Metaphor, Exaptation and Harnessing

We are used to the metaphor of time being related to distance, as in “back in the 1930s” or “it was a long day”. And there is a noticeable metaphor relating social relationships to distance, as in “a close friend” or “distant relatives”. But these are probably not just verbal metaphors, figures of speech, but much deeper connections. Parkinson (see citations below) has studied the neurobiology of this relationship and shows it is likely to be an exaptation, a shift in function of an existing evolutionary adaptation to a new or enlarged function. We have an old and well established brain system for dealing with space. This system has been used to also deal with time (rather than a new system being evolved), and later further co-opted to also deal with social relationships.



What spatial, temporal and social perception have in common in this system is that they are egocentric. Space is perceived as distances in every direction from here, with ourselves in the ‘here’ center. In the same way we are the center of the present ‘now’. We are also at the center of a social web with various people at a relative distance out from our center. Objects are placed in the perceptual space at various directions and distances from us. Events are placed various distances into the future or past. People are placed in the social web depending on the strength of our connection with them. It appear that with a small amount of adaptation (or learning) almost any egocentric system could be handled by the basically spatial system of the brain.



Parkinson has looked at the regions of the brain that process spatial information to see if and how they process temporal and social information. The paper has details but essentually, “relative egocentric distance could be decoded across all distance domains (spatial, temporal, social) … in voxels in a large cluster in the right inferior parietal lobule (IPL) extending into the posterior superior temporal gyrus (STG). Cross-domain distance decoding was also possible in smaller clusters throughout the right IPL, spanning both the supramarginal (SMG) and angular (AG) gyri, as well as in one cluster in medial occipital cortex”.



These findings provide preliminary support for speculation that IPL circuitry originally devoted to sensorimotor transformations and representing one’s body in space was “recycled” to operate analogously on increasingly abstract contents as this region expanded during evolution. Such speculations are analogous to cognitive linguists’ suggestions that we may speak about abstract relationships in physical terms (e.g., “inner circle”) because we think of them in those terms. Consistent with representations of spatial distance scaffolding those of more abstract distances, compelling behavioral evidence demonstrates that task-irrelevant spatial information has an asymmetrically large impact on temporal processing .” As well as the similarity to the linguistic theories of Lakoff and Johnson, this is also similar to Changizi’s ideas of cultural evolution harnessing the existing functionality of the brain for new uses such as writing.



Here is the abstract of the Parkinson 2014 paper:


Distance describes more than physical space: we speak of close friends and distant relatives, and of the near future and distant past. Did these ubiquitous spatial metaphors arise in language coincidentally or did they arise because they are rooted in a common neural computation? To address this question, we used statistical pattern recognition techniques to analyze human fMRI data. First, a machine learning algorithm was trained to discriminate patterns of fMRI responses based on relative egocentric distance within trials from one distance domain (e.g., photographs of objects relatively close to or far away from the viewer in spatial distance trials). Next, we tested whether the decision boundary generated from this training could distinguish brain responses according to relative egocentric distance within each of two separate distance domains (e.g., phrases referring to the immediate or more remote future within temporal distance trials; photographs of participants’ friends or acquaintances within social distance trials). This procedure was repeated using all possible combinations of distance domains for training and testing the classifier. In all cases, above-chance decoding across distance domains was possible in the right inferior parietal lobule (IPL). Furthermore, the representational similarity structure within this brain area reflected participants’ own judgments of spatial distance, temporal soon-ness, and social familiarity. Thus, the right IPL may contain a parsimonious encoding of proximity to self in spatial, temporal, and social frames of reference.

Parkinson C, Liu S, & Wheatley T (2014). A common cortical metric for spatial, temporal, and social distance. The Journal of neuroscience : the official journal of the Society for Neuroscience, 34 (5), 1979-87 PMID: 24478377

Parkinson C, & Wheatley T (2013). Old cortex, new contexts: re-purposing spatial perception for social cognition. Frontiers in human neuroscience, 7 PMID: 24115928

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