Complex sentence: Based on studies of animal behavior suggesting that sexual patterns depend on learning, he argued that human sexual orientation also depends on learning, and that the reason most people are exclusively heterosexual is that their upbringing has made them expect and want to be heterosexual.
Split into simpler sentences: Based on studies of animal behavior suggesting that sexual patterns depend on learning, he argued that human sexual orientation also depends on learning. Tripp maintained that most people are heterosexual because their upbringing has made them expect and want to be heterosexual.