Prescription Drugs Could Influence Moral Decisions

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Would you be willing to endure a bit of pain for cash? Most likely. But what about inflicting pain on others for a reward? Our choices in moral decisions like these can be influenced by a variety of factors, such as the situation in which they arise or what others around you are doing. Fascinatingly, a new study has suggested that moral decisions could even be influenced by medication.

During an experiment, people given a common anti-depressant paid significantly more to avoid harm to themselves or others than those in the placebo group. Conversely, a drug used to treat Parkinson’s reduced selflessness, meaning they wouldn’t favor harming themselves over others.

This is interesting because earlier work suggested that levels of the brain chemicals influenced by the drugs used in this study, serotonin and dopamine, might influence aggression or antisocial behavior, in which aversion to harming others is disturbed.

For the investigation, scientists from University College London and University of Oxford set out to examine whether an altruistic disposition displayed by most people – a greater aversion to inflicting pain on others rather than themselves – could be influenced by certain signaling molecules, or neurotransmitters. To do this, they observed how much pain people were willing to dish out in return for money.

Of the 175 healthy adults enrolled, 89 were randomly assigned either a placebo or the antidepressant citalopram, which influences serotonin levels, and 86 were randomly chosen to receive a placebo or levodopa, a drug used to raise dopamine levels in patients with Parkinson’s.

Participants were then randomly assigned one of two roles, a decider or a receiver, and anonymously paired up. Deciders were then isolated and given 170 different trials in which they had to decide how many mildly painful electric shocks would be dished out by the experimenters. For example, they could choose to select 7 shocks in return for £10 ($15), or 10 shocks for £15 ($23). Half of the scenarios involved self-harm, but in the other half the receiver was given the shocks. But in all of the trials, the decider was the one who ended up with the cash.

The researchers didn’t act out every single scenario, but one of the results was randomly selected to be implemented at the end, so the decision-makers knew that the situation was not entirely hypothetical and thus had real consequences.

As described in Current Biology, they found that the majority of people behaved altruistically, displaying a preference for self-harm rather than harm directed at others. Those in the placebo groups were willing to forgo, on average, about 35p ($0.54) per shock to prevent self-harm and 44p ($0.68) for harm to others. Citalopram, however, seemed to make people much more averse to harm, willing to pay around twice as much per shock to prevent harm. They still paid more to prevent harm to others, but interestingly this altruistic tendency was not seen in those given levodopa.

Those in this group were willing to forfeit an average of 35p ($0.54) per shock, whether that was to prevent self-harm or harm to others. They also spent less time deliberating on the number of shocks to be divvied out to others than those in the placebo group.

While the findings may therefore provide further insight into the underlying neural mechanisms for such behaviors, it’s necessary to note that the study has a serious limitation: Only healthy subjects were involved. We therefore have no idea whether the drugs are capable of influencing moral decisions in those who take the drugs for medical reasons, so it’s important not to demonize them on the basis of these results. 

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