Brain Asymmetry Changes a Dog's Wag and a Human's Mind

Handedness and tail wagging reveal clues about the mind of humans and canines.

Posted Nov 02, 2013

What is the connection between brain asymmetry and mental states in humans and in dogs? There are certain cognitive processes that are linked predominantly to the left or right side of the brain. Both the human and canine brain develop asymmetrically. 

A convenient measure of brain asymmetry in humans is hand dominance—in dogs it’s the wagging of a tail. Previous research has found that patients with schizophrenia are more likely to be left-handed than the general population; dogs tend to wag their tails to the left when they feel negative or threatened.

Two very different studies about brain asymmetry were released on October 31, 2013. In one study, researchers from Italy discovered that when dogs wag their tails to the right (left hemisphere activation) they are in a positive/approach mode and perceived as ‘friendly’ by other dogs. On the flip side, when a dog wags its tail to the left (right hemisphere activation) they are feeling negative/avoidance emotions and perceived as unfriendly or unfamiliar by other dogs. In a completely different study, researchers at Yale found that people with psychotic disorders like schizophrenia are much more likely to be left-handed (right brain dominant).

There is one important caveat: I realize that it is bad science and reckless to make overly generalized statements about brain lateralization and differences between the left and right hemispheres. Much of what scientists understand about exactly how the mind and brain are connected is still an educated guess. These findings offer interesting food for thought and clues for ways we can put recent scientific findings into everyday practice to improve our lives. This is the objective of The Athlete's Way.

My father, Richard Bergland, was a neurosurgeon and neuroscientist who was one of the pioneers of bringing the idea of the right brain being the seat of creativity to a mainstream audience in the 1970s. My dad published a book called "Fabric of Mind" (Viking) and was one of the experts quoted in the bestselling book, “Drawing on the Right Side of the Brain.”

Later in his life my dad advocated that the entire brain works in concert, and that connectivity and symmetry between all hemispheres of the brain is the key to mental balance and peak performance. The debate over differences between left brain-right brain continues to rage on.

In many ways, it seems the more neuroscientists discover about brain asymmetry, the more mysterious the picture becomes. Handedness is a very rudimentary but complex reflection of being either left or right brain dominant. That said, clearly something is going on with handedness and personality.

Five of the past seven U.S. presidents were left-handed. Is this a coincidence? Being left handed is being linked to making someone both more prone to be a creative genius, trailblazer, leader etc. but also increasing the odds of being schizophrenic. If you’d like to read more on this topic please check out my Psychology Today blog, “Are Lefties More Likely to Be Champions and Leaders?”

Left Brain Tail Wagging Linked to Dog's Happiness

Dogs recognize and respond positively when another dog wags to the right, and negatively when another dog wags to the left. The findings of a new study titled “Seeing Left or Right Asymmetric Tail Wagging Produces Different Emotional Responses in Dogs” was published in the Cell Press journal Current Biology on October 31, 2013.

Like humans, dogs have asymmetrical brains, with the left and right hemispheres of both the cerebrum and cerebellum playing different roles in movement and emotion. In the Italian experiment, stimuli that could be expected to elicit approach tendencies, such as seeing a dog's owner, were associated with higher amplitude of tail wagging movements to the right side (left brain activation) and stimuli that could be expected to elicit withdrawal tendencies, such as seeing a dominant unfamiliar dog, were associated with higher amplitude of tail wagging movements to the left side (right brain activation).

The recent discovery builds on earlier research by the same Italian team, which found that dogs wag to the right when they feel positive emotions (i.e. upon seeing their owners) and to the left when they feel negative emotions (i.e. upon seeing an unfriendly dog). Biased tail-wagging to the left or right reflects what is happening in the dogs' brains. 

While monitoring the canines' reactions, the researchers showed dogs videos of other dogs with either left- or right-asymmetric tail wagging. When dogs saw another dog wagging to the left, their heart rates picked up and they began to look anxious. When dogs saw another dog wagging to the right, they stayed perfectly relaxed.

"The direction of tail wagging does in fact matter, and it matters in a way that matches hemispheric activation," says Giorgio Vallortigara of the Center for Mind/Brain Sciences of the University of Trento. "In other words, a dog looking to a dog wagging with a bias to the right side – and thus showing left-hemisphere activation as if it was experiencing some sort of positive/approach response – would also produce relaxed responses."

Vallortigara adds, "On the flip side, a dog looking to a dog wagging with a bias to the left – and thus showing right-hemisphere activation as if it was experiencing some sort of negative/withdrawal response – would also produce anxious and targeting responses as well as increased cardiac frequency. That is amazing, I think."

