Toads spring right-handed surprise

Toads are right-handed, according to a team of Italian and Australian biologists.

In today's issue of the scientific journal Nature, Giorgio Vallortigara of Udine University in Italy and his colleagues report that when common toads are forced to use their front paws to remove something from their face, they are much more likely to use their right paw than their left.

Apart from a very few naturally ambidextrous people, human beings show a distinct "handedness". Most prefer to use their right hands for tasks involving delicate manipulation. Left-handers are less common.

Biologists have observed similar handedness in many other animals and "footedness" has even been observed in some birds that use their claws to hold and manipulate objects. But "right-pawedness" among toads has come as a surprise. Biologists had assumed that the preference for one side or the other developed only in these animals that use hands, feet, claws or paws to pick up or hold food.

Although the human preference for one hand or the other clearly has an inborn component, the tendency to favour one hand is then reinforced by continual use of the hands during infancy and childhood, so that one side of the brain comes to dominate in directing movement.

Toads use their paws in only limited ways, so the fact that they have a significant preference suggests that handedness and the changes in the brain that accompany it could have evolved very early in evolutionary history.

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