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Overwhelmingly, the sighted individuals succumbed to what is known as the “size-weight illusion.”

"The sighted group, where each member was able to see how big each box was, overwhelmingly succumbed to the 'size-weight illusion' and experienced the smaller box as feeling a lot heavier than the largest one," Buckingham said.

In effect, the size-weight illusion was nudging the subjects to increase the weight of the projectile they chose — theoretically maximizing its deadliness.

Bingham has been studying throwing ability for more than 20 years, and his work has always been made more challenging by a trick of human perception known as the size-weight illusion.

Researchers have never established exactly what's behind the size-weight illusion, but one possibility is the simple matter of expectations.