'Cups and Balls' is a classic illusion performed by Roman magicians as far back as 2,000 years ago. The trick provides neuroscientists with a tool to test the building blocks of conscious experience.
The trick has many variations, but the most common one uses three balls and three cups. The magician makes the balls pass through the bottom of cups, jump from cup to cup, disappear from a cup and turn up elsewhere, turn into other objects, and so on. The cups are usually opaque and the balls brightly colored.
Penn & Teller, famous magician duo, helped researches study how even though audiences could see the balls being moved around in transparent cups, the magician's sleight-of-hand misdirected the attention so much that the mind was still fooled. The researchers set out to investigate the hypothesis that the falling ball generated a stronger misdirection of the attention than alternative manipulations.
"Our previous experiments were about discovering new things in science using magic," said Dr. Stephen Macknik, director of the Laboratory of Behavioral Neurophysiology at the Barrow Neurological Institute(BNI). "This was the first study that we did that was specifically for studying something important about magic using science."
Researchers measured the perceptual performance and gaze behavior of naive observers as Teller surreptitiously introduced balls inside opaque and transparent upside down plastic cups. Contrary to the magician’s intuition, a gravity-driven drop of a ball into his hand (or to the floor) caused less misdirection, both in terms of gaze displacement and impaired perception, than alternative manipulations such as lifting the ball, or attempting to drop a ball that is stuck to the cup. Thus, perception of (the effects of gravity on) falling objects does not enhance magic misdirection, at least in the performance of this particular sleight-of-hand trick.
The researchers hope to discover more about joint attention, which is the way we pay attention to other people and objects by means of eye-gazing, pointing or other verbal or non-verbal signals. It's known that people with some conditions, including autism, have a deficit in maintaining this kind of attention.
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