7 Surprising Facts About Left-Handedness in Animals
Left-handedness in animals might be more common than you think.
Posted May 31, 2020 | Reviewed by Gary Drevitch
About 10.6% of humans are left-handed (Papadatou-Pastou et al., 2020) – but what about animals? Here are 7 surprising facts about the science of left-handedness in animals.
- Initially, scientists thought only humans can be left-handers. Not too long ago, scientists thought that left- and right-handedness was something that was typical for humans but could not be observed in animals. They thought this because only humans conduct fine motor tasks like writing for which we show the strongest preference to use one hand over the other. However, recent research has shown that this is not the case, and that many animal species show handedness or, more accurately, limb preferences (Ströckens et al., 2013).
- Today we know that many animal species can show left-handedness. In 2013, a study compared different forms of limb preferences, such as pawedness in cats, foot preferences in birds, and handedness in monkeys across 119 different animal species (Ströckens et al., 2013). The investigated species ranged from toads and lizards to birds and apes. The scientists found that 51% of the investigated species clearly preferred one limb over the other for motor tasks, just as most humans prefer to use their right hand for writing. In 32% of species, individual animals were either left-handed or right-handed, but there was no clear preference for one side on the level of the population. Only in 17% of species was there no evidence of left-handedness. Thus, limb preferences are the rule, not the exception, in the animal kingdom.
- Cats are more likely to be left-handed than humans are. Did you know that left-pawedness in cats is much more common than left-handedness in humans? A recent study that integrated data from many previous studies on pawedness in cats (Ocklenburg et al., 2019) found that when cats were classified into two pawedness categories (left-pawed and right-pawed), 54% were right-pawed and 46% were left-pawed. In studies that used three categories (right-pawed, left-pawed, and no clear preference), 39% of cats were right-pawed, 36% were left-pawed and 25% showed no preference. Thus, left-pawedness in cats is about three to four times as likely to occur as left-handedness in humans. (For more on pawedness in cats, see my detailed post here.)
- Dogs are more likely to be left-handed than humans are. The same study also found a similar pattern for dogs. When dogs were classified into two pawedness categories (left-pawed and right-pawed), 53% were right-pawed and 47% were left-pawed. In studies that used three categories (right-pawed, left-pawed, and no clear preference), 32% of dogs were right-pawed, 31% were left-pawed and 37% showed no preference. Thus, left-pawedness in dogs is about three to four times as likely to occur as left-handedness in humans. (For more on pawedness in dogs, see my detailed post here.)
- Turtles show “flipperedness.” Even animals that do not have hands or paws can show limb preference. For example, a 2010 study of the eastern Pacific leatherback turtle (Sieg et al., 2010) investigated which hindlimb flipper was extended to cover eggs when the turtles were laying eggs. The researchers found that the turtles showed a preference to use their right hindlimb flipper to protect the eggs.
- Even crabs show “clawedness.” While one might think that handedness might only be observed in “higher” organisms with complex nervous systems, that is not true. Handedness can be observed in invertebrates with comparatively simple nervous systems. For example, one study of the Japanese blue crab, a species commonly fished and eaten along the coasts of East Asia, found that the crabs preferred to crack shells with their right claws (Masunari et al., 2020). This shows that even invertebrate species show handedness.
- Octopuses have a favorite arm. You would think that only animals that have two forelimbs – a left and a right one – would show handedness, but that is actually not true. A study of the eight-armed octopus (Byrne at al., 2006) showed that the octopuses displayed a clear preference for one specific arm to reach into an experimental maze to retrieve a food reward. This shows that limb preferences are not limited to organisms with two forelimbs like cats and dogs.
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Masunari N, Sekiné K, Kang BJ, Takada Y, Hatakeyama M, Saigusa M. (2020). Ontogeny of Cheliped Laterality and Mechanisms of Reversal of Handedness in the Durophagous Gazami Crab, Portunus trituberculatus. Biol Bull, 238, 25‐40.
Ocklenburg S, Isparta S, Peterburs J, Papadatou-Pastou M. (2019). Paw preferences in cats and dogs: Meta-analysis. Laterality, 24, 647‐677.
Papadatou-Pastou M, Ntolka E, Schmitz J, Martin M, Munafò MR, Ocklenburg S, Paracchini S. (2020). Human handedness: A meta-analysis. Psychol Bull, 146, 481-524
Sieg AE, Zandonà E, Izzo VM, Paladino FV, Spotila JR. (2010). Population level "flipperedness" in the eastern Pacific leatherback turtle. Behav Brain Res, 206, 135‐138.
Ströckens F, Güntürkün O, Ocklenburg S. (2013). Limb preferences in non-human vertebrates. Laterality, 18, 536-575.