Vortrag von Lotta Ottensmeyer (GEMI): "Measuring the Duration of an Illusory Motion: Findings from an Adaptive Staircase Procedure"

Wann 09.07.2021
von 13:15 bis 14:45
Wo Online
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In the illusion termed Motion Bridging Effect, a motion, that is not consciously visible, induces a motion percept in a subsequently presented and physically stationary stimulus. Initial investigations of this illusion showed a congruency effect on the direction of this illusory motion and the consciously invisible motion of the preceding stimulus (Mattler & Fendrich, 2010). This congruency effect yields a strong dependency on the interstimulus interval. When a ring of 16 points was rotated at an angular velocity of 1500°/s, the ring appeared as a continuously outlined circle and subjects were generally not able to distinguish between clockwise and counterclockwise rotation. When succeeded by a stationary ring of 16 points of the same size and position, subjects reported the direction of the illusory motion to be consistent with the direction of the leading, rapidly rotating ring. With the function of direction sensitivity forming the shape of an inverted U, this effect is largest in interstimulus intervals of 60 and 90 milliseconds and noticeably reduced in interstimulus intervals of 0 and 180 milliseconds. In a previous study by Mattler, Stein & Fendrich (2021), when subjects were asked to rate the clarity of their motion percept, mean clarity ratings also followed this overall trend. Although widely used, clarity ratings are inherently subjective and possibly based on individual criteria. We attempted to develop a measure for the strength of this illusory movement that does not depend on subjective criteria or the congruency effect alone. In our experiment, we presented an additional visual or acoustic stimulus while the stationary ring was present. Subjects were asked to report the direction of the illusory motion and if they still perceived rotation of the stationary ring when the additional stimulus was presented. Presentation times of this stimulus were manipulated adaptively in a 1up/1down staircase. Estimates of the perceived simultaneity of movement offset and the onset of the comparison stimulus showed a dependency on the interstimulus interval that differed from the overall effect on direction congruency. These findings support the idea that the MBE consists of two processes that potentially influence or enhance each other.

 

Dieser Vortrag findet online statt: https://conf.psych.bio.uni-goettingen.de/b/uma-mf9-zr3
Zugangscode: 113411