Flash lag illusion
The flash lag illusion or flash-lag effect is a
Motion extrapolation
The first proposed explanation for the flash-lag effect is that the visual system is predictive, accounting for neural delays by extrapolating the trajectory of a moving stimulus into the future.[2][4] In other words, when light from a moving object hits the retina, a certain amount of time is required before the object is perceived. In that time, the object has moved to a new location in the world. The motion extrapolation hypothesis asserts that the visual system will take care of such delays by extrapolating the position of moving objects forward in time.
Latency difference
A second proposed explanation is that the visual system processes moving objects more quickly than flashed objects. This latency-difference hypothesis asserts that by the time the flashed object is processed, the moving object has already moved to a new position.[5][6] The latency-difference proposal tacitly rests on the assumption that awareness (what the subject reports) is an on-line phenomenon, coming about as soon as a stimulus reaches its "perceptual end-point".[7]
Motion integration and postdiction
A recent study tries to reconcile these different approaches by approaching perception as an inference mechanism aiming at describing what is happening at the present time.[17] In particular, it could extend the motion extrapolation hypothesis by weighting this prediction by the precision of the current information. Thus, the corrected position of the moving target is calculated by combining the sensory flux with the internal representation of the trajectory, both of which exist in the form of probability distributions. To manipulate the trajectory is to change the precision and therefore the relative weight of these two information when they are optimally combined in order to know where an object is at the present time. For an object that moves predictably, the neural network can infer its most probable position taking into account this processing time. For the flash, however, this prediction can not be established because its appearance is unpredictable. Thus, while the two targets are aligned on the retina at the time of the flash, the position of the moving object is anticipated by the brain to compensate for the processing time: it is this differentiated treatment that causes the flash-lag effect. Moreover, this could also explain related phenomena such as motion reversal.[18]
See also
- Tau effect
- Kappa effect
- Cutaneous rabbit illusion
- Temporal illusions
- Fröhlich effect
References
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Other references
- Baldo, M.V.; Klein, S.A. (1995). "Extrapolation or attention shift?". S2CID 4306779.
- Snowden, R.J.; Braddick, O.J. (1989). "The combination of motion signals over time". Vision Research. 29 (11): 1621–30. S2CID 6015282.
- Snowden, R.J.; Braddick, O.J. (1991). "The temporal integration and resolution of velocity signals". Vision Research. 31 (5): 907–14. S2CID 16996397.