People who have damage to a specific part of their brains are more likely to be impulsive, and new research has found that damage also makes them more likely to be influenced by other people.
In a new study published in PLOS Biology, a research team found that damage to distinct parts of the medial prefrontal cortex (mPFC) were linked to being influenced by impulsive decision making by others, while another region was causally linked with choosing a smaller reward earlier rather than waiting for a larger prize.
The team from the University of Birmingham, University of Oxford and Julius-Maximilians-University Würzburg worked with participants with brain damage to assess whether they were more likely to be influenced by other people's preferences.
The team worked with 121 participants, with 33 having focal damage to the mPFC, 17 with lesions elsewhere on the brain and 71 participants who had no brain damage but were of the same age. The researchers showed participants a series of choices to test how impulsive people were in general. They were then presented with the same choices and shown what other people would pick, some of these people made very impulsive choices and some people made more patient choices.
Those participants with mPFC damage were more impulsive in general. The team were also surprised to find that those participants were also more likely to be influenced by other people who were impulsive, much more so than people who behaved patiently.
Professor Patricia Lockwood from the University of Birmingham and senior corresponding author of the study said:
"The results are important as every day we learn about what other people want, and this impacts on our own preferences for what we want. We used an experiment where we could look at whether it was when people behaved more impulsively, or if they were restrained, that social influence occurs.
"We find it is specifically a part of the brain that if its damaged makes you more influenced by others who behave impulsively, not when they behave in a way that is more restrained. We also find brain damage to a different part makes you more impulsive in general, even before you have been influenced by someone else.
"Together, our study shows that being influenced by others has a specific neural basis which could have implications for everything from how we understand misinformation and how other people can change our own financial preferences."
Patience
The team also used a combination of mathematical modelling and existing brain scans to map the size and location of lesions in the medial prefrontal cortex. The results suggest that specific impulsive influences are driven by the different regions of the mPFC.
Lesions in the dorsomedial section, which sits towards the top of the prefrontal cortex (PFC) were shown to have had the most significant impact on the social influence on impulsivity. Meanwhile, lesions on the ventromedial section lower down in the PFC were found to have a greater impact on being impulsive in general, before social influence.
Zhilin Su from the University of Birmingham and a lead author of the study said:
"We were able to work with a large sample of participants with an uncommonly specific damage to the medial prefrontal cortex. This gave us an opportunity to very specifically look at whether this damage might affect how influenced people are by others. We found that after damage people could still learn about other people's preferences, but they were also much more influenced by them."
