Our results indicate that curvilinear motion is a more powerful source of misdirection than rectilinear motion, as used in a classical sleight of hand trick. Particularly, the use of curvilinear motion in the simulated maneuver at the core of the French Drop sleight prevented observers from looking back at the hand that actually retained the coin – after the magician revealed that the hand that had appeared to take the coin was empty (Figure ). To our knowledge, this is the first observation by a non-scientist member of the magic community to have led to a previously unknown, neuroscientific discovery.
Our data moreover show that the differences in the observers’ gaze position at the end of each trial are strongly dependent on the presence or absence or pursuit eye movements during the viewing of the sleight, with curvilinear trials typically generating pursuit eye movements more often than rectilinear trials (Figure ). This suggests a differential engagement of the smooth pursuit and saccadic systems in the dynamic control of attentional focus.
Previous work has investigated the magicians’ use of social misdirection cues, such as their own gaze direction, to manipulate the audience’s eye position (Kuhn and Tatler, 2005
; Kuhn and Land, 2006
; Kuhn et al., 2008a
; Kuhn and Findlay, 2010
; Cui et al., 2011
). Here we show for the first time that different types of hand motion, as used by magicians, can have differential effects on the oculomotor behavior of observers.
Curvilinear target motions may be more salient intrinsically than linear target motions (in addition to the two types of motion affecting differentially the oculomotor system) (Kristjánsson and Tse, 2001
). In the spatial domain, the curves and the corners of object surfaces are perceptually more salient and generate stronger neural activity than straight edges, possibly owing to the fact that they are less redundant and predictable, and therefore more informative (Troncoso et al., 2005
). The same redundancy reduction argument might apply to non-predictable object-motion trajectories, such as curvilinear versus straight motion. If this is the case, curvilinear motion trajectories should be more salient (and consequently engage stronger attention) than straight trajectories.
The capacity of curvilinear movement to misdirect the gaze and/or the attention of observers along a motion trajectory may have far reaching implications outside of magic and pickpocketing, such as in the application of predator-evasion strategies in the natural world, in military tactics, in sports misdirection, and in marketing. Our results demonstrate that magic theory can provide new windows into the psychological and neural principles of perception and cognition.