To test your pet dog, you can place a treat-filled Kong toy directly in front of your dog and see which paw he or she uses to hold it to get the food out. A dog may use either paw or both paws.
To test your pet cat, you can set a “food puzzle” by putting a treat inside a glass jar and watching to see which paw your cat uses. Don’t forget to repeat it lots of times and take notes to see whether the effect is real or just random chance!
Horses also seem to prefer to circle in one direction rather than the other. Meanwhile, one study suggests that kangaroos are almost exclusively lefties, although the neural basis for this is unknown.
Lateralisation and brain function
In humans, the left hemisphere is mainly associated with analytical processes and language and the right hemisphere with orientation, awareness and musical abilities, although this dichotomy is simplistic at best.
Is there evidence of lateralised brain function in non-human animals too? A team of Italian researchers think so. They found that dogs wag their tails to the right when they see something they want to approach, and to the left when confronted with something they would rather avoid. This suggests that, just as for people, the right and left halves of the brain do different jobs in controlling emotions.
Laterality is also connected to the direction in which hair grows (so-called stuctural laterality), or even to the senses (sensory laterality). Many animals use they left eye and left ear (indicating right brain activation) more often than the right ones when investigating objects that are potentially frightening. However, asymmetries in olfactory processing (nostril use) are less well understood.
The left or right bias in sensory laterality is separate from that of motor laterality (or handedness). However, some researchers think that side preference is linked to the direction of hair whorls (“cow licks”), which can grow in a clockwise or anticlockwise direction. More right-handed people have a clockwise hair pattern, although it is unclear if this is true of other animals.
The direction of hair growth and handedness are also related to temperament. Left-handed people might be more vulnerable to stress, as are left-pawed dogs and many other animals. In general, many animals, including humans, that have a clockwise hair whorl are less stress-prone than those with anticlockwise hair growth. The position of the hair whorl also matters; cattle and horses with hair whorls directly above the eyes are more typically difficult to handle than those with whorls lower down on the face.
Elsewhere in the animal kingdom, snails also have a form of laterality, despite having a very different nervous system to vertebrates like us. Their shells spiral in either a “right-handed” or “left-handed” direction – a form of physical asymmetry called “chirality”. This chirality is inherited – snails can only mate with matching snails.