When I was a senior in high school in 1999, I read a book titled A Complete idiot's guide to increasing your IQ. Of course, you can tell just from the title of the book that the author was claiming that one can increase one's IQ. But, more specifically, the author was claiming that an adult can increase an adult's IQ. The author claimed that when an adult thinks, more synaptic connections were made between the person's neurons. These synaptic connections apparently remain after the person stops thinking about whatever complex material the person was thinking about. The author claimed that synaptic connections are what makes a person intelligent. The author implied not just that an adult can score better on IQ tests, but that g ( Charles Spearman's general mental factor) can actually be increased in adults. I have also read Charles Murray's and Dick Hernstein's book The Bell Curve. Murray and Hernstein's position is that IQ becomes fixed and stable by the time a person is 18. Murray and Hernstein don't think that IQ can be improved. What do psychologists think about this? What is the consensus among psychologists as to the answer to the question : can IQ be increased in adults? When a person thinks about something complex, do new synaptic connections form? Do the new connections remain after the person stops thinking about the complex issue?