- Left-footed - Animals Have a Favourite Side
Left-handedness presents various challenges in everyday life. But does this only apply to humans? Recent research suggests that animals may also have a preferred paw or flipper - even down to an octopus' favorite arm.
Handedness was once considered an exclusively human phenomenon. Therefore, the 13th of August has been dedicated to left-handers worldwide since the 1990s. This includes roughly one in ten people, according to an international study presented in 2021. Biopsychologist Sebastian Ocklenburg from the Medical School Hamburg contributed to this study and has much to say about animals as well.
Many animals have a dominant paw
"Handedness is a form of hemispheric asymmetry, meaning dominance of one brain hemisphere for certain activities," Ocklenburg explains to the German Press Agency. This is influenced by both genetic and environmental factors, which also applies to animals. Many animal species exhibit a left-right preference, he adds.
Together with biopsychologists Felix Ströckens and Onur Güntürkün, Ocklenburg analyzed 119 different animal species in a study: from paw preference in cats to claw preference in parrots to handedness in apes. They also looked at amphibians, fish, and reptiles. The researchers found that in about one-third of the species, the animals did not show a clear preference for one side.
However, most species preferred a certain side. Among them were many animals that preferred to use their left side - similar to how humans tend to be right-handed overall. "These results show that limb preferences are the rule, not the exception, in the animal kingdom," Ocklenburg writes in another study.
Further studies focused on pets. A meta-analysis showed that more than three-quarters of the cats examined were either right-pawed or left-pawed. About one in four cats used both paws equally frequently. A similar pattern was observed in dogs: more than two-thirds preferred either the left or right paw.
Side preference in animals with fins
Interestingly, animals that don't have arms or legs in the classical sense may also exhibit a form of handedness, Ocklenburg reports. A team led by environmental scientist Annette Sieg from the University of Michigan observed leatherback turtles in a study and found a preference for the right side. This means that the females of this turtle species often used their right hind flipper to cover their eggs while laying them.
Even invertebrates with simple nervous systems can show limb preferences. In a study published in "The Biological Bulletin," researchers observed the Gazami crab, a type of swimming crab commonly caught and eaten in East Asia. The result: when searching for food, it often opens mussels with its right claw more than its left.
One might think that only animals with two front limbs show a clear side preference. Not so: An older study by the Konrad Lorenz Institute for Evolution and Cognition Research in Austria found that even eight-armed creatures like squid have a favorite arm for reaching for certain food.
Experiments with pets
Like humans, many animal species are more skilled with one of their limbs. Pet owners can easily find out which paw their four-legged friend prefers using simple tricks.
"In principle, most people approach 'food reaching' tasks the same way," explains biopsychologist Ocklenburg. These are tasks where an animal has to reach for food. For instance, a treat can be hidden in a tube so narrow that only one paw fits through. "If the animal uses the same paw repeatedly to get the food, we know: the animal is right- or left-pawed," says the researcher.
Sebastian Ocklenburg - Left-handedness and brain asymmetries study - Ströckens/Güntürkün/Ocklenburg: Limb preferences in non-human vertebrates - Website World Left-Handedness Day - Population level "flipperedness" in the eastern Pacific leatherback turtle study - Ocklenburg/Isparta: Paw preferences in cats and dogs: Meta-analysis - Ontogeny of Cheliped Laterality and Mechanisms of Reversal of Handedness in the Durophagous Gazami Crab study - Byrne/Kuba - Does Octopus vulgaris have preferred arms? - Papadatou-Pastou/Ntolka/Ocklenburg - Human handedness: A meta-analysis.
In the animal kingdom, even species without traditional limbs demonstrate a form of handedness. For instance, research on leatherback turtles has shown a preference for the right hind flipper among females when laying eggs. (Reference: Side preference in animals with fins)
In his study with biopsychologists Felix Ströckens and Onur Güntürkün, Ocklenburg analyzed the limb preferences of 119 different animal species, including Germany's domestic cats and dogs, revealing a dominant side preference in the majority of these species. (Reference: Many animals have a dominant paw)
