Have you ever wondered if your dog or your cat, but also the parrot, the hamster or the turtle, are right-handed or left-handed? Have you ever observed which paw they use most to play with their ball or to scratch behind their ears? The lateralization, that is the predominance of one part of the body over the other, is in fact a feature common to the whole animal kingdom: it was discovered at the end of the 1970s by Lesley Rogers, researcher at the University of New England (Australia) studying the chickens.
Tell me which hemisphere you use and I'll tell you who you are . But what determines the greater use of a hand, a paw, but also of an eye, a chela or an antenna, compared to the other? It all depends on the spatial organization of the brain: each region is in fact responsible for some specific functions. This means that the predominance of one hemisphere over the other, and therefore of one side of the body over the other, depends on the areas involved from time to time in the various operations. But different individuals can perform the same task with different strategies, thus engaging different areas of the brain: this is why some of us, while writing or playing tennis with the right hand, become left-handed when it comes to kicking a ball. And the same happens among animals. And by observing our furry, feathered or scaled friends we can learn a lot about their behavior and their mood.
Dog: take notice of the direction in which he is swaying. If he furiously moves his tail to the right it means he is happy and well disposed towards anyone who is coming against him. If the tail moves mainly towards the left, it means that Fido feels uncomfortable and could retreat or show an aggressive reaction. An Italian study of 2007 highlighted this (Focus.it had talked about it here).
Cat : in cats, lateralization is linked to sex. Deborah Wells and Sara Millsopp, two psychologists at Queen's University in Belfast, have recently discovered that the majority of male cats are right, while females are mostly left-handed. Do you want to make sure? Give your kitty a jar with its favorite morsel in it and observe with which paw it tries to extract its contents.
Birds and rodents: parrots, canaries, hamsters and mice use the dominant paw to bring everything they find interesting to the mouth or nostrils.
Pisces: even the goldfish can be right-handed or left-handed. Try to put an object unknown to him in the center of his tank and see if he swims around in a clockwise or counterclockwise direction. This way you will know what its dominant eye is.
Reptiles: move closer to the side of your snake, if you have one, a clamp with a mouthful of food. Its dominant side will be the one where you will observe the quickest and most ready reaction to jelly. All the studies conducted to date agree that reptiles are mainly right-handed.
Horse : most horses have been trained for centuries to be governed starting from the left side. And indeed all the most recent research has confirmed that in the equines the left eye is the most used to keep under control what happens in the immediate vicinity. And even the reactions to any perceived dangers with this eye are much more readily available and faster than those recorded with the right eye.
Better the right or the left? But is there an evolutionary advantage in being right-handed or left-handed? According to some studies, no: frogs know it very well, the sight of which is usually more acute from the left eye, exposes them to attacks by snakes and other predators from the right. But then why hasn't this feature been lost over time and we animals have not all become perfectly ambidextrous? Other studies instead attribute to the lateralization an advantage in terms of speed of information processing, especially in animals such as fish and birds that have eyes on the sides of the head and that in this way can process the messages from the two separately and in a shorter time eyes.
Watch out for lefties . And in man? Numerous studies have shown that left-handed people have an advantage in sports where there is a direct comparison, for example tennis or boxing. Charlotte Faurie and Michel Raymond The University of Montpellier, France, studied eight non-industrialized societies that still live in a primitive state and noted that those with the greatest number of killers also count the largest number of left-handed people. This could indicate that left-handers have an advantage in hand-to-hand combat and therefore more often come out winners.