Contrary to popular perception, today’s teenagers are actually growing up more slowly than their predecessors, with 18-year-olds now behaving like 15-year-olds of yesteryears, suggests new research.

The findings published in the journal Child Development suggest that today’s teenagers are taking longer to engage in adult activities such as drinking alcohol, working, driving, or having sex.

“The developmental trajectory of adolescence has slowed, with teenagers growing up more slowly than they used to,” explained Jean Twenge, Professor of Psychology at San Diego State University in the US and lead author of the study.

“In terms of adult activities, 18-year-olds now look like 15-year-olds once did,” Twenge said.

The researchers examined how often teenagers engaged in activities that adults do and that children do not, including dating, working for pay, going out without parents, driving and having sex.

They analysed seven large surveys of 8.3 million 13- to 19-year-olds between 1976 and 2016.

The surveys were nationally representative, reflecting the population of US teenagers in terms of gender, race/ethnicity, socioeconomic status and geographic region.

In the surveys, teenagers were asked how they used their time, including their engagement in one or more adult activities, allowing researchers to compare teens in the 2010s to teenagers in the 2000s, 1990s, 1980s and 1970s.

The study found that today’s adolescents are less likely than their predecessors to take part in activities typically undertaken by adults.

The researchers also examined how changes in family size, life expectancy, education and the economy may have influenced the speed at which teenagers take on adult activities.

The trend toward engaging in fewer adult activities cannot be explained by time spent on homework or extracurricular activities because time doing those activities decreased among eighth and tenth graders and was steady among twelfth graders and college students, the researchers said.

The decline may be linked to the time teenagers spend online, which increased markedly, the authors noted.

“Our study suggests that teenagers today are taking longer to embrace both adult responsibilities (such as driving and working) and adult pleasures (such as sex and alcohol),” study co-author Heejung Park, Assistant Professor of Psychology at Bryn Mawr College in Pennsylvania, said.