Abstract
Recent studies have suggested that temporal dynamics rather than symmetrical motion-direction contribute to mirror-symmetry perception. Here we investigate temporal aspects of symmetry perception and implicitly, its temporal flexibility and limitations, by examining how symmetrical pattern elements are combined over time. Stimuli were dynamic dot-patterns consisting of either an on-going alternation of two images (sustained stimulus presentation) or just two images each presented once (transient stimulus presentation) containing different amounts of symmetry about the vertical axis. We varied the duration of the two images under five temporal-arrangement conditions: (a) whole patterns in which a symmetric pattern alternated with a noise pattern; (b) delayed halves—the halves of the symmetric and noise patterns were presented with temporal delay; (c) matched-pairs—two alternating images each containing equal amounts of symmetrical matched-pairs; (d) delayed matched-pairs—the same as arrangement (c), but with matched-pairs presented with delay; and (e) static—both images presented simultaneously as one. We found increased sensitivity in sustained compared to transient stimulus presentations and with synchronous compared to delayed matched-pairs stimuli. For the delayed conditions, sensitivity decreased gradually with longer image durations (>60 ms), prominently for the transient stimulus presentations. We conclude that spatial correlations across-the-symmetry-midline can be integrated over time (∼120 ms), and symmetry mechanisms can tolerate temporal delays between symmetric dot-pairs of up to ∼60 ms.
Highlights
Mirror symmetry ( ‘‘symmetry’’) is a ubiquitous visual feature in natural images that occurs when one half of an image reflects the other about an axis
Several recent studies have examined the contribution of simple visual attributes, such as luminance-polarity and color (Gheorghiu, Kingdom, Remkes, Li, & Rainville, 2016; Morales & Pashler, 1999; Wu & Chen, 2014), stereoscopic depth (Ishiguchi & Yakushijin, 1999; Treder & van der Helm, 2007), and motion direction (Sharman & Gheorghiu, 2017) to symmetry perception, little or nothing is known about the temporal dynamics of symmetry perception
We examine temporal properties of symmetry perception in response to sustained and transient stimulus presentations by using dynamic stimuli consisting of an on-going alternation of two images or only two images containing varying amounts of symmetry about the vertical axis
Summary
Mirror symmetry ( ‘‘symmetry’’) is a ubiquitous visual feature in natural images that occurs when one half of an image reflects the other about an axis. While recent studies have suggested that temporal dynamics contribute to symmetry perception (Sharman & Gheorghiu, 2017), none have considered temporal aspects of symmetry perception in dynamic stimuli In this communication, we investigate sustained and transient properties of symmetry perception about vertical axis by examining how symmetrical patternelements are combined over time, and whether symmetry mechanisms can tolerate temporal delays between matched elements. We investigate sustained and transient properties of symmetry perception about vertical axis by examining how symmetrical patternelements are combined over time, and whether symmetry mechanisms can tolerate temporal delays between matched elements By studying both sustained and transient aspects of symmetry perception, one can gain insight into the temporal characteristics of the Citation: Sharman, R.
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