The Psychology of Left-Handed People and Southpaw Dogs

Does it make any difference if a human is left or right-handed or if a dog prefers to use his left or right paw when manipulating objects?

I am continually struck by the similarity in the behavior patterns of dogs and people. For example, for something like 30 years or so of my life, I studied the differences between right-handed and left-handed people. While handedness might seem like a trivial behavioral difference in a human population, it actually turns out to be an important marker since left-handers tend to differ in their emotional responses, health status, and even lifespan. In addition, left-handers are more likely to appear in various clinical populations, including those with severe psychological problems such as schizophrenia, addictions, learning disabilities, and depression. However one does not have to look at the extremes of behavior to find differences based on hand use. Generally speaking, left-handers who are quite normal in their behaviors still tend to be more emotionally responsive and sometimes show more difficulties in coping with stressful situations (see Coren, 1993 for a review).

The reason why this might be has to do with the way in which the hands are wired into the brain. The right hand is controlled by the left hemisphere of the brain while the left hand is controlled by the right hemisphere of the brain. The argument which is often made is that an individual who has a dominant right-hand, therefore, has a left hemisphere which is more dominant. The reasoning goes that because of this, any behavioral biases and predispositions associated with left hemispheric activity are more likely to dominate the person's behavior. In contrast, the characteristics of the right hemisphere will dominate the behaviors of a left-handed individual. This makes a difference because there is data which suggests that the left hemisphere of the brain tends to be more strongly associated with proactive, calm, rational and sociable behaviors. It controls such things as approaching, exploring, and interacting. The right hemisphere seems to be much more emotional and it tends to be associated with the controlling of reactive behaviors, and behaviors that have a high emotional intensity including the expressions of fear and aggression.

However, the general belief has been that humans and dogs are quite different when it comes to the effects of handedness (or paw preference in the case of dogs). Part of the reason is that in humans, there is a strong population bias with 90 percent of all people being right-handed, while in dogs, there is no strong population bias and any given dog appears to be equally likely to be either right or left-pawed. Nonetheless, the majority of dogs do have a paw preference and some scientists have begun to ask the question does that right or left paw preference makes any difference in terms of our ability to predict that dog's behavior in the same way that handedness helps to predict the behavior of people.

Some data that helps to provide an answer comes from a new study out of the Animal Behavior Center of the School of Psychology at Queens University in Belfast, Northern Ireland. Shanis Barnard, Deborah Wells, and Peter Hepper tested a group of dogs rescued by a shelter in Ballymena, Northern Ireland. They reasoned that this was a good sample of dogs to look at since dogs newly housed in an animal shelter often show a lot of emotion as they try to cope with this new, unfamiliar, and more impersonal environment.

To test the paw preference of each dog they used a Kong, which is a rubber toy made up of a set of partial spheres of different sizes with a hole in the bottom. This is useful because you can stuff some food in the hole. Now in order to get to the food, the dog must immobilize the Kong which would otherwise roll around, making it impossible to get at the treat hidden inside. To do this the dog usually places a paw on the toy. The paw that the dog chooses to use is an indication of the dog's paw preference. To make sure that the measure of paw preference is reliable a number of observations are taken while the dog chews or licks at the treat concealed inside the toy.

A dog holds a Kong down with his right paw.

Source: Alan Levine-Public Domain

Measures of the stress that the dog was experiencing were taken by monitoring the concentration of the stress hormone, cortisol, in the dog's urine. In addition, video records of the dog's behavior were analyzed for a variety of stress-related activities and signs.

I was surprised to find that the dogs showed patterns of behavior which would be consistent with predictions that you might make based on the data on human handedness. In general, the dogs who chose to use their left paw seemed to be more stressed and emotional and seemed to be having more difficulty adjusting to these new and unfamiliar surroundings. The authors conclude that, "Overall, it appears that a left-motor bias may be linked to a more negative affective state, a more reactive coping style, and a more challenging adaptation to novel environments."

So, once again, I am struck by the fact that parallels can be drawn between the behaviors of dogs and people even in subtle predictors such as which hand or which paw an individual chooses to use.

Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission