Imagine waiting in line for a shot when someone who just got one tells you it was really painful. Could hearing that make the shot hurt more? According to a new Dartmouth study, what others say about an experience can shape how it actually feels.
The findings, published in the Proceedings of the National Academy of Sciences , show that social information can influence how people experience negative events from physical pain to watching others in pain and performing mentally demanding tasks.
"Our results suggest that when expectations are shaped by social information, people tend to hold onto those expectations which in turn impacts how we feel in a long-lasting way," says Aryan Yazdanpanah, a Guarini PhD candidate in the Department of Psychological and Brain Sciences and an Innovation PhD Fellow at Dartmouth.
To examine how social information affects perceptual judgements and learning, the researchers conducted an experiment in which participants were asked to complete three different tasks, each of which featured a similar sequence of events.
First, they received social cues by viewing dots on a computer screen which they were told represented how painful or mentally challenging the 10 previous participants had rated the activity.
In fact, the dots were just randomized and independent of the stimulus intensity.
Participants were asked about their expectations of pain or mental effort or to evaluate others' pain and were then exposed to the stimuli.
The three tasks included: an "experiential pain task" in which heat was applied to a participant's arm to create a painful but not harmful condition; a "vicarious pain task" of watching videos of others in pain such as that of a person's face grimacing; and a "cognitive effort task," for which participants had to mentally rotate images of two 3D objects and determine if they were identical.
In the pain domain, when people were told that others found an experience very painful, they tended to feel it that way themselves, even when they were in fact receiving a low level of heat. This effect was also evident when participants watched others in pain.
"These findings have important implications for how people interpret others' experiences. For example, if a person is truly in severe pain but others believe that the pain is not serious, this social belief may lead you to underestimate or overlook that person's suffering," said Yazdanpanah. "Similarly, when others describe an activity such as solving math problems as highly effortful, people may experience the same task as more mentally demanding."
Using behavioral analysis and computational modeling, the researchers determined that two mechanisms driving this behavior are confirmation bias in learning and the coloring of one's perception by expectation.
"We found that a person will favor the evidence that aligns with their beliefs but will ignore or dampen those which do not align," said Alireza Soltani , an associate professor of psychological and brain sciences at Dartmouth, whose work researches the neural processes that drive decision-making and learning.
This behavior demonstrates what is known as "confirmation bias in learning," and was illustrated across the study.
A second mechanism can make these beliefs difficult to update–when perception is colored by expectations. Consider a common example in back-pain recovery. "A person who has experienced back pain may expect that bending will cause pain," says Yazdanpanah. "Even if the body has physiologically healed and bending is safe, this expectation can increase the pain that is experienced. As a result, movements that are actually safe may still feel painful, weakening the very signal needed to update those beliefs."
In today's hyperconnected world where experiences are widely shared through social networks such information may shape expectations on a much larger scale.
"Our findings may offer insight into why expectations can persist even without evidence to support them," says Tor Wager , the Diana L. Taylor Distinguished Professor of Neuroscience at Dartmouth, whose lab studies the neurophysiology of pain and other affective processes. "The dynamics we observed can create self-fulfilling prophecies–feedback cycles that affect many kinds of health conditions, including chronic pain and fatigue, as well as beliefs about other people."
Wager and Soltani served as co-senior authors of the study. Heejung Jung, Guarini '24, a postdoctoral researcher at Stanford University who was a graduate student in psychological and brain sciences at the time of the study, also contributed to the research.
