What butterfly wings have in common with barbershop poles

Old-fashioned striped barbershop poles turn in place on a vertical axis, but humans typically perceive the stripes moving upward rather than turning with the pole. It's a well-known visual illusion arising from processing biases in human vision. According to a new paper published in the journal Nature, a similar effect could explain how butterflies often evade predatory birds: Their flight patterns and wing patterns combine to make it hard for predators to accurately gauge speed and direction.