Imagining your tennis serve or mentally running through an upcoming speech might help you perform better, studies have shown, but the reasons why have been unclear. A common theory is that mental imagery activates some of the same neural pathways involved in the actual experience, and a recent study in Psychological Science lends support to that idea.
Scientists at the University of Oslo conducted five experiments investigating whether eye pupils adjust to imagined light as they do to real light, in an attempt to see whether mental imagery can trigger automatic neural processes such as pupil dilation. Using infrared eye-tracking technology, they measured the diameter of participants' pupils as they viewed shapes of varying brightness and as they imagined the shapes they viewed or visualized a sunny sky or a dark room.
In response to imagined light, pupils constricted 87 percent as much as they did during actual viewing, on average; in response to imagined darkness, pupils dilated to 56 percent of their size during real perception. Two other experiments ruled out the possibility that participants were able to adjust their pupil size at will or that pupils were changing in response to mental effort, which can cause dilation.
The finding helps to explain why imagined rehearsals can improve your game. The mental picture activates and strengthens the very neural circuits—even subconscious ones that control automated processes like pupil dilation—that you will need to recruit when it is time to perform.