Growing familiarity with marijuana has been accompanied by growing support for legalization because people discovered through personal experience that the government was lying to them about the drug's hazards. But it is easier to demonize less popular drugs such as crack cocaine and methamphetamine, which in the public mind are still linked, as marijuana once was, with addiction, madness, and violence. Any attempt to question the use of force in dealing with these drugs therefore must begin by separating reality from horror stories.

That is where Carl Hart comes in. Hart, a neuropsychopharmacologist at Columbia who grew up in one of Miami's rougher neighborhoods, has done bold, path-breaking research that challenges widely accepted beliefs about crack and meth. In his inspiring and fascinating new memoir High Price, he describes both how he overcame his early disadvantages to secure a tenured position at an Ivy League university and how he came to question everything he thought he knew about drugs as he learned to think critically about the issue.

Before he became a scientist, Hart believed that people who use crack generally get hooked on it and thereby lose control of their behavior. But when he looked at the data on patterns of drug use as an academic, he could plainly see that only a small minority of people who try crack become heavy users. "Even at the peak [of] widespread use," he writes, "only 10–20 percent of crack cocaine users became addicted." According to the National Survey on Drug Use and Health, just 3 percent of Americans who have tried this reputedly irresistible and inescapable drug have smoked it in the last month.

Contrary to what anti-drug ads claim, Hart observes, addiction "is not an equal-opportunity disorder." He notes that even rats, whose voracious consumption of cocaine in certain contrived conditions supposedly shows how powerfully addictive that drug is, tend to use it in moderation when they have other options, such as food, sex, or an interesting environment to explore.

Crack "gained the popularity that it did in the hood…because there weren't that many other affordable sources of pleasure and purpose," Hart writes. "And that was why, despite years of media-hyped predictions that crack's expansion across classes was imminent, it never 'ravaged' the suburbs."

Furthermore, Hart's own research with heavy crack smokers found that, in contrast with the stereotypical addict who cannot help but immediately consume whatever crack is available, they frequently rejected the drug in favor of small cash payments or vouchers. He got similar results with meth snorters, even though he deliberately recruited frequent consumers who had no interest in stopping. These findings underline a crucial truth that Hart emphasizes: "The effects of drugs on human behavior and physiology are determined by a complex interaction between the individual drug user and her or his environment."

Hart debunks various other misconceptions about crack and meth. He notes that the vast majority of violence attributed to crack grew out of black-market disputes, as opposed to the drug's pharmacological effects. His studies found that cocaine and methamphetamine do increase heart rate and blood pressure, but the effect of typical doses is not dangerous in otherwise healthy people. He argues that research linking meth to brain damage confuses correlation with causation and fails to show that meth users' cognitive capabilities are outside the normal range. And in case you were wondering, "There is no empirical evidence to support the claim that methamphetamine causes one to become physically unattractive."

Hart is well aware of the hostility he is apt to provoke by challenging the myths underlying the war on drugs. He describes a 2005 meeting with journalists, arranged by the Office of National Drug Control Policy, where he tried to put the dangers of methamphetamine in perspective, noting that the drug is a government-approved treatment for narcolepsy and attention deficit hyperactivity disorder (ADHD). He cited his own research finding that methamphetamine has "the same effects" as a more familiar ADHD drug, Adderall, which has a "nearly identical" chemical structure. He added that pilots and soldiers commonly use amphetamines to stay alert.

Yet for some reason amphetamine use in these contexts is not considered alarming, physically dangerous, dentally destructive, or apt to produce outbursts of irrational, murderous violence. Hart's calm and accurate presentation contrasted sharply with the tales of chemical slavery, degradation, and monstrous mayhem told by the other "experts" invited to the meeting: a cop, a prosecutor, and a self-identified meth addict. "My fellow panelists were horrified," he says.