May 20, 2009
The Break of the Curveball
When delving into presuppositional arguments (or the Argument from Reason, or other claims by Christians in support of mind-brain dualism), I’ll often point out that the brain we have is not cognitively reliable in precisely the sort of ways you would expect given evolution — e.g., things like Alien Hand Syndrome, optical illusions, and so on.
Thanks to Stephanie, I’ve now found the single best illustration I’ve ever seen of the way in which our brain can be fooled: the break of the curveball in baseball.
Those of us who threw curveballs know the fundamental dilemma: a classic, Blylevenesque “12-to-6” curveball appears to break much more sharply than it actually does. Part of the work of the “break” is accomplished by downward spin, and part of it is accomplished by optical illusion.
If you follow this link, you’ll see the optical illusion portion of the curveball’s break illustrated vividly. Watch the path of the spinning ball, and you can see that it travels in a straight line. Shift your focus to the blue spot, and the ball seems to be curving away from you at a drastic angle. It’s eerie!
The authors conclude:
In baseball, a curveball creates a physical effect and a perceptual puzzle. The physical effect (the curve) arises because the ball’s rotation leads to a deflection in the ball’s path. The perceptual puzzle arises because the deflection is actually gradual but is often perceived as an abrupt change in direction (the break). Our illusions suggest that the perceived “break” may be caused by the transition from the central visual system to the peripheral visual system. Like a curveball, the spinning disks in the illusions appear to abruptly change direction when an observer switches from foveal to peripheral viewing.
Just another datapoint in support of the view that our cognitive faculties are the unreliable, cobbled-together product of millions of years of evolution of the physical brain, and not some disembodied mind crafted by an almighty God.