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Marcus V. C. Baldo, André M. Cravo; A misconception about the relationship between the flash-lag effect and temporal order judgments. Journal of Vision 2004;4(8):579. doi: 10.1167/4.8.579.
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A prevailing definition of the differential-latency model for the flash-lag effect (FLE) states that a flash takes longer to reach awareness than a continuously moving object. A depthless reasoning leads to the unwarranted conclusion that static and moving objects that are abruptly and simultaneously presented should be perceived with an illusory temporal asynchrony. Ten participants, while keeping their gaze fixated on the center of the monitor's screen, had to perform a temporal order judgment (TOJ) between two abrupt-onset visual stimuli presented at the right and left hemifields in three different combinations (run in three blocked experimental sessions): (i) two moving dots; (ii) two static dots; (iii) a moving dot and a static dot. In another experimental session the combination of moving and static stimuli was able to evoke a significant FLE (74 ± 14 ms, P < 0.01). Yet, significant perceptual asynchronies were not found in the TOJ tasks, even for the combination of moving and static stimuli (PSE = 0.4 ± 4.9 ms, P > 0.93). In our procedure, the observation of a nil perceptual asynchrony between moving and static stimuli is not inconsistent with the presence of a distinct FLE, owing to the appearance of a coexisting perceptual event, namely the Fröhlich effect. The observation of a perceptual simultaneity of moving and static stimuli, in conjunction with a spatial misalignment between them, was also easily obtained from computational simulations of a simple feed-forward neural network. These simulations showed that, depending on the stimulation parameters, temporal effects can be uncoupled from spatial ones. Thus, our results suggest that the FLE emerges from differential perceptual latencies between abrupt-onset and continuous stimuli rather than between flashing and moving objects.
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