WHERE WE MEET THE WORLD

An overview of the five traditional senses, plus a few others.

“A sense can be defined as a faculty that detects a specific stimulus by means of a receptor dedicated to that stimulus,” writes Ward, director of the Animal Behaviour Lab at the University of Sydney and author of The Social Lives of Animals. Light activates receptors in the retina, and taste receptors “coat our tongues,” but nothing happens without the brain, which converts electrical impulses into our sensual experiences. Colors do not exist; we see “red” because that’s how the brain interprets certain electrical wavelengths. As the author shows, the brain evolved for survival, not accuracy. It can’t handle every sensory input, so it seeks patterns, takes shortcuts, cuts corners, and sees, hears, tastes, or smells what it expects on the basis of past experience. Ward devotes the most space to vision. “Sight involves a vast number of sensory receptors…and consumes more of the brain’s resources than all the rest of our senses combined,” writes the author. Despite writing and sign language, sound remains preeminent in human communication. A molecule becomes a smell or taste when it hits a receptor inside our nose or mouth, and smell is responsible for up to 80% of our taste. As the Covid-19 pandemic demonstrated, losing the ability to smell limits the pleasure of eating. Long before language evolved, touch was the primary means by which humans communicated, and it remains essential for taking in information on our surroundings and registering pain. It’s also the indispensable catalyst for relationships. We constantly touch those around us, and infants require touch to develop normally. Ward also notes how scientists have no doubt that other senses exist. Balance, for one, is no mean feat and requires its own specialized organ in the ear. Many animals sense Earth’s magnetic field in order to navigate, and Ward describes some studies that demonstrate its presence in humans.

Enjoyable popular science.