Further explorations of 'perceptual scotomas'
Here are some demonstrations of the various phenomena and manipulations discussed in the following paper:
New, J. J., & Scholl, B. J. (under review). Motion-induced blindness for dynamic events: Further explorations of the 'perceptual scotoma' hypothesis. Manuscript submitted for publication.These demonstrations are provided as Flash animations, which can be downloaded or viewed directly in most web-browsers. These movies are a bit large and choppy, but they should be sufficient to illustrate the basic manipulations. If you have any trouble viewing the movies, downloading them and then playing them from your local hard-drive may help. As highly compressed versions of the original stimuli constructed for demonstration purposes, these movies may not preserve the precise spatial and temporal characteristics of the originals.
Motion-induced blindness (MIB) is a striking phenomenon in which fully visible and attended objects will repeatedly fluctuate into and out of conscious awareness when superimposed onto certain global moving patterns. Whereas previous accounts have explained MIB by appeal to a limitation or failure of visual perception, we have recently proposed the perceptual scotoma hypothesis (New & Scholl, 2008, Psychological Science) which interprets MIB as a functional inference in visual processing -- eliminating some stimuli from awareness in much the same way that the visual system identifies and compensates for some visual impairments. Here we report several new features of MIB that were uniquely motivated by the perceptual scotoma account. These results demonstrate how the perceptual scotoma account can generate novel predictions, and are consistent with the idea that MIB reflects a functional 'unconscious inference' in visual processing.
Demonstration #1: The Basic MIB Display (24 KB)
One of the most striking experimental manipulations of visual awareness is that of motion-induced blindness (MIB), wherein salient objects in full view can repeatedly fluctuate into and out of conscious awareness when superimposed onto certain global moving patterns. Here is a basic example: Fixate the concentric white circles and attend to the moving blue crosses, and then notice what happens to the otherwise-salient yellow disc. This display is similar to previous MIB experiments.
Demonstration #2: Positional Invariance with Multiple Targets (64 KB)
Observers visually tracked the slowly translating fixation circles while peripherally attending to the two target discs that were also moving in the upper left region of the display. MIB was stronger for the target that moved in step with fixation compared to the target that moves in the opposite direction as fixation. Because most types of visual injuries are retinally stable, an anomalous target may be judged as less likely to be in the outside world if it is moving with fixation vs. relative to fixation.
Demonstration #3a: Luminance Distortion (661 KB)
Demonstration #3b: Contraction Distortion (641 KB)
Demonstration #3c: Expansion Distortion (655 KB)
Demonstration #3d: Curvature Distortion (705 KB)
Demonstration #3e: Color Distortion (673 KB)
Observers fixated the central fixation point and peripherally attended to a target defined by the persistent distortion of mask elements passing through a small region in the upper left quadrant of the display. Such manipulations are similar to local visual disturbances resulting from scotomas that are not entirely opaque and thus only attenuate or distort stimuli within affected regions. These 'active' targets all disappeared due to MIB.
Demonstration #4: Floating Blindspots (64 KB)
Observers fixated the central fixation point circles while peripherally attending the slowing moving yellow disc. MIB was stronger when the target settled slowly downward -- as would a 'floater' drifting within the eye during fixation -- compared to when the target drifted upward.