Infants who sweat less in response to scary situations at age one show more physical and verbal aggression at age three, according to new research by Cardiff University.
Lower levels of sweat, as measured by skin conductance activity (SCA), have been linked with conduct disorder and aggressive behaviour in children and adolescents.
Leader of the study, Professor Stefanie van Goozen of Cardiff University’s School of Psychology hypothesizes that "aggressive children may have lower levels of physiological arousal because they don’t experience the same level of emotional arousal in response to fearful situations as their less aggressive peers. Because they have a weaker fear response, they are more likely to engage in antisocial behaviour."
Researchers in the School of Psychology wanted to know whether the link between low SCA and aggressive behaviours could be observed even as early as infancy. To investigate this, researchers attached recording electrodes to infants’ feet at age one and measured their skin conductance at rest, in response to loud noises, and after encountering a fear-inducing remote-controlled robot. Data was also collected on their aggressive behaviours at age three, as rated by the infants’ mothers.
The results revealed that one-year-old infants with lower SCA at rest and during the robot encounter were more physically and verbally aggressive at age three.
It was also gleaned that SCA was the only factor in the study that predicted later aggression. The other measures taken at infancy - mothers’ reports of their infants’ temperament, for instance - did not predict aggression two years later.
These findings suggest that while a physiological measure (SCA) taken in infancy predicts aggression, mothers’ observations do not.
"This runs counter to what many developmental psychologists would expect, namely that a mother is the best source of information about her child," van Goozen notes.
At the same time, this research has important implications for intervention strategies:
"These findings show that it is possible to identify at-risk children long before problematic behaviour is readily observable," van Goozen concludes. "Identifying precursors of disorder in the context of typical development can inform the implementation of effective prevention programs and ultimately reduce the psychological and economic costs of antisocial behaviour to society."
Professor Adrian Raine, Chair of the Department of Criminology at the University of Pennsylvania said:
"Stefanie van Goozen’s latest novel findings are powerful in showing that objective physiological measures predict to later aggression over and above other measures. If these new results can be replicated and extended to other ages, they have potentially important implications for the future prediction of aggressive and violent behaviour. They highlight the promise of biological measures too in better understanding the etiology of fearless aggressive behaviour"
Co-authors of this research include Dr Erika Baker, Dr Katherine Shelton, Dr Eugenia Baibazarova, and Professor Dale Hay of Cardiff University.
The findings will be published this week in Psychological Science, a journal of the Association for Psychological Science.
School of Psychology