Americans love to read about psychology, but much of what they think are scientific facts aren’t supported by research, says Scott O. Lilienfeld, PhD, a psychology professor at Emory University in Atlanta. “There’s a lot of information out there, but there’s also a lot of misinformation.”

Consider the idea that people use just 10 percent of their brains. Though researchers have found that healthy people use pretty much all of the organ, a whopping 59 percent of college-educated people believe that oft-debunked “fact.”

To correct that and other tenacious misconceptions, Lilienfeld has written “50 Great Myths of Popular Psychology” (Wiley-Blackwell, 2010) with co-authors Steven Jay Lynn, PhD; John Ruscio, PhD; and the late Barry L. Beyerstein, PhD.

“It’s always possible that some current accepted truth could be overturned,” says Lilienfeld. “But we are trying to document the myths that have been pretty well debunked by lots of high-quality research.”

Here are a few of the myths they address:

  • Criminal profiling helps solve crimes. Experts who glean the personal characteristics of criminals from crime scenes have become fixtures of prime-time television, but a 2007 meta-analysis found that profilers’ predictions are barely better than those of laypeople (Criminal Justice and Behavior, Vol. 34, No. 4). Such experts typically draw on well-known data about criminals — they know, for example, that most serial killers are white males — and create profiles based on that information. The upshot? Any reasonably intelligent person with access to crime and demographic data can make inferences that are about as accurate as those made by the pros, says Lilienfeld. “A computer program could do that as well as, or better, than a human,” says Lilienfeld. “Why the FBI still employs profilers, I don’t know.”

  • Abstinence is the only realistic treatment goal for alcoholics. Programs such as Alcoholics Anonymous claim that former alcoholics must abstain from drinking for the rest of their lives to avoid a relapse. However, interventions that teach people with alcoholism to drink socially without spiraling out of control can also be effective, according to a 1999 meta-analysis in the Journal of Counseling and Clinical Psychology (Vol. 67, No. 4). “These programs aren’t for everyone,” says Lilienfeld. “People with a long history of alcohol abuse or physiological problems resulting from drinking probably should still have abstinence as their goal.”

  • You can’t change highly heritable traits. This is one that even trips up scientists, says Lilienfeld. The problem comes from the fact that heritability tells us how much genes contribute to a particular trait in a given population, while many people mistakenly believe that heritability estimates how much genes contribute to a trait in a particular person. In fact, it’s possible, in principle, to change heritability estimates by simply varying the population or the environment you’re measuring. Consider the example of IQ: If we lived in a perfectly equitable society in which everyone had equal access to education and other environmental opportunities, a twin study of intelligence would find that IQ is nearly 100 percent heritable. That’s because people’s environments would be unvarying, so only genetic differences could account for variations in intelligence. Similarly, if we lived in an inequitable society where people were closely related, the study would find IQ to be almost 0 percent heritable. “We could actually use heritability estimates as a measure of how effective a social policy is,” Lilienfeld and his colleagues say.

  • Stress causes ulcers. More than half of Americans believe that stress leads to ulcers, according to a 1997 Centers for Disease Control and Prevention survey. But, thanks to research by Nobel Prize-winning scientists Barry Marshall, MD, and Robin Warren, MD, we know that peptic ulcers are caused by the bacterium H. pylori. Once the bacteria create a stomach-lining sore, however, stress can sometimes make it worse, researchers have found.

  • Only deeply depressed people commit suicide. Actually, only 13 percent to 41 percent of people who commit suicide meet diagnostic criteria for major depression, according to a 2007 meta-analysis (Current Opinion in Psychiatry, Vol. 20, No. 1). Substance abuse disorders, schizophrenia, panic disorder, social phobia, gender identity disorder, and borderline personality disorder also account for many suicides, research has found. The bottom line, says Lilienfeld, is that psychologists should screen for suicidal thoughts among anyone who expresses pervasive hopelessness — regardless of his or her diagnosis.