Surprising sounds could lead to riskier decisions

When you make a decision, certain neurons in your brain release short bursts of the neurotransmitter dopamine. A new Yale study shows that when other factors unrelated to the decision at hand, such as an unexpected noise, trigger these dopamine bursts, it can lead to riskier decision-making.

These findings demonstrate how the sounds around us can affect our choices and could also help researchers better understand dopamine systems in the brain and how they contribute to diseases like schizophrenia and depression.

The study was published on September 13 in Nature Communications.

“Many of us have an intuition that hearing an unexpected sound would be distracting, that it might lead to mistakes or loss of concentration,” says Robb Rutledge, assistant professor of psychology in the School of Arts and Sciences at Yale and senior author of the study. “But when we think about the neurobiology, we know that dopamine plays a role in decision-making, and that a surprising sound causes a brief surge of dopamine.”

That’s because the sound can signal something important, Rutledge explained, like something rewarding. When we make a decision, short bursts of dopamine may be involved, partly because the brain is evaluating how satisfying the options are.

Rutledge and Gloria Feng, a doctoral student in Rutledge’s lab and lead author of the study, wondered whether a surprising sound unrelated to a decision could nevertheless influence the decision, because of this shared dopaminergic action.

In a series of seven different experiments, the researchers tested this idea by assigning 1,600 people to a task in which they had to choose between a safe option and a risky option that offered different numbers of points. Before making their choice, participants heard a sequence of sounds. In the first experiments, participants heard six sounds in a row before each decision. But sometimes, the sixth sound in the sequence was different; the researchers called these sequences “rare” because they occurred only 25 percent of the time.

The researchers then looked at how these rare sequences affected the choices participants made.

“We found that surprising sensory events, these unexpected sequences of sounds, increased people’s risk-taking,” Feng said.

Specifically, participants chose the risky option an average of 4% more after hearing the rare sequence than after hearing the common sequence. They were also more likely to choose the option they had not chosen on the previous trial after hearing the rare sequence.

In additional experiments, the researchers played both sequences with the same frequency, eliminating both effects. The researchers also swapped the sequences so that the one that ended on a different note was played more often. In these experiments, the rare sequences did not increase risky decision-making, but they did increase the likelihood of changing choices compared to the previous trial.

“This shows that these two effects are separable, meaning there might be something different in the underlying neurobiology that causes them,” Feng said.

Although the increase in risk-taking wasn’t huge, Rutledge said, it was very consistent.

“Imagine an urban environment where there is so much noise that is mostly unrelated to our daily decisions,” he said. “Maybe these noises are influencing our decisions even when we don’t notice it.”

Rutledge wonders whether these effects are common in certain noisy environments like casinos.

“If a slot machine triggers at the right time, maybe a player sitting at a blackjack table has a 4 percent greater chance of making a riskier choice,” he said. “That can have a big effect at that moment and certainly cumulatively over time.”

Beyond decision-making, these results also hold promise for understanding the role of dopamine in the brain and its effect on mental illness.

Dopamine is implicated in many pathologies, Rutledge said, including psychosis in schizophrenia.

“Schizophrenia can be extremely devastating, and hallucinations can be very distressing for people who have it,” Rutledge said. “We have drug treatments for schizophrenia that block dopamine, but we need to do better. Similarly, some depression medications target dopamine, and it would be interesting to see if we could use that to understand the differences between people who respond better to dopamine or serotonin medications.”

While researchers have tools to study the dopamine system more precisely in animals, the tools available for use in humans are largely limited to pharmaceuticals that can alter dopamine levels over longer periods of time.

“By using sounds, we might be able to deliver small, temporary bursts of dopamine to humans,” Feng said. “This tool could help researchers better understand the effects of dopamine on the decisions we make.”