Your moral compass can be influenced more than you think. A new study published in Current Biology shows that using two common drugs, an antidepressant and a treatment for Parkinson’s disease, can help sway moral decisions.

The researchers randomly designated the subjects as “deciders” or “receivers,” while all the participants were given an electric shock based on their own individual pain thresholds. Deciders were to go into rooms by themselves and take part in 170 trials. Within each trial, the subject could choose from different amounts of money for a certain amount of shocks, up to 20 shocks and 20p (pence) per trial. By the end of the experiment, either the subject received an electric shock or the decision-maker got shocked, with the decision-maker getting paid either way.

The experiment randomly selects half of the group to receive the serotonin-enhancing antidepressant citalopram while the other group received levodopa, a dopamine-enhancer. Levodopa is commonly used to treat Parkinson’s disease. Each of the groups that received medication also were compared against groups who were receiving a placebo. The researchers were surprised by the potential of the findings. The goal of the experiment was to create a real life decision-making process with real consequences in order to see how these specific drugs affect behavior.

“The central message is we need to have more research into how these drugs affect behavior, both in healthy people and in people taking them for disorders,” Molly Crockett, the lead author of the research and neuroscientist at the University of Oxford told The Guardian.

In a previous experiment that was conducted by the same team, the results showed that people disliked harming others more than harming themselves. This is behavior referred to as “hyper-altruism,” a term that another study from April of 2015 states is a trait that most people have.

That was on display for this study as well. On average, the people given a placebo were prepared to pay 35p per shock to prevent harm to themselves and 44p per shock to prevent it in others. Participants who were given the citalopram were willing to pay an average of 73p per shock to prevent harm to others. Conversely, those who were given the drug levodopa were prepared to pay approximately 35p per shock to prevent harm to others or themselves, meaning that they delivered an average of 10 more shocks to others during the experiment. This gives the impression that the participants who took the drug levodopa were on average more selfish than the participants who took citalopram.

What the study also seems to indicate is that while on average most people wouldn’t inflict harm on others, with the common drug citalopram, participants were more empathetic toward other people’s pain. Lest anyone think that this study can have negative ramifications, as though serotonin-enhancing medications would begin to be doled out to everybody to “force” them to be more empathetic, this study actually might be groundbreaking for the ways in which we can treat people with mood or behavioral disorders.

“Our findings have implications for potential lines of treatment for antisocial behavior, as they help us to understand how serotonin and dopamine affect people’s willingness to harm others for personal gain. We have shown that commonly-prescribed psychiatric drugs influence moral decisions in healthy people, raising important ethical questions about the use of such drugs,” Crockett said in a statement.

Source: Crockett M, Siegel J, Kurth-Nelson Z, et al. Dissociable Effects of Seratonin and Dopamine on the Valuation of Harm in Moral Decision Making. Current Biology. 2015.