Evolution, stress, and sensitive periods: The influence of unpredictability in early versus late childhood on sex and risky behavior.

Researchers tested how harshness and unpredictability experienced in early childhood (age 0-5) and in later childhood (age 6-16) predicted sexual and risky behavior at age 23. Findings showed the strongest predictor of both sexual and risky behavior was an unpredictable environment between ages 0 and 5. Individuals exposed to more unpredictable, rapidly changing environments during the first 5 years of life had more sexual partners, engaged in more aggressive and delinquent behaviors, and were more likely to be associated with criminal activities by age 23. For the most part, exposure to either harsh environments or experiencing unpredictability in later childhood (age 6-16) was not significantly related to the same outcomes.