Sensorics and Evolution

In the course of evolution, sensory tasks and functions were grouped around two relatively independent complexes of behavior.

The first is related to near space. This includes feeding behavior, self-care (in social animals, especially primates – also care for others), taste, smell, tactile perceptions, tasks of maintaining the body’s homeostasis (including temperature and pain sensitivity), as well as sensitivity to a number of internal organs, feedback from which is important for behavioral choice (stomach, bladder). Auditory perception, which evolved from vibrational-tactile perception, also belongs to this group.

The second, independent group of sensory tasks is that which is associated with distant space and serves the needs of hunting and competition. Here, vision plays the leading role. Se – it is about the distribution of objects in the surrounding space, assessment of their individual strength/power characteristics, assessment of their speed, direction of movement, distance to them. All hunting and power competition functions also require speed, accuracy in determining directions (precision), and physical endurance. It is these functions, which are essentially properties not of sensory organs, but of executive organs, that in practice turn out to be statistically closely correlated with purely sensory abilities related to Se. Those who are physically strong and motorically dexterous also turn out to be quicker than others at assessing the overall traffic situation – that is, whether it is possible to run across the road in a stream of moving cars, whether, while driving, one can attempt an overtake, and so on.

There is also a third, special group of tasks – memory of trajectories, i.e., usual routes of one’s movement. And here, although these tasks might seem more connected with vision, the leading role still belongs to Si. Because Se is a static function. Its visual work is about the here and now. But Si is adapted for remembering sequences of signals and actions, and route memory is built on that exactly.

When we, with our eyes closed, try to accurately touch the tip of our nose with a finger – this is a typical Si task, connected with the Si sensation of the internal map of one’s body and coordination of this map with the fine motor skills of our hands.

When we move through the labyrinths of our apartment with our eyes closed – that is also a typical Si-task. The map of near space is always closely linked with the map of one’s own body, with sensitivity to one’s position and orientation in space, and all this belongs to Si processing.

Determining the taste, olfactory, thermal, textural, and vibrational characteristics of objects – this is also Si.

Fine motor skills of the hands and fingers, from writing on paper and threading a needle to playing keyboard instruments – this is also Si.

Acts of swallowing, movements of the larynx during speech, sensitivity of all parts of the tongue – both to taste and bitterness, and to the texture of food, and even its reflex gag reaction when the root of the tongue is tickled – all of this belongs to the domain of Si.

And absolutely all of the listed Si signals are integrated in the same area of the brain – the posterior insular cortex, where the nerve pathways from muscles, internal organs, skin, and from the taste, smell, and auditory analyzers converge. There, the integration of all these signals takes place. But the typical visual and motor tasks of Se are not represented there. The corresponding nerves bypass the posterior insular cortex.

That is, the tasks of Si and Se turn out to be anatomically separated as well.

This is how evolution divided their functions, as it proved convenient for increasing the adaptive properties of vertebrate organisms.