16:30 - 18:00
Parallel sessions 3
16:30 - 18:00
Room: HSZ - N5
Chair/s:
Elisabeth Hein
In order to perceive and meaningfully interact with the world around us, our sensory systems need to interpret the incoming information. This interpretation process is well illustrated in the case of illusions. With some illusions we perceive very different things in one and same input, as for example in the famous Necker cube or “The dress”, which can be seen blue and black or white and golden. Other illusions make us perceive colors where there are none, as in the watercolor illusion, or cause-and-effect relationships and animacy with simple dots. Therefore, illusions are a wonderful tool to understand more about how perception works. In the symposium, we will look at this question using a variety of different experimental methods and very different illusions in order to learn more about different aspects of perception ranging from auditory motion perception to robotic vision. In particular, in the first talk Meike Kriegeskorte and colleagues will use auditory apparent motion to investigate which factors influence how object correspondence is established, i.e. object identity is perceived despite changes in location across time. In the second talk Shalila Freitag and colleagues will talk about EEG correlates of perceptual (un-)certainty and the role of stimulus predictability when participants observe stimuli with varying degree of ambiguity/visibility (Necker lattices and smiley faces). In the third talk Ben Sommer and colleagues will investigate perceived causality in a paradigm in which a disc can either be perceived as launching another disc or as passing across the other disc. In particular, they use visual adaptation to look at the influence of a launch or pass context on an ambiguous display. In the fourth talk Vebjørn Ekroll will use examples of magic tricks around the illusion of absence that work better than one would expect based on the method of the trick and how perception works. In the last talk Aravind Rao Battaje and colleagues will present work on whether robotic perceptual models could predict population-level and individual human responses to visual illusions, using the example of the fill-in color aftereffect and Silencing by motion.
Submission 433
Learning About Perception by Studying the Art of Magic
SymposiumTalk-04
Presented by: Vebjørn Ekroll
Vebjørn Ekroll
Department of Psychosocial Science, University of Bergen, Norway
Many magic tricks work much better than one would expect based on knowledge of the secret method and known psychological mechanisms, which suggests that there are unknown psychological factors at play. Thus, a promising heuristic for advancing cognitive science by studying the art of magic is to look for tricks which work much better than expected. As an illustration of the application of this research heuristic, I summarize recent research on the illusion of absence. This phenomenon can be described as the compelling visual impression that the space behind an occluder is empty, even when it is not. The phenomenon is similar to amodal completion in the sense that it refers to occluded scene regions and is cognitively impenetrable, but different from amodal completion in the sense that it cannot be explained in terms of the Gestalt principle of good continuation. This phenomenon contributes to explaining how magicians can create powerful illusions where things seem to appear out of nowhere, vanish into thin air, or levitate with surprisingly simple methods. Interestingly, the same illusion may also contribute to our understanding of road accidents where drivers report that other road users seemed to appear out of nowhere. The currently available evidence suggest that the illusion is more likely to occur (1) with narrow occluders and (2) when the motion paths of the occluder and the occluded objects are accidentally aligned. Overall, the findings are in line with Irvin Rock’s coincidence avoidance principle.

Supported by the Research Council of Norway, project 334817.