MASSIMO GIRELLI¹ (); ¹University of Verona, Dept. Neuroscience, Section of Psychology

The orientation of a moving object with respect to its motion trajectory is of fundamental importance for visual perception: It facilitates the predictions about the fate of the object we need to interact with and it mimics the multiple stimulation along the collinear axis to form borders. In the Beta motion, by manipulating the spatial gap between consecutive positions, it is possible to observe the K-effect i.e. The time of a larger gap appears to be prolonged with respect to the actual time. In the first experiment I manipulated the orientation of the elements leading to the Beta motion i.e. orthogonal or collinear with respect to the motion trajectory in a three step sequence with spatially different gaps to get the K-effect. The results from 7 observers showed that the collinear motion led to a significantly smaller K-effect in the final gap of the sequence, on average, up to 41% with respect to the orthogonal motion thus the collinear motion fills the gaps of the Beta motion. In the second experiment, the modulation of the motion extrapolation of moving elements with respect to static ones as in the Flash-Lag-Effect (FLE), was tested with orthogonal and collinear moving elements. Contrary to what it was observed in the K-effect, the collinear moving elements strengthened the FLE. In 15 observers the illusory gap between the collinear motion and the static flash was 61% larger with respect to the orthogonal motion. Thus, collinear motion better provides evidence of predictive activation along motion trajectory. All in all, objects moving collinearly to their motion trajectory embodies better the prediction of their future positions in space as in an anticipatory jet contrail that overlaps the motion trajectory.