Subjects: R and D
Cal Tech scientists may have figured out why some people have a notably annoying tendency to get too close during conversations, on subway trains or in restrooms.
The culprit turns out to be a malfunction in an almond-sized structure known as the amygdala, which is located in both temporal lobes of the brain. The amygdala processes negative emotions like anger and fear, but its role in social interaction had not previously been studied.
Daniel Kennedy, Ralph Adolphs and colleagus made the association by studying a 42-year-old woman known as SM, who has severe, isolated damage to her amygdala.
The scientists had known that SM couldn’t recognize fear in the expressions of others, or judge their trustworthiness, and had shown these abnormalities to be caused by her amygdala lesions.
While observing SM over time, Adolphs also noticed that she seemed to be too friendly, and frequently violated what others perceived to be their own personal space.
“She is extremely friendly, and she wants to approach people more than normal. It’s something that immediately becomes apparent as you interact with her,” Kennedy told BurrillReport.
So the scientists decided to compare SM’s sense of personal space to normal volunteers using the stop-distance technique, in which subjects approach a person until they reach a point where they feel most comfortable, and this distance is recorded.
Among the normal volunteers, the mean preferred distance was about 2 feet, but SM came in much tighter than that, about a foot. And unlike normal subjects who reported feeling uncomfortable when the experimenter approached to a distance within their preferred range, SM never became uncomfortable.
Even cheek to cheek, she was relaxed, and her feelings changed not a whit regardless of who the experimenter was or how well she knew them.
The write-up appears in Nature Neuroscience.