Whether humans possess free will or whether their actions are determined by something outside their conscious control is one of the most persistent problems in philosophy.
In a lecture May 9, Steven E. Hyman warned his audience that he would not attempt to resolve the issue of free will in an ultimate sense. He did, however, have some fascinating insights regarding a special instance of the free-will dilemma — namely, the neurochemical mechanisms that result in the loss of free will when a person becomes addicted to drugs.
“Drug addiction has been used as a yardstick for reward-based behavior,” said Hyman. “With addiction, there is a narrowing of life focus in that drug-seeking crowds out all other motivations and goals.”
Hyman, University provost and professor of neurobiology at Harvard Medical School, has also served as director of the National Institute of Mental Health and was the first director of Harvard’s Mind, Brain, and Behavior Initiative. His talk was titled “Compulsion and the Brain: Subverting the Concept of Self-Control” and was given as the first Provostial Lecture, sponsored by the Humanities Center.
In his introduction, Humanities Center director Homi Bhabha noted that Hyman was one of the originators of the collaboration between the Humanities Center and the Harvard Stem Cell Institute that resulted in a series of public discussions under the heading “Between Two Cultures.”
Hyman began by explaining what neuroscience has learned about the process by which humans choose among multiple goals and direct their behavior toward obtaining their choices. The part of the brain that manages this process is the prefrontal cortex.
Scientists first began to gain an understanding of the role of the prefrontal cortex in 1848 with the case of Phineas Gage. Gage, a hardworking and conscientious railroad employee, was the victim of a freak accident in which an explosion drove a steel rod through his skull.
Gage survived the accident but seemed to undergo an abrupt personality change.
“He retained his intelligence, but he was no longer sober and reliable. He could no longer conform his behavior to specific goals,” Hyman said.
Scientists now believe that the rod destroyed Gage’s orbital prefrontal cortex, the part of the brain in charge of encoding goals and assigning relative value to them.
Scientists have since identified other structures that perform functions such as holding goals in mind, monitoring behavior necessary to obtaining goals, and resolving conflicts that arise over conflicting goals.
Another essential aspect of the process of seeking and obtaining goals is the dopamine system. Dopamine is a neurotransmitter secreted into the nerve synapse by the presynaptic terminal vesicles, then reabsorbed back into the nerve cells.
Experiments with laboratory animals have shown that the release of dopamine signals the brain to expect a reward. After the reward is obtained, dopamine returns to the nerve cell. Thus, under normal conditions, dopamine is only involved in the process of pursuing a reward, not in the enjoyment of it. But this process can be distorted by the use of drugs such as heroin, cocaine, and amphetamine.
“These drugs are Trojan horses,” said Hyman. “Each of them contains a chemical that is enough like the neurotransmitter that they increase the amount of dopamine in the brain.”
When dopamine continues to be released beyond the normal period, the brain is thrown into a perpetual state of “wanting,” which is the essence of addiction.
Long-term use of addictive drugs, Hyman said, creates processes in the nerve cells that “literally rewire the brain. The circuitry becomes deranged, which elicits automatic drug craving and drug seeking.”
These changes in the brain’s circuitry and the resulting loss of control over the normal goal-setting and goal-seeking process are what makes it so difficult for addicts to recover and return to normal lives.
“I’m not saying that these people are zombies,” Hyman said. “They can grab hold of themselves and regain control of their behavior, but they are at a high risk of relapse.”
What are the policy implications for this model of addiction? One of them, Hyman said, is that because the addicts’ brains are so compromised, it is necessary for others — families, friends, and institutions — to fill in and act almost like “a prosthesis” for the brain functions that are missing or disabled. In order to succeed, however, they must be “absolutely relentless,” added Hyman.
“Drug addiction is a very dramatic form of compulsion,” he said. “We are probably a little less in control than we’d like to believe we are.”
Nevertheless, Hyman believes that addicts should still be held responsible for their actions.
“The fiction that they are responsible may be what gets them to change their behavior,” he said. “A society that errs on the side of holding people responsible is better than a society that errs on the side of giving people excuses.”
There are actually clinically proven reasons for holding people responsible for their actions, Hyman said. Experiments have shown that people function better and are more able to deal with stress when they feel that they are in control.
“We are wired for personal responsibility, even if it’s a bit fictional.”
But “punitive moral opprobrium” and overly harsh prison sentences for minor drug offenses do not serve any useful purpose, Hyman added.