Everyday language often speaks of people carrying emotional baggage, and it’s seldom light: when we feel guilty, we say we feel heavier, our conscience “weighed down.” Only once we repent does it feel like a weight has been lifted from our shoulders. Often, the turn of phrase is only an offhanded idiom, but could this idiom in fact have real cognitive roots?

Scientists at the University of Waterloo and Princeton University seem to think so. Their recent study into feelings of heaviness, in the face of past transgressions, adds to a mountain of research into the power of suggestion — subjective, physical sensations that stem from real-world interactions or contexts.

“Guilt is important because it plays a role in regulating our moral behavior. It can help us correct our mistakes and prevent future wrongdoing,” researchers Dr. Romona Bobocel and Martin V. Day told Science Daily. “Of course, people know that guilt feels unpleasant and is sometimes associated with feelings of tension and regret.”

Day and Bobocel performed four studies in total to assess guilt’s physiological effects.

The first study asked participants to recall a moment in their past when they did something either ethical or unethical. The unethical moment could include lying, stealing, cheating — anything that would stir up feelings of guilt in the subjects. The team then had each person consider, on a scale of 1-11, how much lighter or heavier they felt after recalling their moral slip-up. To avoid guiding subjects toward the heavier end, they briefed them by saying people often report both differences.

Overall, subjects who remembered an unethical moment reported feeling heavier than the control and ethical groups.

“Notably, these findings remained strong regardless of participants' physical weight,” the team wrote, suggesting that the change in perceived heaviness is relative only to the guilty party.

The second and third studies sought to deepen the researchers’ understanding of guilt by tasking subjects with recalling the unethical deeds of others, and keeping personal memories concise. Both studies upheld the researchers’ original prediction, that guilt manifests itself in subjective feelings of weight.

The final study, however, was arguably the most lucid demonstration of the popular idiom made visible.

Subjects were asked to judge how much effort, on a similar scale as the first three studies, would be required to perform a given set of pro-social tasks. These were both physical and non-physical. Physical tasks included carrying groceries upstairs for someone, helping someone move, and carrying someone’s laundry. Non-physical acts included giving someone spare change, donating online, and holding the elevator for someone.

As predicted, “the same manipulation that instilled perceptions of weight related to guilt in our earlier studies was also found to affect judgments of effort for completing physical, but not nonphysical tasks,” the researchers wrote.

These findings are of particular note because they uphold what cognitive science has observed time and time again: people’s physical environment works in tandem with their subjective feelings and perceptions.

One MIT study found participants who assembled a puzzle with pieces that were covered in sandpaper reported social interactions not going as smoothly as people who assembled a normal puzzle. Another famous study from Yale University showed that people’s perceptions of others’ “warmth” or “coldness” was largely based on whether the person doing the judging was holding hot or iced coffee.

"Overall, it was exciting to find these patterns of results, which are consistent with an embodied theory of emotion,” Day and Bobocel told Science Daily. “Such results are encouraging, and hopefully this emerging line of research will lead us to a more comprehensive understanding of the nature of guilt."

Source: Bobocel R, Day M. The Weight of a Guilty Conscience: Subjective Body Weight as an Embodiment of Guilt. PLoS ONE. 2013.