Is that guilt in your gut? How your body changes when experiencing guilt compared to other emotions.
How do you know when someone feels guilty? Can you see it in their face? How about in their body language or behaviour? Is there a way to “detect” guilt? Lie detectors (formally polygraphs) were at one time a common tool used in the legal system, sometimes as evidence in favour of a witness’s credibility, and other times to coerce an arrested individual into confessing. However, their usage as admissible evidence during criminal trials in Canada was halted following a judgment made by the Supreme Court of Canada during the 1987 R v. Béland case.
The reasons cited by the supreme court were legal in nature. However, the greater scientific field has questioned the legitimacy of polygraphs for a long time. In fact, one report from 2003, and a revisitation of the same topic in 2019, concluded that the validity (i.e., the degree to which a tool measures what it is thought to measure) of polygraphs is very poor, and is based on low quality scientific research.
One inherent flaw of the polygraph often goes unrecognized; asking someone to undergo a polygraph test may inadvertently cause their body to start showing changes that appear to reflect feelings of guilt. In reality, they might just be feeling anxious, stressed, or nervous. While we can’t determine if an individual is telling the truth using polygraph testing, there are ways to objectively measure changes in our bodily activities that occur when feeling different emotions.
In 2023, an experiment conducted at the University of Western Ontario explored whether guilt, compared to other basic emotions like sadness or amusement, is associated with distinct patterns of changes occurring in the body. Using psychophysiology (i.e., measuring how changes in the body relate to or correlate with psychological processes and vice versa), they measured changes in heartbeat, swallowing, and stomach muscle activity when healthy participants watched videos designed to elicit varying emotions.
Through this study, the researchers were able to demonstrate that there were distinct patterns of changes in the body that occurred when participants felt guilty, as opposed to when they felt other basic emotions such as amusement, pride, or no emotion at all. Contrary to popular media tropes of a “guilty gulp” (e.g., when a character in a television show is being interrogated and is guilty or nervous and makes a loud “gulp” sound), the study showed that when feeling guilty participants rate of swallowing actually decreased compared to when they felt sad or disgusted.
Further, guilt could be distinguished from other emotions by measuring the rate at which a person was sweating. Compared to amusement, pride, and sadness, participants sweat less when feeling guilty. This was an unexpected result; the researchers had hypothesized that sweating would be greater during guilt compared to other emotions, because guilt has been thought to be an intense and motivating emotion.
Lastly, changes in activity of an individual's stomach contractions were the only measure that distinguished guilt from all other emotions measured in the study (amusement, disgust, pride, sadness, no emotion). Compared to guilt, all other emotions were associated with an increase in the rhythm that the stomach contracted.
Although the results of the study suggest that these measures are an effective way of describing what is going on in the body when people are feeling various emotions, this does not mean that in turn we can use them to determine whether an individual is guilty.
Overall, this study provided foundational work for understanding guilt and how it can be measured via changes in the body. The researchers suggest future experiments should explore what these patterns of bodily changes look like in individuals with a mental illness, such as post-traumatic stress disorder or obsessive-compulsive disorder, as these disorders often feature heightened feelings of guilt compared to a typical individual.
Original Article: Stewart, C. A., Mitchell, D. G. V., MacDonald, P. A., Pasternak, S. H., Tremblay, P. F., & Finger, E. (2023). The psychophysiology of guilt in healthy adults. Cognitive, Affective & Behavioral Neuroscience, 23(4), 1192–1209. https://doi.org/10.3758/s13415-023-01079-3