Summary: New research helps explain why people persist in using drugs despite knowing the risks, and why their drug-taking behaviour can be so difficult to change.
Source: University of Cambridge.
People addicted to cocaine are especially prone to forming rigid habits that make their behaviour resistant to change, even when those actions have harmful consequences, according to new research from the University of Cambridge. These findings shed light on why some individuals continue using drugs despite awareness of negative outcomes and why changing that behaviour can be so challenging.
“Addiction typically develops gradually, through repeated actions that eventually overpower voluntary control,” said Dr Karen Ersche of the Department of Psychiatry, who led the study.
Published in the journal Science, the study tested 125 adults—72 with cocaine addiction and 53 without a history of substance dependence—on tasks designed to measure habit formation and goal-directed control. The researchers found that people with cocaine addiction were far more likely than healthy participants to behave automatically when their responses had previously been rewarded. In other words, rewarded behaviours became automatic and continued even after they stopped producing the expected benefit.
By contrast, in a separate task where participants learned to act to avoid an unpleasant outcome (electrical shocks), those with cocaine addiction did not develop avoidance habits. In that context, addicted participants were less willing than control participants to exert effort to prevent the negative outcome in the first place.
“Our experiments show a double-edged pattern in cocaine addiction,” Dr Ersche explained. “When a behaviour has been rewarded—such as the pleasurable effects of using cocaine—addicted individuals form strong automatic routines and then struggle to modify them, even when consequences change. Yet when facing adversity, they appear less motivated to act to avoid harm.”
These results carry important implications for treatment. Traditional punitive approaches—threats of negative consequences—are unlikely to discourage drug use if the behaviour has become habitual. Instead, interventions that capitalize on the habit-forming tendency by training healthier, goal-directed routines to replace drug-taking habits may be more effective. The authors also suggest that people with cocaine addiction should be actively protected from harmful outcomes, since simple warnings or threats are unlikely to trigger avoidance.
The study used two complementary experiments to probe how training and outcome value influence behaviour. In the first experiment, participants learned associations between pictures and a correct response that earned points. After extended training, some pictures were devalued—no longer worth points. Compared with control participants, those with cocaine addiction were less likely to adjust their responses after devaluation and more likely to continue responding automatically despite the changed reward structure.
In the second experiment, participants learned to associate two pictures with an unpleasant stimulus—an electric shock. They were then instructed in a method to avoid the shocks by pressing a foot pedal. Individuals with cocaine addiction were poorer at learning to avoid the shocks initially—suggesting deficits in learning or motivational processes—and as a result did not develop strong avoidance habits.
Currently, there is no approved medication that reliably treats cocaine addiction; patients are commonly offered psychosocial and cognitive therapies. Dr Ersche says these findings point to alternative therapeutic strategies that might better address the specific behavioural profile seen in cocaine addiction. The research team plans to investigate the neural mechanisms behind heightened habit formation and reduced avoidance in cocaine users, with the aim of shaping more effective treatment approaches.
Funding: The work was supported by the Medical Research Council and took place at the NIHR Cambridge Biomedical Research Centre and the Behavioural and Clinical Neuroscience Institute.
Source: Craig Brierley – University of Cambridge
Image Source: This NeuroscienceNews.com image is in the public domain.
Original Research: Article published in Science: “Carrots and sticks fail to change behavior in cocaine addiction” by Karen D. Ersche and colleagues. Published online June 17, 2016 (doi:10.1126/science.aaf3700).
University of Cambridge. “’Carrots and Sticks’ Fail to Change Behavior in Cocaine Addiction.” NeuroscienceNews, 17 June 2016.
Abstract
Carrots and sticks fail to change behavior in cocaine addiction
Cocaine addiction creates persistent, maladaptive behaviour that is difficult to treat. This study identifies a pattern in which extended training enhances performance when actions are rewarded but simultaneously makes those actions insensitive to changes in outcome, producing inflexible, habitual responding. Conversely, extensive training does not improve avoidance behaviour in individuals with cocaine addiction: they show reduced avoidance learning and fail to develop protective habits. These findings illustrate why punitive or threat-based strategies are unlikely to succeed and highlight the therapeutic potential of interventions that strengthen goal-directed control and establish healthier, replacement habits in place of drug-taking.