Did you know your dog could be left-or right-handed...hem pawed, just like you?
Some vertebrate species tend to perform some behaviours in an asymmetrical way, as a reflection of a lateralised brain. Once it was thought that a lateralised briain was prerogative of humans, now we know that many other species including chimps, dogs, cats, horses, sheep, fish, birds...also have the two brain hemispheres specialised in processing different type on environmental information. We can say that, in general, the left hemisphere would be involved in the control of approach/proactive behaviours, it’s activated during routine-learned templates, focused attention and during prey capture. In contrast, the right hemisphere has complementary specializations such as withdrawal/reactive behaviours, it’s activated during novel situations and it’s involved in escape/emergency and stress responses.
Limb preference (i.e. the preferred use of one hand/paw to perform a task) is associated with greater activity of the contralateral motor cortex, thus, the observation of a bias in hand (or paw) use can be considered an indicator of brain laterality. It should be easy now to understand how hand/paw preference, brain activity and the expression of emotions, reactivity and personality are all related to each other. This is why in the past two decades researchers started to observe lateral behaviour in animals and investigate possible links with specific behavioural traits.
Photo credits Adam DS Milligan
In one of my most recent papers published on the Journal of Comparative Psychology, for example, we studied the association between lateral bias and personality traits in dogs. More specifically, we investigated whether lateralized (left or right) and ambilateral dogs differed in their behavioral response to a standardized personality test. Motor laterality can be scored in different ways, and for this study we used two different tasks. In the first task, we observed which paw the dog used to pin down a filled toy to retrieve the food; in the second task, we observed which paw the dog would mainly use to step off a step.
Results showed that ambilateral dogs (i.e. using both paws the same amount of times) were either more reactive (e.g. aggressive) during the personality test, or more excitable (e.g. exuberant greeting, more playful). Thus, overall, we found evidence of a link between canine personality and behavioral laterality, and this was especially true for those traits relating to stronger emotional reactivity.
The use of laterality as a proxy measure for behavioural differences in dogs has important applied outcomes such as helping predicting suitable working dogs or coping abilities in a shelter environment etc. At the moment, I'm following up on this study and assessing the lateral bias in dogs that have severe history of aggressive behaviour, fear or anxiety to see if there is a clear pattern of relation between these traits and hemispheric lateralisation.