Lateralized Function in Pets: Lefties and Righties in Cats and Dogs
Stefanie Schwartz, DVM, MSc, Dip. ACVB
Are you a “righty”? Do “lefties” run in your family? Accumulating evidence suggests that some animals have a preferred side, too. A growing body of evidence suggests that male cats and dogs (and other species, too) tend to be “left-pawed” and females are more likely to be “right-pawed”. Studies of neutered pets show no preference for using one paw over the other. Breed does not seem to predispose to pawedness in a study of Boxers, Pugs, Whippets and Greyhounds.
Another study in domestic cats found that cats sometimes appeared to be ambidextrous and used either paw. However, the more motivated the cat was to reach a treat, the more it tended to use a preferred paw. Lateralized function in cats depends upon the task and reward offered. What wouldn’t Garfield do for lasagna?
Handedness in Humans
Compared to other species studied so far, only humans are more likely to be right-handed; about 10 – 13 % of people around the world are left-handed. The brain has two cerebral hemispheres and each hemisphere controls the contralateral side of the body. The left side dominates individuals who are right-handed; the right side dominates those who are left-handed. The left hemisphere is the center for language, logic, mathematics and science; it processes data sequentially. The right side of the brain synthesizes data and is the source of imagination, dreams, art, and music. This does not mean that lefties are more talented artists, although many are.
Most “lefties” have a genetic basis; left-handedness definitely runs in families and at least one gene responsible for left-handedness has been isolated. There is likely more than one gene responsible because children born to two left-handed parents only have a 30% to 40% chance of being left-handed. If both parents are left-handed and this tendency is a recessive trait, then all of their children should be left-handed. Handedness is likely determined by many genetic, learned and environmental factors. For instance, premature birth and dystocia may injure the left hemisphere and result in a shift of language and dominant limb function to the right hemisphere.
Sex Hormones and Functional Lateralization
About 90% of all humans are right-handed; most southpaws are males. It has been suggested, but not substantiated, that testosterone might slow left hemisphere development in the male fetus and might account for left-handedness in humans. Right brain (left handedness) may have specialization in responding to novelty; this might have adaptive significance particularly in males of many species.
A heightened awareness of situational factors may have granted survival advantage in human males during hunting expeditions or conflict between males and clans. Research in Australia concluded that dogs without any distinct paw preference could not be trained to the same level as those with a specific paw preference. This might also support the more consistent performance of intact male dogs for police and other paramilitary K-9 units (left-pawed).
Paw Preference, Dis-Ease and Disease
An American study determined that ambidextrous pets (no bias for either paw when chewing on a bone or special chew toy) were at higher risk for behavior problems, separation anxiety and noise phobia. Ambidextrous dogs showed extreme reactivity to thunderstorm and fireworks compared to both left and right-pawed dogs.
Future clarification may help to breed dogs that are more emotionally stable. For example, working dogs selected for contraband and bomb detection are often rejected from explosive and sniffer dog detection programs because of noise phobia, sometimes after years of training and expense.
Finally, statistical studies in human populations have also suggested possible correlations between left-handedness and diseases such as allergies, epilepsy, and eczema. While it is too soon to know for certain, such predispositions could be confirmed someday in people and even among companion animals.
Test A Pet’s Paw Preference
Long-term species-specific studies of lateralization in nonhumans are required to determine if pawedness shifts over time or varies with context, experience and genetic predisposition. Until we know more, here are some fun tests (some are mine and others were used in the studies described earlier) to determine paw preference. During actual clinical trials, tests are performed about 100 times; a sample of 10 to 20 repetitions should be enough for the curious yet busy pet parent or veterinarian.
· Teach a dog to “shake”, record which paw is offered more often;
· Place a treat or a toy under the sofa just out of a dog’s reach and see which paw he uses to try to reach for it;
· Note which paw a cat uses to ‘trap’ a laser pointer light or swat at a dangling toy above the head;
· Put a small piece of tape on a pet’s muzzle and see which paw she uses to remove the tape.
Dr. Stefanie Schwartz is a board certified veterinary behaviorist who treats misbehaving patients in Southern California. For more details, please visit www.petbehavior.org or call (949) 342-6644.
© Stefanie Schwartz, 2014