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“School of Cognitive Sciences”

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Paper   IPM / Cognitive Sciences / 7494
School of Cognitive Sciences
  Title:   What is the Role of Early Visual System in Fash-Lag Effect?
1.  A. Najafian
2.  M. Sanayei
3.  M. Adibi
4.  B. Noudoost
5.  S. Oveisgharan
6.  A. Gharagazarloo
  Status:   In Proceedings
  Proceeding: The first International Conference of the National Neuroscience of Romania
  Year:  2003
  Supported by:  IPM
Theories of Flash-Lag Effect (FLE) have suggested a variety of mechanisms to explain the level of visual processing responsible for this phenomenon. In this study we separated analysis of static and moving objects to determine the role of successice levels of the visual system involved in FLE. Two subjects performed psychophysical experiments with two tasks. In task 1FP, the subjects aligned two flashes with two bars moving in opposite directions, viewing them on the monitor normally with two eyes. In another task, 2FP, the subjects viewed flashes and moving bars dichoptically preventing the information from flashes and moving bars from being integrated at least at the level of retina. The difference between calculated Flash-Lag Index in1FP and 2FP trials was significant: AN: 1FP lag=39.086 ms, 2FP lag=51.880 ms, P < 0.01; MS: 1FP lag=34.510 ms, 2FP lag=47.570 ms, P<0.001; Our result is in agreement with theories that account for a retinal mechanism of FLE. Our data further suggests that for a unique FLE theory, the mechanism should occur independently in lower levels (retina) and higher levels of visual hierarchy. Thus, Differential Latency and Motion Extrapolation theories could not account for our results, since the first proposes a unique mechanism for FLE and the latter suggests only high-level mechanisms. In Postdiction theory, different internal motion models are possible at every level of motion-processing system; thus a flash can reset these internal models of motion independently.

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