15 May 2000
Smarter Teens Delay Sexual Relationships
by George Atkinson
Researchers have found that smarter adolescents start having sexual relations later than teens of average intelligence.
As a group, intelligent adolescents also tend to postpone any kind of lesser sexual activity - from holding hands and kissing to heavy petting - a new University of North Carolina at Chapel Hill study shows.
Perhaps surprisingly, the least intelligent teens also appear to delay various amorous contacts, but researchers don't know why. Parents or other guardians may shield the latter - especially girls - from sexual liaisons longer than others.
"An adolescent who scored 100, which was average on the test we used to measure intelligence, was one-and-a-half to almost five times as likely to have had sexual relations compared to teens who scored 120 or 130, depending on which age and sex group was considered," said Dr. Carolyn Halpern, assistant professor of maternal and child health at the UNC-CH School of Public Health.
"The association between test scores - or intelligence - and refraining from sexual intercourse was the same for blacks and whites, but was stronger for girls than for boys and stronger for older teens."
A report on the research, titled "Smart Teens Don't Have Sex (or Kiss Much Either)," appears in a recent issue of the Journal of Adolescent Health. Besides Halpern, authors are Dr. Kara Joyner of McGill University, and Drs. J. Richard Udry, Kenan professor of maternal and child health and sociology, and Chirayath Suchindran, professor of biostatistics, both at UNC-CH.
Researchers analyzed information from two separate samples of adolescents - the National Longitudinal Study of Adolescent Health (Add Health) and the Biosocial Factors in Adolescent Development project, both supported by the National Institute of Child Health and Human Development and other agencies.
The former study included data on about 12,000 adolescents enrolled in the seventh to 12th grades nationwide. The latter, used because it contained more specific information on different levels of sexual contact, followed about 100 white boys and 200 white and black girls over three- and two-year periods, respectively, in a single North Carolina county.
Both samples involved detailed, confidential surveys of teen-agers and their experiences and attitudes. Investigators used a test called the Peabody Picture Vocabulary Test to measure intelligence.
In the smaller biosocial factor group, where more information about sex was available, she and colleagues found that for each one point increase in test score, the chance of necking went down 2.5 percent for boys and 1.6 percent for girls. The likelihood of intercourse decreased 2.7 percent for boys and 1.7 percent for girls.
Controlling for such factors as adolescents' self-described physical attractiveness, grooming, personality and whether the adolescent had a romantic relationship in the previous 18 months did not change the results significantly, Halpern said.
Two findings surprised the researchers, she said.
First, the relationship between intelligence and postponing sex existed even for behaviors that have no obvious negative consequences such as kissing or light petting. It is commonly assumed that the link between good grades, which has been investigated more often than intelligence measures, and sexual postponement is due to adolescents' desire to safeguard future goals like college.
"Our results suggest that this is not the whole story," Halpern said. "It is hard to believe that teens avoid kissing because they see it as the start of a slippery slope to sexual intercourse and possible pregnancy."
The second surprise was that teens at both the high and the low end of the intelligence distribution were more likely to delay first sex, she said.
"We thought the relationship would be linear - that teens on the high end would be least likely to have sex, and teens on the low end would be most likely," Halpern said. "We thought teens of lower intelligence might be more vulnerable to being taken advantage of or less likely to consider possible negative consequences of having sex."
Although they could not determine exactly why, their analyzes suggested that processes underlying the behavior were different for lower- and higher-intelligence teens, she said.
"If a societal goal is to develop effective programs to help kids make healthier decisions, then we need to understand what leads to their decisions," Halpern said.