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People who are addicted to cocaine are bad at changing acquired behaviours and slow to avoid adversity, according to a study conducted by an international team of psychologists including Sanne de Wit of the University of Amsterdam and Maartje Luijten of the Radboud University. Their findings, published in the latest volume of Science, offer new guideposts for the treatment of addiction.

Flickr CC, Valerie Everett
Credits: Flickr CC, Valerie Everett

Cocaine use starts with a snort and the euphoric high that follows. Over time, however, use can become an addiction, with ensuing health and financial problems and estrangement from family and friends. To study the effect of rewards and penalties on habit development in the lab, the researchers selected 72 test subjects with cocaine addiction and a control group of 53 people with no addiction.

From losing points to electrical shocks

In their first experiment, subjects were instructed to press a button as quickly as possible after seeing an image appear on a screen. Points were awarded for each correct and rapid response. After 15 minutes of practise, the conditions were changed. Now, when certain images were presented, pressing a button led instead to a deduction of points. Addicts had significantly more difficultly in suppressing their habituated response of pressing the button when there was no reward. They continued to press the button even when doing so had a negative consequence.

In a second experiment in which the test subjects were shown a new set of pictures, the presentation of certain pictures was paired with a mild electrical shock. To avoid the shock they had to press a foot pedal when shown that image. The test subjects with a cocaine addiction were less inclined to press the pedal to avoid a negative outcome.

Automatic pilot

The study, led by University of Cambridge psychologist Karen Ersche, sheds new light on the rigidity of behaviour in addicts. Though initially highly responsive to rewards, they find it difficult to change their habits when faced with changed circumstances. Instead, says De Wit, ‘They tend to switch to the autopilot of habit’.

This inclination to develop habits and apathy in the face of penalties may be harnessed for more effective addiction treatments. In many cases, focusing on the negative consequences of addiction – warnings like ‘if you don’t quit, you’ll lose your job’ – may not be helpful. According to De Wit, ‘On the contrary, it creates stress, which past studies have shown causes people to revert to old habits’.

More promising, believes De Wit, would be interventions that target addicts’ proneness to developing habits by replacing the drug addiction with another, positive habit. ‘Seeking the company of other people such as family and friends or playing a sport as an alternative to using drugs, for instance.’ Another fruitful approach is to reward non-drug use. This technique is already used in contingency management, a form of therapy, where people with an addiction can earn vouchers for activities they enjoy, such as gym and restaurant visits, through abstinence. This approach therefore reinforces the desired behaviour.

Alcoholism in animals

Does addicts’ behavioural rigidity stem from the neurotoxic effects of their drug use, or is their addiction rooted in their inclination to develop habits? On the basis of this study, it is impossible to say, asserts Luijten. ‘To test that, you would have to track a group of people over many years and then in those who end up with an addiction look at what developed first, the drug habit or an overall rigidity in behaviour. Studies done on alcoholism in animals suggest an interaction between these two factors. The inclination to develop habits makes the animal prone to addiction, which in turn makes it even more inclined to develop habits.’

Luijten is currently doing a follow-up study in which young people are being tracked over a longer time span to examine if a similar rigidity is at work in the development of nicotine addiction. De Wit is researching the development of eating habits and how they can be broken.

Publication details

Karen Ersche, Claire Gillian, P. Simon Jones, Guy Williams, Laetitia Ward, Maartje Luijten, Sanne de Wit, Barbara Sahakian, Edward Bullmore, Trevor Robbins. ‘Carrots and sticks fail to change behavior in cocaine addiction’. Science; 17 Jun 2016; DOI: 10.1126/science.aaf3700