A genetic predisposition to happiness can be clearly observed in infants. For example,some babies are born with a naturally higher amount of activity in the left side of the prefrontal cortex. in one experiment, scientists predicted that these babies would exhibit less anxiety than others upon being separated from their mothers. Results confirmed the prediction. the experimenters concluded that, as many parents will attest,some babies are born with a happy temperament while others are not. Environmental influences up until the end of adolescence,when the brain is highly plastic or changeable,can also have profound effect. while a loving and nurturing parent may be able to raise a child's happiness set point,an angry and critical one can lower it considerably. this happiness set point refers to an emotional baseline to which a person returns after a dramatically positive or negative or negative life event such as winning the lottery or losing a partner. some studies have shown that life circumstances such as these do not premanently alter a preson's fundamental temperament. instead, individuals tend to return to their happiness baseline after the novelty of the event has worn off.