Carl Hart is a neuroscientist and drug addiction expert at Columbia University. In a recent TEDMED talk, Hart spoke about drug addiction and the many misconceptions surrounding the topic — and how those misconceptions can mislead drug policy.

Hart went into neuroscience to cure the drug addiction he blamed for causing crime and poverty in his old Miami neighborhood. But when he began to work on the issue, he learned that his assumptions were wrong.

About 80 to 90 percent of the people who use illegal drugs don't turn out addicts, Hart explained. As an example, Hart pointed to the three previous presidents, all of whom used drugs when they were younger. "Their drug use did not result in an inevitable downward spiral leading to debauchery and addiction," Hart said. "And the experience of these men is the rule, not the exception."

the findings show the problems are much more complicated than some believe

As Hart explained, many of the current assumptions about drug addiction are based on old animal experiments from the 1960s and 1970s. In these tests, animals were put in a cage with a lever that they could pull for a shot of a drug. Researchers found the animals would pull the lever until they died from an overdose.

Hart said these animals were never presented with an alternative, though. In other experiments, animals were given another option: a mate or a sweet treat. At that point, the animals began choosing the non-drug alternative, and they didn't take the drug until they died.

Hart followed up on these experiments with human participants in 2000 and 2012. His lab recruited meth and crack cocaine addicts, and the addicts were given the option to choose between a small amount of money or their drug of choice. When the money option was $5, they chose the money about half the time. When the money option was $20, they chose the money about eight out of 10 times.

The results, of course, don't diminish the real problems of crime, poverty, and drug addiction in some of America's communities. But the findings show the problems are much more complicated than some, including a younger Hart, believe.