Innocent people often falsely confess to crimes that they did not commit under increased stress of police interrogation even though they start by being less stressful compared to the guilty, a new study reveals.
To better understand what leads to false confessions, Max Guyll, an assistant professor of psychology, and Stephanie Madon, an associate professor of psychology, measured various indicators of stress, such as blood pressure, heart rate and nervous system activity.
It was found that stress levels increased for all participants when they were first accused. However, the levels for those wrongly accused were significantly lower. Researchers said that's a concern because it can make the innocent less likely to vigorously defend themselves in a real interrogation.
For students participating in the ISU study, it took only a short amount of time for some to confess. Students were connected to monitors so that researchers could measure their stress levels at different points throughout the experiment.
Madon said the students were given an assignment, part of which was to be completed individually and the other part with a partner. The experiment was set up so that the partner would ask some students for help with the individual task, essentially getting them to break the rules, so they would be guilty of misconduct.
Students, both innocent and guilty, were later accused of academic misconduct and asked to sign a form confessing. It came as no surprise to researchers that 93 percent of the guilty students confessed, but 43 percent of those who were innocent also agreed to sign the confession form.
Although the innocent showed less stress than the guilty when first accused of misconduct that changed when students were pressured further to sign a confession. In comparison to students who gave up and confessed, the innocent who refused to confess showed greater sympathetic nervous system activity, which is associated with the fight or flight response.
If questioned for a long period of time, the greater expenditure of resources could start to take a toll, Guyll said. And as a result, cause even more of the innocent to lose their energy and motivation to continue defending themselves, ultimately leading them to give up and confess.
The study is published in journal Law and Human Behaviour.