The Secret of the Curve Ball

Ever wondered why its so tricky to hit the curve ball in baseball? Well, this example might just show you why. Big news is that three best visual illusions in the world were chosen last weekend, at a gathering of neuroscientists and psychologists at the Naples Philharmonic Center for the Arts in Florida. We’ve been reporting about the annual competition each year, and this year’s winning submission was created by Arthur Shapiro, a Bucknell University professor.

A properly thrown curve ball spins in a way that makes the air on one side move faster than on the other. This causes the ball to move along a gradual curve. From the point of view of a batter standing on home plate, though, curve balls seem to “break,” or move suddenly in a new direction. This year’s winning illusion may explain this phenomena. Arturo’s animation shows a spinning ball that, when watched directly, moves in a straight line. When seen out of the corner of the eye, however, the spin of the ball fools the brain into thinking that the ball is falling towards the left. We had another VERY SIMILAR example posted few months ago.

So, as a baseball flies towards home plate, the moment when it passes from central to peripheral vision could exaggerate the movement of the ball, causing its gradual curve to be seen as a sudden jerk. Be sure to observe the falling ball directly, and indirectly (from aside) while reading the text embedded inside the animation. See the difference? Other winning illusions will be posted shortly. More can be found here.

34 Replies to “The Secret of the Curve Ball”

  1. Nice illusion, but I think it’s the shadow rotating around the ball that gives this illusion that effect. In baseball, there is not shadow rotating around the ball.

    I’ll bet if the shadow were to rotate the other direction, but still have the same curve, the ball would appear to drop the other direction when viewed with peripherial vision.

  2. Slide the “Speed” control from one end of the scale to the other to get the ball to appear to fall at an opposite angle.

  3. That’s wild!!
    I see that some could think the shadow is causing the effect, but I believe that the stitches on the baseball would have the same effect as the shadow does in this example.

  4. I think Euclids Brother has missed the point – he ball is not curving at all but falling straight down, its only when you look at the dot say and so see the ball in your perifery that it arcs.

  5. Oh my god! This is one of the very very very very few illusions that has made me gasp out loud and shout oh my god!

  6. Wow, this makes total sence, thank you for explaining that. Everyday we learn something new :D. In regards to Euclid’s Brother’s comment, in baseball, we dont see a shadow like that, but the strips on the ball do add just enough difference for the eye to percieve this illusion. Keep posting, I’m a great fan!

  7. This Is My First Comment…

    But I Found That You Can Make It Go Straight Down. If You Look At The Blue Dot Then Put Your Mouse Wherever It Goes Off The Page, Then Put Your Finger Wherever It Comes Back On The Page, And To Me It Makes It Look Like It Is Going Straight Down.


  8. if you use the controls you can change the speed from negative to positive. this gives the same effect of the ball suddenly curving away

  9. If you keep looking at teh blue dot, and drag teh SPEED slider left anbd right, you can get the ball to appear to wobble from side to side in a very convincing manner.
    Sure a baseball doesn’t have the shadow, but it has stitches so the illusion is appropriate.

  10. Something VERY fun to do, is hold the speed slider, look at the blue dot and moderately drag the slider between the left and right. It will appear that the ball is alternating directions back and forth.

  11. Best illusion I have seen in a long time. I think Euclid’s Brother has it sorted. You can reverse the spin by changing the speed parameter from a negative to a positive, and the ball does seem to drift towards the blue dot. Peripheral vision has its value in detecting change and movement. The repetitive change is perceived as movement. Very important (for survival) to know quickly if something is going to cross your path/vision or is moving away from it. The brain is fooled by that data compression of 6m pixel receptor pushing through a 1m neron pathway. Witness reconstructions of events not in direct (attentive) view are now suspect.

  12. To Euclid’s Brother,
    you do realize that you can change the Speed from -12 to 12 right? Therefore making the shadow move the opposite way and making the ball appear to fall in the opposite direction…

  13. This has nothing to do with baseball. I have thrown a curve-ball all my life and the way it curves is with the way the ball spins. Not by its shadow or something dumb like that.

  14. Its not the blue ball, if you look any where on your
    screen exept the falling ball,will do the same effect,try it.

  15. That’s not how a curveball spins. It’s spinning sideways; curves spin front to back (if that makes sense). As in, 12/6 rotation. Not that sideways shadowing.

  16. This is pure BS. The ball moves on any pitch due to the forces being placed upon it. A knuckleball flutters, dips, and dances due to the lack of spin. Air moves over the seams at different rates causing the movement.

    This is basic physics and aerodynamics.

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