Searching for illusory motion

An Illusory Motion in Stationary Stimuli Alters Their Perceived Duration

Despite having equal duration, stimuli in physical motion are perceived to last longer than static ones. Here, we investigate whether illusory motion stimuli produce a time-dilation effect similar to physical motion. Participants performed a duration discrimination task that compared the perceived duration of static stimuli with and without illusory motion to a reference stimulus. In the first experiment, we observed a 4% increase in the number of "longer" responses for the illusory motion images than static stimuli with equal duration. The time-dilation effect, quantified as a shift in the Point of Subjective Equality (PSE), was approximately 55 ms for a 2-second stimulus. Although small, the effect was replicated in a second experiment in which the total number of standard-duration repetitions was reduced from 73 to 19. In the third experiment, we found a positive linear trend between the strength of the illusory motion and the magnitude of the time-dilation effect. These results demonstrate that, similar to physical motion stimuli, illusory motion stimuli are perceived to last longer than static stimuli. Furthermore, the strength of the illusion influences the extent of the lengthening of perceived duration.

Action Video Game Players Do Not Differ in the Perception of Contrast-Based Motion Illusions but Experience More Vection and Less Discomfort in a Virtual Environment Compared to Non-Action Video Game Players

Action video game players (AVGPs) show enhanced visual perceptual functions compared to their non-video game playing peers (NVGPs). Whether AVGPs are more susceptible towards static contrast motion illusions, such as Fraser Wilcox illusions, has not been addressed so far. Based on their improved perceptual skills, AVGPs are expected to be more susceptible to the illusions and perceive more motion in them. The experience of illusory self-motion (vection) is believed to be dependent on top-down attentional processes; AVGPs should therefore experience stronger vection compared to NVGPs based on their improved attentional skills. Lastly, due to their extensive prior experience with virtual environments, AVGPs should experience less discomfort in VR compared to NVGPs. We presented rotating and expanding motion illusions in a virtual environment and asked 22 AVGPs and 21 NVGPs to indicate the strength of illusory motion, as well as the level of discomfort and vection experienced when exposed to these motion illusions. Results indicated that AVGPs and NVGPs perceived the same amount of motion when viewing these illusions. However, AVGPs perceived more vection and less discomfort compared to NVGPs, possibly due to factors such as enhanced top-down attentional control and adaptation. No differences in the perception of expanding and rotating illusions were found. Discomfort experienced by AVGPs was related to illusion strength, suggesting that contrast illusions might evoke the perceived discomfort rather than the virtual environment. Further studies are required to investigate the relationship between contrast sensitivity, migraine and the perception of illusion in AVGPs which should include illusory motion onset and duration measures.

Visual Search in 3D: Effects of Monoscopic and Stereoscopic Cues to Depth on the Validity of Feature Integration Theory and Perceptual Load Theory

Previous research has successfully used feature integration theory to operationalise the predictions of Perceptual Load Theory, while simultaneously testing the predictions of both models. Building on this work, we test the extent to which these models hold up in a 3D world. In two experiments, participants responded to a target stimulus within an array of shapes whose apparent depth was manipulated using a combination of monoscopic and stereoscopic cues. The search task was designed to test the predictions of (a) feature integration theory, as the target was identified by a single feature or a conjunction of features and embedded in search arrays of varying size, and (b) perceptual load theory, as the task included congruent and incongruent distractors presented alongside search tasks imposing high or low perceptual load. Findings from both experiments upheld the predictions of feature integration theory, regardless of 2D/3D condition. Longer search times in conditions with a combination of monoscopic and stereoscopic depth cues suggests that binding features into three-dimensional objects requires greater attentional effort. This additional effort should have implications for perceptual load theory, yet our findings did not uphold its predictions; the effect of incongruent distractors did not differ between conjunction search trials (conceptualised as high perceptual load) and feature search trials (low perceptual load). Individual differences in susceptibility to the effects of perceptual load were evident and likely explain the absence of load effects. Overall, our findings suggest that feature integration theory may be useful for predicting attentional performance in a 3D world.