Date Published: December 17, 2009
Publisher: Public Library of Science
Author(s): Thomas S. A. Wallis, Mark A. Williams, Derek H. Arnold, Bart Krekelberg. http://doi.org/10.1371/journal.pone.0008324
Abstract: Motion-defined form can seem to persist briefly after motion ceases, before seeming to gradually disappear into the background. Here we investigate if this subjective persistence reflects a signal capable of improving objective measures of sensitivity to static form.
Partial Text: A visual form that is camouflaged when stationary but revealed by motion can be said to be motion-defined. An interesting situation can ensue when a form is revealed by motion and then motion suddenly stops. Observers often experience a perceptual persistence, such that the motion-defined form remains subjectively visible for a brief interval in the absence of movement, before seeming to fade into the background and disappear from view , , , , , . These transiently persisting forms do not subjectively appear to move, nor do they seem to persist if the entire display is removed .
These experiments used a visual display that we refer to as a “dot-view” stimulus (see Figure 1, Methods, Movie S1 and Movie S2). Conceptually, this stimulus is very similar to multi-aperture displays  and slit-view displays, , , , . The signal-to-noise ratio of the display was adjusted to make waveforms difficult to detect when stationary, but clearly visible when moving. The signal-to-noise ratios (0.33 in Experiment 1, 0.25 in Experiments 2 and 3) used in the reported Experiments were selected in order to avoid ceiling and floor effects for sensitivity judgments. Appropriate signal-to-noise ratios for this purpose were determined via a preliminary experiments.
Previous studies have assumed that motion-defined form can briefly facilitate subsequent static form sensitivity, resulting in a transient perceptual persistence of the form after motion offset , , , , . Our study suggests this assumption is sound. We have demonstrated that pre-exposure to a moving form can enhance performance in objective measures of sensitivity to alignments of static forms. This cannot simply be attributed to movement providing the observer with a greater number of perspectives of the form, as pre-exposure to scrambled animations did not result in an equivalent facilitation. Nor can the facilitation be attributed to the remembered position at motion offset, as the facilitation was eliminated by the removal of the test waveform at motion offset.