If your pre-teen kid is exhibiting antisocial behaviour, breaking the rules you lay down, or having problem paying attention, then the root cause could be the tendency he or she has for activities in the evening rather than in the morning.
The finding is based on a study conducted by researchers led by Elizabeth J. Susman at Penn State who are trying to understand how a characteristic titled 'morningness/eveningness', along with the ratio of cortisol readings taken in the morning and afternoon, influences young adolescent behaviour.
In humans, cortisol is responsible for regulating various behavioural traits such as the fight-flight response and immune activity that are connected to sensory acuity and aspects of learning and memory.
Cortisol normally spikes in the morning and falls to a plateau by afternoon and evening. Readings taken in the morning and afternoon usually show a significant drop, and scientists associate small differences in the readings with clinical depression and antisocial behaviour.
As a part of the study the researchers analysed the preference for morning or evening activities among a group of 111 boys and girls aged 8 to 13.
They then collected cortisol readings from saliva, and assessed the kids for a host of undesirable behavioural traits.
Results from the study suggest that a preference for eveningness is associated with traits of antisocial behaviour such as rule breaking, attention problems, and conduct disorder. However, these antisocial traits were seen only in boys.
"In girls, eveningness is associated just with relational aggression. This is behaviour specifically meant to hurt another child's friendship, or feelings of isolation," said Susman.
When the researchers factor in early puberty, the study finds that though it does not affect either the preference for mornings or evenings, or the cortisol ratio, earlier puberty is related to more antisocial behaviour in boys, and relational aggression in girls.
"The link between eveningness preference and antisocial behavior was previously associated only with older adolescents. The novel finding of the study is that the link is now apparent as early as 8 year old kids."
Susman thinks eveningness could make young adolescents vulnerable to antisocial behaviour.
"Eveningness contributes to lack of sleep, and this in turn causes problems such as lack of control and attention regulation, which are associated with antisocial behaviour and substance use," she added.
Parents need to be vigilant in recognizing early signs of eveningness, and not only encourage their kids to sleep early but also ensure they get the required amount of sleep, Susman noted.
The findings appear in the July 2007 issue of Developmental Psychology.