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First evidence that human brain uses one code for space, time and social distance

Posted December 23, 2014

What is the relationship between space, time and social distances in the human brain? This question has long been the subject of philosophical inquiry and psychological experimentation. But now scientists from Department of Psychological and Brain Sciences, Dartmouth College, New Hampshire found evidence that people use the same brain circuitry to figure out all three previously mentioned concepts.

Human brain lobes. Image credit: Allan Ajifo via Flickr, CC BY 2.0

Human brain lobes. Image credit: Allan Ajifo via Flickr, CC BY 2.0

In previous studies researchers suggested that different domains of psychological distance are encoded similarly. They argued that we, humans, use spatial language to describe social and temporal relationships, such as „close friend“ or „distant cousins“, and to describe various distance words when we talk about time, for example, „the distant future“ or „a long meeting“, because we mentally represent this information in spatial terms. However, past studies didn’t use various analyses that spatially smooth and average data to identify human brain areas involved in processing different tasks.

Researchers now believe that they have found how exactly these figures of speech are rooted in our brain system.

In a new study, scientists examined fifteen participants aged 20-28 years, right-handed, fluent in English, who had normal or corrected to normal vision. All participants were presented with spatial, temporal and social distance trials which consisted of objects photographed at different egocentric distances, words and names which referred to the immediate or more remote future, and photographs of familiar others and acquaintances, respectively. They were asked to think about how much closer or farther, more or less familiar, or sooner or later the target was relative to the anchor during spatial, social, and temporal distance trials. This procedure was repeated using all possible combinations of distance domains for training and testing.

To see how this experiment affected participants’ brains, researchers used statistical pattern recognition techniques to identify human fMRI data. When participants evaluated their opinions and enjoyment of activities, fMRI magnitudes were expressed in brain areas which are associated with mental simulation. What was interesting and surprising is that all brain areas were influenced similarly by different distance domains.

The main activity was clustered within the right IPL (Inferior Parietal Lobule). This region is a part of a larger neural network called the frontoparietal control network (FPCN). In addition, the scientists discovered that the right IPL also engages the right temporal parietal junction (TPJ). Together, these two regions cooperate to help generate one’s unique sense of self. The right IPL seems to represent space radiating out from the self, while the right TPJ supports mental distinctions between one’s self vs. others.

Researchers also found that fMRI evidence was consistent with behavioral findings stating that different distance domains influence our thoughts and actions analogously. This evidence from social psychology and neuroscience demonstrated similar effects of different distance domains on cognition and behavior, consistent with suggestions that this information implies a common psychological meaning.

These results mean that for computational efficiency the human brain uses a common neural code to represent space, time and social “distance”. Objects, times and people who are considered “close” use one pattern of activity, while those which are considered “distant” activate a second.

The results of this experiment agree with Construal Level Theory which states that any form of distance means the same thing mentally, whether it’s a distance from the present moment or from a person’s own subjective experience. The authors of the study said that this study explains why we tend to talk about time and relationships using metaphors for physical distance – such metaphors mirror the neural processes occurring in our brains as we consider space, time or degrees of social connection.

Researchers believe that their research will be informative for future studies aimed at characterizing the relationship between space, time and social distances in human brain, and they are certain that such attempts will not be a trivial endeavor: studying health and evolution of our brain is closely related with studies of the general principles of human brain and human cognition.


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