Motion induced blindness
Motion Induced Blindness (MIB) is a phenomenon of visual disappearance or perceptual illusions observed in the lab, in which stationary visual stimuli disappear as if erased in front of an observer's eyes when masked with a moving background. Most recent research has shown that microsaccades counteract disappearance but are neither necessary nor sufficient to account for MIB.[1]
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[edit] Overview
Motion-induced blindness was originally discovered by Ramachandran and Gregory in 1991.[2] However it was given more attention and named when rediscovered by Bonneh, Cooperman, and Sagi in 2001. The researchers originally attributed its causes strictly to attentional mechanisms, seeing the visual system as operating in a winner-takes-it-all manner.[3]
Troxler's fading, discovered by Troxler in 1804, is a very similar phenomenon in which an object away from one's focus of attention,disappears and reappears irregularly. There is no necessity for a moving background for this illusion to occur. Other similar phenomena in which salient stimuli disappear and reappear include binocular rivalry, discovered as early as 1593,[4] monocular rivalry,[5] and flash suppression.
[edit] Causes
The illusion catches the brain ignoring or discarding information. This may be one of the brain's useful tricks, a deficiency - or perhaps both. An ongoing debate regarding the causes of MIB is still present in today's vision research, however the purely attentional mechanism explanation has been rejected and new theories were put forward.
Surface completion
Numerous psychophysical findings emphasize the importance of surface completion and depth cues in visual perception. Thus, if MIB is affected by these factors it will regulate in accordance to simple occlusion principles. In their study, Graf et al. (2002) stereoscopically presented a moving grid stimulus set behind, in front of, or in the same plane as the static dots. They then showed involuntary completion of the grid elements into a surface interacting with the static targets - creating an illusion of occlusion.[6] When the grid appeared in front of the targets the proportion of disappearance was larger than when it was behind or on the same plane. Although to a lesser extent, MIB did nonetheless occur in the conditions were the perceptual occlusion was not taking place (targets were in front of the mask).
The effect of interposition and perceived depth on target disappearance in MIB was also shown in a study done by Hsu et al. (2010) where a concave target appearing behind its surrounding disappeared more frequently than a convex one appearing in front of the mask.[7] These effects, albeit being less significant, were replicated in similar settings without the use of motion.
The above experimets show that although MIB can be predictably modulated by surface completion and simple occlusion precepts, these do not seem to be giving an explanation for it occurring in the first place and may in fact be simply evoking different processes above MIB itself. Moreover, the surface completion theory does not explain the role of motion in this phenomenon.
Perceptual filling-in
Hsu et al. (2004) compared MIB to a similar phenomenon of perceptual filling-in (PFI), which likewise reveals a striking dissociation between the percept and the sensory input.[8] They describe both as visual attributes which are perceived in a certain region of the visual field regardless of being in the background (in the same manner as colour, brightness or texture) thus inducing target disappearance. They argue that because in both MIB and PFI the disappearance; or the incorporation of the background motion stimuli; becomes more profound with an increase in eccentricity, decrease in contrast and when perceptual grouping with other stimuli is controlled for; the two illusions are very likely to be a result of intermutual processes. Since MBI and PFI show to be structurally similar, it seems plausible that MIB can be a phenomenon responsible for completing missing information across the blind spot and scotomas where motion is involved.
Motion streak suppression
Rather than a deficiency of our visual processing, MIB may be a functional side effect of the visual system’s attempt to facilitates a better perception of movement. Wallis and Arnold (2009) propose a plausible explanation of target disappearance in MIB by linking it to the processes responsible for motion streak suppression.[9] In their view, target disappearance is a side effect of our vision's attempt to provide an apparent perception of moving form. MIB shows to be hindered at equiluminance and augmented at the trailing edges of movement, all reminiscent of motion streak suppression. It appears that what drives MIB is a competition between a neural signal sensitive to spatiotemporal luminance and one responding to proximate stationary targets; where the stronger signal eventuates with what we actually perceive at any given moment (Donner et al., 2008).[10]
Perceptual scotoma
A different explanatory approach by New and Scholl (2008) proposes that the phenomenon is another instance of our visual system's endeavor to provide clear and accurate perception.[11] Because the static targets appear to be invariant with respect to the background motion, the visual system removes them from our awareness, discarding it as being contrary to the logic of perception and real life situations; thus treating it as a piece of disaffiliated retina or a scotoma. Consistent with this account is the fact that targets which are stabilized on the retina are more likely to be induced to disappearance than the ones moving across the retina.
[edit] Implications
MIB reveals that the brain uses mental models in order to process reality. The phenomenon also enables researchers to study consciousness, and attention with objective methods.[12]
As the phenomenon was discovered so recently, researchers have speculated about whether MIB occurs outside the laboratory, without being noticed as such. Situations such as driving, in which some night drivers should see stationary red tail lights of the preceding cars disappear temporally when they attend to the moving stream of lights from oncoming traffic may be case points.[13]
[edit] See also
[edit] References
- ^ Bonneh, Y. S., Carmel, M., Donner, T. H., Fried, M., Cooperman, A., Heeger, D. J., & Arieli, A. (2010). Motion-induced blindness and microsaccades : Cause and effect. Journal of Vision, 10, 1-15.
- ^ Ramachandran, V. S., & Gregory, R. L. (1991). Perceptual filling in of artificially induced scotomas in human vision. Nature, 350, 699-702.
- ^ Bonneh, Y. S., Cooperman, A., & Sagi, D. (2001). Motion-induced blindness in normal observers. Nature, 411, 798-801.
- ^ Porta, J. B. (1593). De refractione. Optices parte. Libri novem. Naples: Salviani.
- ^ Breese, B. B. (1899). On inhibition. Psychological Monographs, 3, 1-65.
- ^ Graf, E. W., Adams, W. J., & Lages, M. (2002) Modulating motion-induced blindness with depth ordering and surface completion. Vision Research, 42, 2731–2735.
- ^ Hsu, L., Kramer, P., & Yeh, S. (2010) Monocular depth effects on perceptual fading. Vision Research, 50, 1649–1655.
- ^ Hsu, L., Yeh, S., & Kramer, P. (2004). Linking motion-induced blindness to perceptual filling-in. Vision Research, 44, 2857–2866.
- ^ Wallis, T.S.A., & Arnold, D.H. (2009) Motion-Induced Blindness and Motion Streak Suppression. Current Biology 19, 325–329.
- ^ Donner, T.H., Sagi, D., Bonneh, Y.S., & Heeger, D.J. (2008). Opposite neural signatures of motion-induced blindness in human dorsal and ventral visual cortex. Journal of Neuroscience, 28, 10298–10310.
- ^ New, J.J., & Scholl, B.J. (2008). ‘‘Perceptual scotomas’’: A functional account of motion-induced blindness. Psychological Science, 19, 653–659.
- ^ Koch, Christof (13 June 2007). "The Quest for Consciousness". Roberts & Company Publishers. http://www.questforconsciousness.com/conscious.html. Retrieved 01 December 2011.
- ^ Whitfield, J (14 June 2001). "A brain leaves it out". Nature. http://www.nature.com/news/2001/010614/full/news010614-9.html. Retrieved 01 December 2011.
