Dr. Sergio Pellis

Contact Information
Phone Number: 
(403) 329-2078

Sergio M. Pellis has been a Professor at the University of Lethbridge since 1990 with the main focus of his research being on the role peer-peer play has in the development of social competence. Using various species, ranging from laboratory rodents to primates, such as the great apes, Pellis has shown that rough-and-tumble play is composed of dissociable subcomponents (e.g., attack, defense) and that there are species differences in how such play can be modified at different ages and contexts. With detailed studies on rats, Pellis has shown that this form of play is reorganized in the juvenile period, when play is most frequent, and that this reorganization is dependent upon cortical modulation of the subcortical circuits that produce play. Furthermore, Pellis has shown that the experiences derived from rough-and-tumble play during the juvenile period serve to modify the development of the neurons of the prefrontal cortex. It is these changes in the prefrontal cortex that likely mediates the effects of play on the development of social competency. Ongoing research in the Pellis laboratory will characterize the experiences that are instrumental in affecting these brain changes, the brain changes themselves and their functional involvement in executing effective social behaviour, and why some species have evolved this function for play whereas others have not.

What first piqued your interest in your research discipline?: 

It came in several steps. The first, when I was 5 years old, and realized that my ambition in life was to study animals, the second, midway through my undergraduate degree in Zoology, when I realized that the behaviour of animals was what turned me on the most, the third, by the end of my degree when I realized that the most intriguing aspect of animal behaviour was how it develops, and the fourth step was when I discovered that play, a feature of behaviour common to the childhood of many animals, posed an intriguing problem concerning development. The last step came when I was doing post-doctoral research in Behavioural Neuroscience and realized that looking at the brain was another important avenue by which to understand behaviour and how it changes over time. Altogether, this led to an interest in how the brain produces and regulates play behaviour and how play behaviour changes the functioning of the brain. Many laboratories have shown how the absence of social play experience in juvenile rats leads to adults that are socially deficient. The core discoveries in my laboratory have been that socially reared rats with damage to prefrontal cortex mimic the social deficiencies of rats with intact brains but deprived of play as juveniles, and that the absence of play experience leads to anatomically measurable changes in the neurons of the prefrontal cortex. Taken together, these findings show that play derived experiences in the juvenile period influence the development of social skills and that these skills are dependent on the functional modification of the prefrontal cortex.

How is your research applicable in “the real world”?: 

Aside from providing a model for further research into understanding the mechanisms that underlie the feedback relationship between brain and behaviour, the “real world” applicability of my research concerns our societal practices in child rearing. The current trend for both parents and schools to curtail the opportunity for free play in general, and rough and tumble play in particular, may have important implications for understanding how children can sharpen their social skills. Indeed, there are data, albeit given the limits imposed on research on humans, based on correlations, that show that children with greater opportunity to engage in free play, especially rough housing play, are socially more proficient and score better in their academic work. Our laboratory-based experiments on rats provide evidence for the causal mechanisms by which play may have these beneficial effects. By refining the functional organization of the prefrontal cortex, it enhances the executive function of this part of the brain, enabling improved emotional control and impulse control, which leads to improved attention and decision-making. Some of these beneficial effects may be indirect and some direct. Indirectly, improving children’s social skills may make their time in the social confines of school more pleasant and consequently place them in a better mood to participate in academic pursuits. Directly, improved executive functions make negotiating the complex demands of school more manageable and so children are in a better position to learn new material. Again, our rat model provides the means to test these possibilities experimentally and also to generate precise predictions that can be tested with children within the home and school.

What is the greatest honour you have received in your career?: 

To have been able to work on the problem that has been of most interest to me, to have made some novel discoveries and to have peers use some of my work as a basis for developing and testing hypotheses. Even more exciting has been independent support for some of the ideas generated in my laboratory. That is about as good as it gets.

How important are students to your research endeavours?: 

Undergraduate and graduate students as well as post-doctoral fellows have been an instrumental part of my research program and the successes that I have had in that program. Students bring several assets to one’s research program. First, they are young and full of energy. Second, they are motivated to succeed. Third, they bring fresh eyes and insights to the problem under investigation. The best students that I have had are those who have challenged what I told them is important or noticed something new in the phenomenon that I had missed. I have found that directing a good student to a problem, giving them ownership of that problem, and letting them loose on it, has, many times, produced major breakthroughs in the research. I wouldn’t have reached the level of understanding about play that I have without the valuable contributions by the students who have worked with me.

If you had unlimited funds, which areas of research would you invest?: 

As well as unlimited funds, this scenario would require multiple lifetimes, but if you are going to dream, dream big. I would still study play, but I would push the two lines of research that I study know to greater depth. First, I would combine levels of analysis – behaviour, brain anatomy at the cellular and sub-cellular level, genetic and other molecular changes associated with play, and electrophysiology of specific brain areas known to be associated with play. Such an integrated approach would allow a full mapping of the brain changing effects of play experience in the juvenile period, and characterize how those changes transform the functional capabilities of the brain. To succeed in such a broad endeavour not only would need more laboratory space and equipment, but the ability to recruit post-doctoral researchers versed in the methodologies beyond my knowledge. Without such an all out integrative endeavour, progress will be slower, with my laboratory providing the pieces of the puzzle that we are equipped to deal with and piecing together what we find with finds, in other domains, from other laboratories.


Second, one of the insights that has arisen from my work on the play of rats and other rodents is the finding that the ability to ‘play with play’ depends on specialized mechanisms in the cortex, particularly the prefrontal cortex. It is likely that changes in these mechanisms have led to the evolution of the human exaggeration of fantasy in their play. Over the past 20 years, I have collected videotapes on the rough and tumble play of about 54 species of primates. Play is ubiquitous across the order Primates, but its complexity varies, with some lineages showing play about as complex as seen in rats and for others showing play closer to the form seen in humans. Our data show that those lineages with brains more similar to humans have elements of fantasy incorporated into their rough and tumble play. A major question would be whether the more complex play of some lineages leads to having modified patterns of development. For example, unlike other laboratory rodents, rats have a modified pattern of play in the peak juvenile period and this modified pattern of play appears to be critical for the experiences that modify the prefrontal cortex. Similarly, variation in the degree of fantasy in play may involve variation in the pattern of development across the primate order. Based on the comparative data available, I would select about 12 species, ranging from the most primitive to the most derived (lorises to chimpanzees), and then carefully map the behavioural content of play from birth to sexual maturity. This would involve a large number of graduate students, with each studying one or two species in detail. Such an endeavour would finally answer the question of how humans have evolved their seemingly unique features of play, and so would be able to characterize the brain changes that are involved in producing those features.

In the news: 

"Rough play a key to brain development: researcher," Lethbridge Herald March 2009
"Meet Sergio Pellis..." Legend, September 2008 (see p. 4)
"Who's doing what" Lethbridge Herald June 10, 2008
"Serious fun" FIAT_Spring_2008
"Board appoints new Research Chairs" Legend, April 2007 (see p. 4)
"Roughhousing rats offer insights" Lethbridge Herald March 23, 2007

Current CV