“Handedness is a form of hemispheric asymmetry, meaning the dominance of one side of the brain for certain activities,” Ocklenburg says. It is influenced by genetic and environmental factors and also applies to animals, he says.
Many animal species show a left-right preference, he adds.
Together with biopsychologists Felix Ströckens and Onur Güntürkün, Ocklenburg analysed 119 animal species in a study that spanned pawiness in cats, claw preferences in parrots and handedness in monkeys. The study also looked at amphibians, fish and reptiles.
In around a third of the species, the animals showed no clear preference for one side over the other.
But in most species, animals favour one side, including a whole series of animals that prefer to perform tasks with their left limb, just as, generally, humans tend to be right-handed.
“These results make it clear that limb preferences are the rule and not the exception in the animal kingdom,” Ocklenburg says in another study.
Further investigations have focused on pets, with a meta-analysis showing more than three quarters of the cats studied were either right-pawed or left-pawed. Around one in four cats used both paws equally often.
Scientists saw a similar pattern in dogs, with more than two-thirds favouring either the left or the right paw.
Animals that do not have arms or legs in the classic sense may also show a preference, or handedness, says Ocklenburg.
A team led by environmental scientist Annette Sieg from the University of Michigan, for example, says leatherback turtles show a preference for the right. Females of this turtle species often use their right rear flipper to cover their eggs when laying them, for example.
Even invertebrates with simple nervous systems can show limb preferences, including the gazami crab, a type of swimming crab that is widely fished and eaten in East Asia.
When seeking food, it opens mussels more often with its right claw than with its left claw, according to a study published in The Biological Bulletin.
If you think only animals with two front limbs show a clear side preference, think again. Even eight-armed creatures such as octopuses have a favourite arm to reach for certain foods, according to an older study by the Konrad Lorenz Institute for Evolution and Cognition Research in Austria.
Just like humans, many animal species are more skilful with one of their limbs. Pet owners can use simple tricks to find out for themselves which paw their four-legged friend prefers.
“In principle, most people do it with ‘food reaching’ tasks,” says Ocklenburg. These are tasks in which the animal has to reach for food, so you might hide a treat in a tube so narrow that only one paw can fit through it.
“If your pet uses the same paw several times in succession to reach the food, then you know that the animal is right- or left-footed,” he says.