Tags : science
New Finding Uncovers Part Of Brain Determining Acceptable Social Personal Space
Pasadena, CA (AHN) – In a finding that sheds new light on the neural mechanisms involved in social behavior, neuroscientists at the California Institute of Technology (Caltech) have located the brain structure responsible for our sense of personal space.
The discovery published in the latest issue of the journal Nature Neuroscience, can lead to new insight for autism related studies and other disorders where social distance is an issue.
The structure, the amygdala-a pair of almond-shaped regions located in the medial temporal lobes-was previously known to process strong negative emotions, such as anger and fear, and is considered the seat of emotion in the brain. However, it had never been linked rigorously to real-life human social interaction.
The research team, led by Ralph Adolphs, Bren Professor of Psychology and Neuroscience and professor of biology and postdoctoral scholar Daniel P. Kennedy, were able to make this link with the help of a unique patient, a 42-year-old woman known as SM, who has extensive damage to the amygdala on both sides of her brain.
Kennedy said in a statement, “SM is unique, because she is one of only a handful of individuals in the world with such a clear bilateral lesion of the amygdala, which gives us an opportunity to study the role of the amygdala in humans.”
The patient also has difficulty recognizing fear in the faces of others, and in judging the trustworthiness of someone, two consequences of amygdala lesions that Adolphs and colleagues published in previous studies on the subject. However during the years of studying the patient researchers noticed her outgoing nature was almost too friendly. She often violated people’s personal space when interacting with them.
During his years of studying her, Adolphs also noticed that the very outgoing SM is almost too friendly, to the point of “violating” what others might perceive as 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,” says Kennedy.
What makes this finding novel however is that previous studies of humans never had identified an association between the amygdala and personal space. However, SM’s unusual social behavior prompted a further investigation.
Adolphs, Kennedy, and their colleagues devised a simple experiment along with functional magnetic resonance imaging to quantify and compare her sense of personal space with that of healthy volunteers. The experiment used what is known as the stop-distance technique. Briefly, the subject (SM or one of 20 other volunteers, representing a cross-section of ages, ethnicities, educations, and genders) stands a predetermined distance from an experimenter, then walks toward the experimenter and stops at the point where they feel most comfortable. The chin-to-chin distance between the subject and the experimenter is determined with a digital laser measurer.
Among the 20 other subjects, the average preferred distance was .64 meters-roughly two feet. SM’s preferred distance was just .34 meters, or about one foot. Unlike other subjects, who reported feelings of discomfort when the experimenter went closer than their preferred distance, there was no point at which SM became uncomfortable; even nose-to-nose, she was at ease. Furthermore, her preferred distance didn’t change based on who the experimenter was and how well she knew them.
“Respecting someone’s space is a critical aspect of human social interaction, and something we do automatically and effortlessly,” Kennedy says. “These findings suggest that the amygdala, because it is necessary for the strong feelings of discomfort that help to repel people from one another, plays a central role in this process. They also help to expand our understanding of the role of the amygdala in real-world social interactions.”
The researchers believe that interpersonal distance is not something we consciously think about, although, unlike SM, we become acutely aware when our space is violated. With humans interpersonal distance varies cross-culturally and researchers believe that cultural preferences and experiences affect the brain over time and shapes how it responds in particular situations.
The findings may have relevance to studies of autism in that the disease affects an individual’s ability to interact socially and communicate with others.
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