Where is the ball? Behavioral and neural responses elicited by a magic trick.

Hugo Caffaratti,Joaquin Navajas,Rodrigo Quian Quiroga,Hernan G Rey

doi:10.1111/psyp.12691

Hugo Caffaratti, Joaquin Navajas + Show 2 more

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We present results from two experiments, in which subjects watched continuous videos of a professional magician repeatedly performing a maneuver in which a ball could "magically" appear under a cup. In all cases, subjects were asked to predict whether the ball would appear under the cup or not, while scalp EEG recordings were performed. Both experiments elicited strong and consistent behavioral and neural responses. In the first experiment, we used two blocks of videos with different probabilities of the ball appearing in the cup and found that, first, based on the behavioral responses, the subjects could track this probability change; and second, the different probabilities modulated the neural responses. In the second experiment, we introduced a control condition in which the magician performed the maneuver under the table, out of subjects' view. Comparing the two conditions (i.e., performing the maneuver within or out of the subjects' view), we found that, first, the magic trick dramatically biased the subjects' behavioral responses; and second, the two conditions led to differential neural responses, in spite of the fact that the stimulus triggering the evoked responses (seeing the ball in the cup) was exactly the same. Altogether, our results show how new insights into sensory and cognitive processing can be obtained using adapted magic tricks. Moreover, the approach of analyzing responses to continuous video presentations offers a more ecological setting compared to classic evoked potential paradigms, which are typically based on presenting static images flashed at the center of the screen.

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It has long been recognized that, from relatively limited, noisy and ambiguous information, perception relies on unconscious inferences based on previous experiences (Helmholtz, 1878a; Helmholtz, 1878b; Gregory, 1973)
Only very few studies have dealt with brain responses elicited by magic tricks, localizing areas that contrasted responses upon different conditions with fMRI recordings (Parris et al, 2009; Danek et al, 2015) It is within this context that we set out to study whether the observation of a magic trick might trigger specific patterns of brain activations, as measured with scalp EEG
Given that subjects were presented videos showing continuous repetitions of the magician performing the trick, this experiment allowed us to characterize brain responses obtained in a much more natural condition compared to the classic evoked potential paradigms implemented by flashing images, which require subjects to keep their fixation at the center of the screen (Luck and Kappenman, 2011; Freeman and Quian Quiroga, 2012)

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It has long been recognized that, from relatively limited, noisy and ambiguous information, perception relies on unconscious inferences based on previous experiences (Helmholtz, 1878a; Helmholtz, 1878b; Gregory, 1973). The scientific interest in magic is not new (Binet and Nichols, 1896; Jastrow, 1897; Triplett, 1900), in the last decades there has been an increasing interest in setting up parallels between magic theory and cognitive neuroscience, in some cases leading to the adaptation of magic tricks into new experimental paradigms (Cui et al, 2011; Rieiro et al, 2013; OteroMillan et al, 2011; Johansson et al, 2005; Kuhn and Land, 2006b; Macknik et al, 2008; Martinez-Conde and Macknik, 2008; Parris et al, 2009; Kuhn and Findlay, 2010; Olson et al, 2012; Shalom et al, 2013; Quian Quiroga, 2016; Lamont and Wiseman, 2005; Kuhn et al, 2014) Most of these experiments have focused on the subjects’ behavioral and oculomotor responses while subjects watched magic tricks. Given that subjects were presented videos showing continuous repetitions of the magician performing (or not) the trick, this experiment allowed us to characterize brain responses obtained in a much more natural condition compared to the classic evoked potential paradigms implemented by flashing images, which require subjects to keep their fixation at the center of the screen (Luck and Kappenman, 2011; Freeman and Quian Quiroga, 2012)

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