New research suggests your ability to forgive—or not—is actually biological

Forgive and forget is advice easier for some people to follow than others. But a newly published neuroscience study has given those who hold onto grudges a good excuse: It seems the ability to forgive is linked to the size of a specific area in the brain.

The research, published in Scientific Reports earlier this month, is based on brain-imaging scans of a limited sample size of 50, so the results are not definitive. But the study does suggest a connection between how we assign blame and the size of the anterior superior temporal sulcus (aSTS) in our brains.

Researchers from Boston College in Massachusetts, Trieste University in Italy, and the University of Vienna in Austria conducted the study by presenting participants with various scenarios, and asking them how much blame the people in the scenarios deserved.

The scientists gave information about both the intentions of the agents in the scenarios, and the consequences of their actions. The study participants were asked to answer two questions on a scale from 1 to 7: “How morally acceptable was [the agent]’s behavior?” and “How much blame does [the agent] deserve?”

There was high correlation between how participants answered the two questions—i.e., those who answered the first with a high number, also answered the second with a low number. The researchers combined the scores to indicate each subject’s “severity of moral condemnation.” Those who showed highly severe moral condemnation were essentially more likely to blame an agent for their actions, even if their intentions were innocent and any harmful consequences purely accidental.

The researchers used fMRI and MRI scans to monitor brain activity while the subjects were answering the questions, and so were able to identify brain differences in those who were more forgiving of innocent mistakes. They found that, “the greater the gray matter volume [in the left aSTS], the less accidental harm-doers are condemned.” This area of the brain is linked with our ability to understand others’ motives (known as “mental-state reasoning”).

Indrajeet Patil, the study’s first author, says the research suggests some people are biologically predisposed to forgiveness. Though the relationship between brain area and function is still unclear, it’s generally believed that more gray matter is linked to greater performance of that region. For example, one study found that London taxi drivers have more gray matter in certain areas of the hippocampus linked with navigation skills. “Individuals who have more gray matter [in the left aSTS], so the argument goes, rely more on reasoning about innocent intentions while judging accidents, and so forgive actors involved in such situations,” Patil writes in an email.

Patil notes that the capacities for both forgiveness and the condemnation can be useful. “If your trusted friend accidentally damages your property, it helps to have the capacity to reason about their innocent intentions lest we forfeit a valuable social partner by obsessing over only the bad outcome,” says Patil. “On the other hand, our ability to think about others’ thoughts can also help us protect from individuals with malevolent intentions, like breaking ties with a colleague who unsuccessfully attempted to sabotage your promotion by bad-mouthing you.”

Stuart Ritchie, a psychologist at University of Edinburgh who was not involved in the study notes that, though the research is well conducted, the sample size is small. MRI scans are expensive, he notes, which often limits sample size, but he cautions against “drawing any really strong conclusions.” The paper’s authors also note that future studies could focus on other demographic details, such as personality traits, education, and ethnicity, and how these affect the findings.

Further research is needed but, should the initial findings hold up, that doesn’t mean our inclination to forgive is permanently fixed. Patil notes that studies suggest training can enhance our ability to understand and reason about other’s mental states. So, even those who are predisposed to cast blame can eventually learn to forgive.

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