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“School of Cognitive Sciences”

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Paper   IPM / Cognitive Sciences / 7492
School of Cognitive Sciences
  Title:   Invisibility patterns of unresolvable Gabor patches in motion induced blindness
  Author(s):  R. Rajimehr
  Status:   In Proceedings
  Proceeding: IBRO
  Year:  2003
  Supported by:  IPM
Motion Induced Blindness (MIB) is observed with normal-sighted observers when a global moving pattern is superimposed on a target Gabor patch. It has been shown that MIB for two adjacent Gabor patches occurs simultaneously when they are collinear and independently when they are orthogonal. Rivalry and co-operation among orientation signals can be a possible mechanism for this effect. In 3 experiments, patterns of invisibility in MIB were studied using Gabor patches with spatial frequencies beyond the perceptual resolution limit. The first experiment demonstrated that the mean duration of simultaneous blindness for two collinear unresolvable Gabor patches was not significantly longer compared to orthogonal ones. It could be argued that interactions (rivalry and co-operation) among orientation signals of Gabor stimuli occur only when there is high performance in orientation discrimination. An unresolvable Gabor stimulus was seen as a uniform patch lighter (desaturated) relative to the background. In the second experiment, the simultaneous blindness period was measured for two adjacent physically uniform patches in comparison to a physically uniform patch presented adjacent to a perceptually uniform one (i.e. unresolvable Gabor patch). Results showed that the mean duration of simultaneous blindness for the physically uniform pair was significantly longer than mixed pair. This experiment demonstrates interactions between orientation and luminance attributes of unresolvable Gabor patches. In the third experiment, one Gabor patch (either resolvable or unresolvable) was presented as a target in the MIB paradigm. Target orientation change was detected in the resolvable target condition but was at chance level in the unresolvable one; however, abrupt change in orientation during the disappearance phase of MIB popped out in both conditions and the target reappeared rapidly. These results are consistent with the evidence implying change detection without awareness.

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