May 20, 2009

The Break of the Curveball

Posted in Baseball, Law, Science, Worldview tagged , , , , at 12:34 pm by Andrew

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.


  1. Nathaniel said,

    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.


    Does Christianity entail that we are never subject to perceptual illusions?

    Does it entail that our cognitive powers are unrelated to the physical structures of our brains?

    The break of the curveball is cool, but this is completely irrelevant to the evaluation of Christianity.

    • Andrew said,

      If this doesn’t strike you as pretty good evidence against dualism, I submit that you’re not really open on the subject. And that’s fine, I guess, but it’s kind of weird to say that the way our brains work is “completely irrelevant” to the evaluation of Christianity.

  2. Nathaniel said,


    If this strikes you as evidence against interactive mind-body dualism, I submit that you never really understood the position in the first place. Don’t feel bad. You have a great deal of company.

    I didn’t say that “the way our brains work is completely irrelevant to the evaluation of Christianity” — those are your words, not mine. But you can use a fact about the way out brains work as evidence against Christianity only if that fact is more to be expected if Christianity is false than it is if Christianity is true. There is nothing in your post to suggest that this is true regarding our perception of the break of the curveball.

    • Andrew said,


      Rather than glibly assert that I don’t understand the argument, why don’t you present it?

  3. Nathaniel said,


    I never said that you don’t understand the argument, as you will see if you read what I wrote more carefully. I suggested that, if you think that perceptual illusions are an argument against interactive mind-body dualism, then you do not understand that position.

    Did you want references to the work of W. D. Hart, Richard Swinburne, John Hawthorne, and Charles Taliaferro?

  4. Antiplastic said,

    The dualism angle is a bit of a red herring. Perceptual and cognitive illusions absolutely present challenges to the AfR or any variant argument that insists that intelligence was the product of intelligent design, even if you think that human intelligence is a purely material phenomenon.

    It is a simple dysteleological argument. Human consciousness operates with all the kludged-in complexities, the pointless jury-rigging, the good-enough-for-government-work satisficing solutions you would expect any other biological system to have if it were the product of evolution. But if you are going to look at the actual facts of how actual consciousness actually operates, then you’re stuck with the “Magic Apple Theory of Women’s Pelvises” to explain why Yahweh keeps the assembly line going with all these deficiencies.

    To explain something means to explain why it’s one way instead of another way. But i have never seen a proponent of mind-creationism even lift a finger to go about coming up with an explanation for why we are subject to the cognitive biases and perceptual illusions we are. They seem to have an absolute allergy to facts.

  5. Conrad Coutinho said,

    Most sophisticated Christians argue that any “bad” design (such as misperception) is the result of the historical or symbolic (i guess?) “fall” of man.

  6. Optical illusions aren’t a great example to back up the point being made because Lewis (or rather a Lewis stand-in) can say that that’s not part of how you reason but rather just sensory processing. Better examples are the fact that our abilities which are unambiguously reasoning facilities fail frequently. We’ve all mis-added numbers. And people engage in illogical arguments and fallacies all the time. Even professional mathematicians sometimes make subtle errors in logic.

    The argument from reason fails because we know that our cognition is imperfect already. Indeed, if one is in a snarky mood one can turn the argument around as an argument against the existence of God. If one takes as a premise (as the argument from reason generally seems to) that if there is a God he would create us as perfect reasoning machines then the failures of human cognition suggests that there isn’t a God. So the argument seems to backfire. I don’t think however that anyone thinks about this matter for more than a few minutes and has a background in the sciences would ever try to make a serious argument that the existence of God renders human logic infallible. Lewis’s problem as often is the case with Lewis (I may write a blog post on this later) is that he suffers massively from the C.P. Snow problem. He thinks in a very limited form of how a humanities oriented person thinks and has a view of science that is thus an extreme caricature.

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