NewsBlow your nose with your left hand

Blow your nose with your left hand

On World Left-Handed Day this Friday, a look into the animal world – where left-handers are quite common.

Around every tenth person in the world is left-handed. This is the result of the largest meta-study to date on the topic from 2020, which was carried out by an international team of scientists and which also includes the German biopsychologist Sebastian Ocklenburg from the Ruhr University in Bochum.

The question arises: Are there actually any animals that prefer a certain paw or limb, i.e. are also left-handed, if you may say so? Researchers at the Ruhr University have also addressed this question. In a meta-study, they are evaluating scientific studies on 119 animal species – from amphibians, fish and reptiles to birds and monkeys. They found that just under 32 percent of these animal species did not prefer either side. Everyone else did so very well. And there are even quite a number of animals that give preference to their left paw or limb.

Ocklenburg has also investigated this in more detail with teams of scientists in further studies. It was found that cats, for example, use their left paws much more often than we humans use our left hand. 36 percent of 844 tested animals prefer their left paw, 39 percent the right. But not all of the cats examined in 16 different studies have committed themselves to one paw: every fourth domestic cat sometimes took its left and sometimes its right paw to help.

The situation is similar for dogs, with one interesting exception: the proportion of dogs that were “ambilateral”, as the researchers put it, that is, not tied to one side, was significantly higher at 37 percent. Out of 1132 dogs tested in 19 studies, 347 (32 percent) preferred the left paw, while 418 animals (37 percent) were right-hand paws, so to speak. “In the cats, but not in the dogs, we found significant gender-specific differences, with the female animals more often having a right laterality than the male animals,” says Ocklenburg.

With more power on the right?

In contrast, no such sex-specific differences were found in mice and rats. “There was no percentage difference between the animals’ preference for the left or right paw.” Left-handedness is apparently even more common among kangaroos than in dogs and cats or rats and mice, as a Russian-Australian study found. Researchers led by the zoologist Andrey Giljov from the State University of Saint Petersburg and Janeane Ingram from the University of Tasmania observed various species of kangaroos and other marsupials in the wild in Australia. They found that wild kangaroos (eastern gray kangaroos and red giant kangaroos) naturally use their left hand for all everyday things: cleaning and caring for their noses, picking leaves, bending branches.

In contrast, red-necked wallabies preferred their left hand for more sensitive tasks and their right hand more for challenges that required more strength. However, it cannot be concluded from this that animals generally perform more demanding tasks with their left hand and that the right paw is used when strength is required. At least that is what a study by Italian scientists suggests. Professor Paolo Zucca from the University of Teramo and his team found in a study with bats (Miniopterus Schreibersii) that the animals preferred their left forelimbs when they were asked to climb a plastic cylinder in the laboratory.

The preference for left or right does not end with the hands or paws. As with us humans, there are animals that give priority to their right or left eye or rather listen to their left or right ear. This left orientation can be particularly pronounced in Roman snails. The snail’s shell is usually right-wound. But there are also animals that have a left-handed snail shell. However, these are so rare that they are even referred to as the snail king. Angus Davison and Philippe Thomas from the University of Nottingham, who have done extensive research on snails, estimate that the chance of finding a snail king among Roman snails is around one in forty thousand. Other researchers assume one in a million. Incidentally, in these special animals not only the casing is reversed, but also all organs – which causes real problems for the snails when mating and thus explains their rarity.

There is something similar in humans: situs inversus is the name of the anatomical peculiarity in which some organs are mirror-inverted in the body.

(By Christian Satorius)

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