A rigorous study conducted by the Swedish army showed that young men who were heavy cannabis users by age 18 were __________ times more likely to develop schizophrenia than those who weren't.

Research on biological influences on gender typing reveals that

A) sex differences in play and personality traits only appear in Western cultures. B) aggression and preference for same-sex playmates are widespread among mammalian species. C) preschool girls prefer to play in larger-group play with other girls. D) prenatally administered androgens decrease active play.

During puberty, boys

A. increase muscle strength by about 20 percent. B. increase muscle strength most noticeably in the legs. C. more than double their arm strength. D. decrease body fat by about 20 percent.