What are dreams for? A handful of theories predominate. Sigmund Freud famously contended that they reveal hidden truths and wishes.  More recent research suggests that they may help us process intense emotions,  or perhaps sort through and consolidate memories,  or make sense of random neuron activity,  or rehearse responses to threatening situations.  Others argue that dreams have no evolutionary function, but simply dramatize personal concerns. 
Despite being largely unsupported by evidence, Freud’s view maintains a strong following around the world. Researchers found that students in the U.S., South Korea, and India were much more likely to say that dreams reveal hidden truths than to endorse better-substantiated theories.  Relatedly, people put great stock in their dreams: In the same study, respondents said that dreaming about a plane crash would cause them more anxiety than an official warning about a terrorist attack.
Even if dreams can’t foretell the future, they seem to expose our shared fascinations. The majority of dreams occur during REM sleep cycles, of which the average person has four or five a night. Eight percent of dreams are about sex, a rate that holds for both women and men—though women are twice as likely as men to have sexual dreams about a public figure, while men are twice as likely to dream about multiple partners.  Anxiety is also rife: A study of Canadian university students found the most common dream topics, apart from sex, to be school, falling, being chased, and arriving too late for something.