Vallortigara doesn't think that the dogs are necessarily intending to communicate these emotions to other dogs. Rather, he says, “the bias in tail wagging is likely the automatic byproduct of differential activation of the left versus the right side of the brain."

But that's not to say that the bias in wagging and its response might not find practical uses. Veterinarians and dog owners might do well to take note of this research. It could be that left/right directions of approach could be effectively used by vets during visits of the animals or that dummies could be used to exploit asymmetries of emotional responses, Vallortigara concludes.

Left-Handedness Linked to Schizophrenia

Being left-handed has been linked to many mental disorders, but Yale researcher Jadon Webb and his colleagues have found that among those with mental illnesses, people with psychotic disorders like schizophrenia are much more likely to be left-handed than those with mood disorders like depression or bipolar syndrome.

The new study titled,“Left-Handedness Among a Community Sample of Psychiatric Outpatients Suffering From Mood and Psychotic Disorders," is published in the October-December 2013 issue of the journal SAGE Open.

About 10% of the U.S. population is left-handed while 40% of those with schizophrenia are lefties. When comparing all patients with mental disorders, the research team at Yale found that 11% of those diagnosed with mood disorders such as depression and bipolar disorder are lefties, which mirrors the rate in the general population. But according to Webb, a child and adolescent psychiatry fellow at the Yale Child Study Center with an interest in biomarkers of psychosis, "a striking of 40% of those with schizophrenia or schizoaffective disorder are left-handed."

"In general, people with psychosis are those who have lost touch with reality in some way, through hallucinations, delusions, or false beliefs, and it is notable that this symptom constellation seems to correlate with being left-handed," said Webb. "Finding biomarkers such as this can hopefully enable us to identify and differentiate mental disorders earlier, and perhaps one day tailor treatment in more effective ways."

What sets this study apart from other handedness research is the simplicity of the questionnaire and analysis, said Webb. Patients who were attending their usual check-ups at the mental health facility were simply asked "What hand do you write with?"

"This told us much of what we needed to know in a very simple, practical way," said Webb. "Doing a simple analysis meant that there were no obstacles to participating and we had a very high participation rate of 97%. Patients dealing with serious symptoms of psychosis might have had a harder time participating in a more complicated set of questions or tests. By keeping the survey simple, we were able to get an accurate snapshot of a hard-to-study subgroup of mentally ill people – those who are often poverty-stricken with very poor family and community support."

Conclusion: Brain Symmetry Is Key to Mental and Physical Balance

More and more research is confirming that connectivity and symmetry between all hemispheres of the brain is key to physical and mental well-being and to maximizing your personal potential. Daily habits of mindset and behavior that reinforce brain asymmetry could lock a person into an unbalanced state-of-mind and prevent someone from tapping the full spectrum of his or her creative, intellectual and emotional capacities.

How do you create brain symmetry? In humans and dogs alike, I believe that rhythmic aerobic exercise (like walking or jogging) is one way to automatically engage all four hemispheres of your brain and strengthen symmetry and connectivity of all brain hemispheres through neurogenesis and neuroplasticity.

The very nature of aerobic exercise automatically creates fluid connectivity that strengthens the neural connections between all brain hemispheres. The coordination and balance needed to walk, jog, swim or bike requires the rhythmic coordination of brain hemispheres and strengthens the connection between all four brain hemispheres.

Aerobic exercise requires communication across the corpus callosum and vermis (left-right lateralization) of the cerebrum and cerebellum respectively, and across the midbrain (up-down lateralization) between the cerebrum and cerebellum. Keeping the line of communication open and engaged between all four brain hemispheres reinforces brain symmetry.

Aerobic exercise is not a panacea, but in addition to other daily lifestyle choices and cognitive therapies it can help to improve brain symmetry. The pros and cons of being left-handed or the emotional states linked to wagging bias confirms that being left brain or right brain dominant effects humans and canines. The neuroscience of how this works is still a mystery and requires more research.

If you’d like to read more on this topic please check out my Psychology Today blogs: “Video Gaming Can Increase Brain Size and Connectivity”, ”Better Motor Skills Linked to Higher Academic Scores”, “Einstein’s Genius Linked to Well-Connected Brain Hemispheres”, ”The ‘Right Brain’ Is Not the Only Source of Creativity", "Toward a New Split-Brain Model: Up Brain-Down Brain" and "Squeeze a Ball With Your Left Hand to Increase Creativity."