Thursday, 10 April 2008

Magic trick reveals gaze direction and attention are not always linked

When magicians trick people using sleight of hand, you'd think it was all about misdirecting where the audience - specifically their eyes - are looking, hence the aphorism: "the hand is quicker than the eye."

But now psychologists in Durham and Dundee have shown that it's not so much where the audience's gaze is directed that is important, but rather where they are focusing their attention. That's right, the two things are not necessarily the same.

Most of the time we pay attention to where we're looking, but we don't have to. For example, we can, if we want, stare straight ahead while focusing our attention to the side.

Gustav Kuhn and colleagues played university students a clip of a short magic trick in which the magician appears to make a cigarette and lighter disappear. The cigarette "disappears" when the magician drops it into his lap while directing the audience's attention to his other hand.

Surprisingly, recordings of the students' eye movements showed that whether or not they spotted the cigarette drop (and hence realised how the trick was done) had nothing to do with their eye position at the moment of the drop. Blinks or eye movements during the drop were also irrelevant.

By contrast, the students' eye position after the cigarette drop was associated with whether they saw it. Specifically, those students who, after the drop, moved their eyes more quickly to the (now empty) cigarette hand, were more likely to report having seen the cigarette fall.

The likely explanation is that those students who, post drop, made the faster glance to the cigarette hand had already shifted their attentional spotlight (but not yet their eyes) to the cigarette, in time to see it drop. This would be consistent with previous research showing that our eye movements to a given location are preceded by an attentional shift to that same spot. This means that for the trick to work, the magician needs to misdirect the audience's covert attentional spotlight, not necessarily their overt eye position.

There's a final complication. Several of the students who spotted the dropped cigarette actually moved their eyes to the magician's face before his cigarette hand. They still glanced, post drop, to the cigarette hand faster than the students who didn't see the drop, but they looked at the face first. However, this is still consistent with our explanation. It merely suggests, in line with previous research, that the attentional spotlight can be two or more locations ahead of where the eyes have yet to move.

Link to magic trick.
Link to earlier related Digest item.
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Kuhn, G., Tatler, B., Findlay, J., Cole, G. (2008). Misdirection in magic: Implications for the relationship between eye gaze and attention. Visual Cognition, 16(2), 391-405. DOI: 10.1080/13506280701479750

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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