Here are some demonstrations of the various phenomena and manipulations discussed in the following paper:
New, J. J., & Scholl, B. J. (2008). 'Perceptual scotomas': A functional account of motion-induced blindness. Psychological Science, 19(7), 653-659.These demonstrations are provided as Quicktime movies, which can be downloaded or viewed directly in most web-browsers. (To download a free Quicktime player, go here.) 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.
Previous studies have explored several proximal factors that mediate MIB, but there is little consensus on why it occurs at all. Here we explore a new possibility: rather than being a failure of visual processing, MIB may be a functional product of the visual system's attempt to separate distal stimuli from artifacts of damage to the visual system itself. When a small object is invariant with respect to changes that are occurring to a global region of the surrounding visual field, the visual system may discount that stimulus as akin to a scotoma, and may thus expunge it from awareness. Our paper discusses how this theory can account for several previous MIB results, and describes three new effects that were directly predicted by this view.
Demonstration #1: The Basic MIB Display (7.3 MB; 30 seconds)
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 #2a: Congruent Fixation/Target Motion (3.3 MB)
Demonstration #2b: Incongruent Fixation/Target Motion (3.3 MB)
Sample animations of the two displays used in Experiment 1. Observeres visually tracked the slowly moving fixation circles while peripherally attending the yellow disc. MIB was stronger than when the target and the fixation moved together (as in Demo #2a), compared to when the target and the fixation moved in opposite directions (as in Demo #2b) -- perhaps because most types of visual injuries will be retinally stable, and thus 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: A Disappearing Object (4.3 MB)
Demonstration #3b: A Disappearing Hole (4.6 MB)
Sample animations of the two displays used in Experiment 2. Observers fixated the central fixation point and peripherally attended either the circular target grid (in the Target condition) or the circular hole in the grid covering the entire upper left quadrant of the display (in the Hole condition). Observers readily reported that the circular grid-object disappeared, confirming that MIB can be obtained in this type of display. The key result was then that the 'hole' also disappeared -- i.e. was filled-in with the surrounding grid. This confirms that MIB is an active process that interpolates on the basis of the surrounding texture.
Demonstration #4a: Cyclic Luminance Changes (2.8 MB)
Demonstration #4b: Motion Control for Cyclic Luminance Changes (2.5 MB)
Sample animations of two of the displays used in Experiment 3. Because the 'perceptual scotoma' theory's logic applies regardless of the type of global change to the visual field, an anomalous target may be judged as unlikely to be in the outside world even if the conflict does not involve any motion -- as confirmed by the occurrence of MIB during global cyclic luminance variations, as in Demo #4a.