Cognitive Daily

What happens to the ball?

Watch this video and describe what you see (it’s a Windows Media file, so if you’ve got a Mac, you’ll need Flip4Mac):

What happened to the ball? Just watch the movie once, then give your response in the poll:

This movie is one of the stimuli for an experiment by Gustav Kuhn and Michael Land, which tries to understand why we are fooled by magic tricks. Because the magician looks up, many viewers are led to believe that he threw the ball off screen. In fact, he palms the ball. In a second video, he looks at his hand instead of up in the air.

In both cases, some people who saw the video claimed they perceived the ball flying off the top of the screen after the fake throw, based on their answers to a questionnaire, the researchers report in the November 21 Current Biology. Participants were nearly twice as likely to experience the illusion when Kuhn looked up on the last throw than when he looked at his hand. “That tells us it’s due to expectations,” Kuhn explains. His gaze was crucial in causing the illusion because it cued the expectations of the watchers, he says.

Participants’ eyes, in contrast, apparently were not fooled. The researchers tracked the gazes of those viewing the videos: during the first two throws viewers’ eyes followed the ball to the top of the screen, whereas on the fake throw their eyes were fixated primarily on Kuhn’s face.

A criticism of the study expressed in the article is that only half of participants ever saw the illusion. When I watched the movie, I thought the trick was so obvious that I couldn’t imagine anyone seeing it, so that’s why I created the poll. Soon, we’ll have a good idea of how many CogDaily readers can see it.

To me, however, whether or not the observers were fooled by the trick, it’s still fascinating that their eyes moved to the juggler’s face when he palmed the ball.

In other news:


  1. #1 Caledonian
    November 21, 2006

    My feeling is that his hand doesn’t move upwards quickly enough to bring the ball to the speed it would have to have for it to be difficult to see leaving the screen. The impulse just isn’t great enough.

  2. #2 Deacon
    November 21, 2006

    In a way, asking where the ball is isn’t a fair question. It’s a magic trick, so people expect the ball to still be in the magician’s hand, regardless of what they see. They’re expecting a trick.

    My first thought when viewing the video is that he could’ve thrown the ball up out of the frame, either into a net or into the hands of somone on a ladder, or something similar to that.

    The only thing I thought was unusual about the trick is that I could’ve sworn that I saw the man’s empty right palm. When I replayed the video after voting, I realized that you never actually see his right palm after the last upwards throw.

  3. #3 Katherine
    November 21, 2006

    The illusion definitely worked on me, but as soon as I saw the poll I realized that the answer would have to be that he still had the ball in his hand. I answered honestly (that I thought he had thrown the ball), but I bet some people who were maybe on the fence about it when they saw the video were tipped off by the question and said that the ball was still in the juggler’s hand.

  4. #4 outeast
    November 21, 2006

    I can’t see the poll, but I never thought he threw the ball – though my eyes flicked up where it would have gone anyway.

    To me more interesting is that I thought he had dropped the ball rather than palmed it – and only figured it out correctly after a third viewing. I spotted the trick, but had the wrong explanation.

  5. #5 Joshua
    November 21, 2006

    Part of the reason people may end up looking at his face is because on the fake throw, his hand ends up almost directly below his face, and as we’re expecting the ball to go up from the hand, our eyes move up. They stop, or at least pause, at the face and notice the expression when we do not see the motion of the ball. In addition, notice the way his fingers point directly at the face after the last throw while he is looking up. Assuming this is an experienced magician, he probably does this on purpose in order to help complete the illusion.

    One give-away (besides the leading question “Where did the ball go?”) is the difference in thumb position in his hand as he flares them, and the fact that the video even stops at that frame allowing us to further examine it. I bet the video would be more convincing if it continued to where his hands were behind his back or similarly.

    On a related note, one of my favorite card tricks involving much sleight of hand is here:
    Amazing trick. I actually taught myself how to do this trick from this video, and it really freaked out my wife when she saw me practicing it. 🙂

  6. #6 julian
    November 21, 2006

    “The only thing I thought was unusual about the trick is that I could’ve sworn that I saw the man’s empty right palm. When I replayed the video after voting, I realized that you never actually see his right palm after the last upwards throw.”

    Same thing happened to me. I really thought I saw his palm but then on a second viewing noticed that you never even see the thumb, let alone the palm.

  7. #7 Miguelito
    November 21, 2006

    My goalie instincts came into play. I kept my eye on the ball and ignored the face (eyes on the puck and the hands, not on the face of the shooter) and knew that the ball never left the guy’s hand.

  8. #8 Saboma
    November 22, 2006

    I also focused on the red ball instead of allowing a widened periphery and saw immediately that the red ball is clutched between the fellow’s thumb and the area beneath the fellow’s thumb. If one looks closely, the fellow’s thumb looks as if it is a bit deformed and almost clawlike.

    It’s a neat illusion.

    Thanks for sharing. ~:o)

  9. #9 Chris
    November 22, 2006

    I use this trick all the time with my son. He’s still convinced that it’s magic.

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