What makes sense?

We can only know the world around us by the context in which we sense it, both as individuals or even as species. Literally—individual humans with the five senses that are typical of our species can only perceive the world within the parameters of those senses. Individuals vary with respect to their sensory abilities, of course, as some persons are blind, others have compromised hearing, and others are the so-called “super-tasters” hired by the food and beverage industries. The other layer of personal, or even cultural, preferences adds nuances to how individuals operate with their unique sensory perspective of the world we all share. We understand this variation among our fellow humans. We may prefer different colors, we may love or hate cilantro or durian fruits, and we learn early on to try not to project our own subjective preferences onto others, nor to criticize theirs. And we try to help and accommodate individuals that, at birth or through misadventure, are compromised in any sensory abilities. Variation happens and human societies accommodates such. Yet, we seem to lose our perspective when we try to consider the sensory abilities of other species.

My favorite science writer, Ed Yong, recently reviewed an insightful new paper by John McGann in which he argues against the age-old idea that humans have a poor sense of smell compared to many other mammals. One of his primary lines of logic is that we have confused “different” with “better/worse” or, in other words, human sense of smell functions perfectly well, for humans, and we can detect specific smells or concentrations of such “better” than can some animals. More generally, McGann argues, neuroscientists and psychologists have for so long simply accepted the concept that humans have a poor sense of smell, that there are very few studies that have attempted to measure or test human smell.

On a different level, it is virtually impossible for humans, even scientists, to understand the sensory realms of animals that have fundamentally different sensory capacities. What does it feel (or “look” or “sound”) like to be able to sense the earth’s magnetic field, as can sea turtles and birds? How does a mouse appear in the composite image that a pitviper perceives in its visual cortex with the combined input from two “normal” eyes, plus the two infrared-capable eyes (the so-called pit organs)? We think that American crows are pure black, because that is what they look like to us, within our visible spectrum of color vision. Bird visual capabilities extend far into the ultraviolet realm, so it is highly unlikely that crows are simply pure black as far as all birds are concerned. The problem is that our minds cannot possibly imagine anything beyond what we can sense, and computer-generated images can only show us what we can sense. We live in a sensory world that is purely human. We have no concept how the world appears to these different creatures. But remember not to conflate “different” with “better/worse” because our sensory world suits us just fine, and I have yet to become bored with it.

See Ed Yong’s summary of smell here.

Publication: McGann, J. 2017. Poor human olfaction is a 19th-century myth. Science 356:
DOI: 10.1126/science.aam7263

Joe Mendelson, PhD
Director of Research