Interest in the opposite sex usually begins at puberty and gradually evolves into casual interactions, followed by group-based dating by the midteens, previous research has shown.
Exclusive partnerships are formed mostly later in adolescence.
Separate questionnaires assessed personality traits, such as shyness, depression, and aggressive or delinquent behaviors.
The early-starting group began dating at the age of 11.6 years, on average, compared with 12.9 years for on-time teens and 14.9 years for late bloomers.
These experiences can increase the risk of unsafe sexual activity, alcohol use and delinquent behaviors, the study says.
Late-starting daters, while also out of step with peers, appeared to have no apparent social or emotional difficulties.
The study, by researchers at York University in Toronto, used data collected from 1996 to 2003 on 698 students from 12 local schools.