An fMRI investigation of expectation violation in magic tricks

Abstract

Magic tricks violate the expected causal relationships that form an implicit belief system about what is possible in the world around us. Observing a magic effect seemingly invalidates our implicit assumptions about what action causes which outcome. We aimed at identifying the neural correlates of such expectation violations by contrasting 24 video clips of magic tricks with 24 control clips in which the expected action-outcome relationship is upheld. Using fMRI, we measured the brain activity of 25 normal volunteers while they watched the clips in the scanner. Additionally, we measured the professional magician who had performed the magic tricks under the assumption that, in contrast to naïve observers, the magician himself would not perceive his own magic tricks as an expectation violation. As the main effect of magic - control clips in the normal sample, we found higher activity for magic in the head of the caudate nucleus (CN) bilaterally, the left inferior frontal gyrus and the left anterior insula. As expected, the magician's brain activity substantially differed from these results, with mainly parietal areas (supramarginal gyrus bilaterally) activated, supporting our hypothesis that he did not experience any expectation violation. These findings are in accordance with previous research that has implicated the head of the CN in processing changes in the contingency between action and outcome, even in the absence of reward or feedback.

Keywords: action; caudate nucleus; expectation violation; fMRI; magic; movement observation; perceptual prediction error.

FIGURE 1

Standardized setting shortly before the magic trick (here: Rubik’s Cube) is performed.

FIGURE 2

Procedure of one block including color task.

FIGURE 3

Brain activity at the moment of expectation violation for magic tricks compared to control clips, independent of presentation order (main effect, p < 0.001 uncorrected, voxel cluster threshold 30). The discrete time point of magic was determined by an independent group of subjects (see Materials and Methods). The color bar depicts the t-values of the supra-threshold voxels. Activations are overlaid on the normalized average structural image from all subjects tested, values represent z-values in Montreal Neurological Institute (MNI)-coordinates.

FIGURE 4

Brain activity for entire clip duration for the contrast magic – control (main effect, p < 0.001 uncorrected, voxel cluster threshold 30). The color bar depicts the t-values of the supra-threshold voxels. Activations are overlaid on the normalized average structural image from all subjects tested, values represent z-values in MNI-coordinates.

FIGURE 5

Magician Thomas Fraps: significant activity for magic vs. control condition showing sensory-motor and parietal activity in the magician. The color bar depicts the t-values of the supra-threshold voxels. Activations are overlaid on the normalized structural image from the magician tested, values represent z-values in MNI-coordinates.