Babies born in winter are more likely to be adventure-seekers in adulthood, according to research presented at a British Psychological Society conference yesterday.

People with birthdays in October, November and December are much more inclined to take up risky sports, enjoy wild parties and shun monotony than those who were born in the summer. Experts believe that the differences may be due to varying levels of the brain chemical dopamine at birth.

Winter babies had higher levels of the chemical, which allows people to feel sensations of reward, pleasure and motivation. Dopamine is also linked to melatonin, a hormone that governs a person's response to daylight and ability to sleep.

Dr Carol Joinson, of the Open University, said: "Melatonin inhibits dopamine, so the affect seems to do with the amounts of daylight when babies are born. If they are born during the winter when there is less light, they have less melatonin and more dopamine so they are more sensation-seeking."

Behavioural traits included enjoying sports such as skiing or scuba diving, preferring wild parties to quiet gatherings, having multiple sexual partners and drinking, gambling and taking drugs.

Dr Joinson found babies born between October and March demonstrated higher levels of sensation-seeking behaviour by the time they were in their 20s and 30s than people born between April and September. And that type of behaviour continued until they were 45.