illusory contours in multiple-object tracking (MOT). On the other, it is possible that static and dynamic cues both contribute to helping objects maintain their integrity during MOT; thus there may be attentional costs to having to draw together the disconnected elements in illusory-contour figures: one that may only reveal itself once the tracking task becomes demanding (with more targets). MOT performance was compared for 1, 3, and 5 targets when all items (targets and distractors) were defined by actual as compared to Kaniza-style illusory contours. In a second experiment, the task was made even more difficult by making the pac-men inducers within individual Kaniza figures differ in contrast polarity (some darker than the background and others lighter), a difference that promoted grouping parts of targets with parts of distractors in static displays (i.e., grouping by similarity in terms of contrast). Results underline similarities and differences between static and dynamic tasks.

Meeting abstract presented at VSS 2014


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