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Masayoshi Nagai, Allison B. Sekuler, Patrick J. Bennett; Representational momentum with different target's contrast. Journal of Vision 2004;4(8):572. doi: 10.1167/4.8.572.
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© ARVO (1962-2015); The Authors (2016-present)
The judged final position of a moving target is displaced forward (i.e., in the direction it is moving), a phenomenon known as Representational Momentum (RM). Although much is known about the conditions under which RM occurs, we still do not have a complete theory of the mechanisms leading to RM, and the development of such a theory requires a better understanding how RM varies as a function of basic visual attributes. Thus, the present study examined the effect of target contrast on RM. The target was a moving spot (diameter = 0.5 deg) with a luminance of 15 (high-contrast) or 30 (low-contrast) cd/m^2; background luminance was 32 cd/m^2. Observers judged whether the target's final position was to the left or right of a probe presented 250 ms after the target's offset. We measured RM with two different eye-movements conditions: maintained fixation and pursuit eye movements for the target. If RM is driven by visible persistence carried by eye movements(Kerzel, 2000), then pursuit eye movements should produce greater RM with a low contrast target, because low contrast targets cause longer visible persistence (e.g., Castet, Lorenceau, & Bonnet, 1993). Furthermore, no RM should be observed when the eyes are fixated. In the fixation condition, two observers showed substantial RM that depended on contrast (i.e., greater RM at low contrast). Two other observers showed very small RM and no contrast effect. Two of those observers were tested also in the smooth pursuit condition. Both observers exhibited RM, but only one observer showed a clear effect of contrast. The results suggest that RM is not just due to the visible persistence carried by eye movements. First, RM can be obtained when there is no moving, persisting image after target offset. Second, different durations of visible persistence do not modulate the magnitude of RM consistently across observers.
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