20th century Philosophy saw a burgeoning interest in modalities of sensory perception un-enjoyed by humans. And the interest is well-deserved; for it is by looking to the physiognomy of bats and dogfish that we can best test our intuitions on whether or not adequate knowledge of an organism’s physical structure can ever tell us everything that we can know about what it is like to be that organism. However, philosophers tend to gravitate towards sonar and perceptual sensitivity to magnetic fields without paying attention to whether any lessons might be learned in less weird perceptual modes. Are non-human sensory modes like sonar always wholly unimaginable, or are some such modes more imaginable than others? If we can’t imagine what it is like to perceive through sonar, for instance, can we imagine what it is like to tell an object’s shape by our whiskers?
As the Economist reports, tremendous advances have recently been made in understanding how seals detect and perceive prey whilst swimming in murky water. When an object moves about under water, it creates a signature wake that carries information about the object. This information is lost on humans; a wake is a wake so far as our sensory systems are concerned. But a series of tests on a trained seal have shown that seals are able to discriminate objects whose width vary by as little as 2.8 cm, and can also distinguish objects of a similar width yet different shape.
This ability probably falls under the realm of good old-fashioned tactile perception, yet try as I might, I cannot imagine being able to distinguish the wake of a round object from that of a square one. At the same time, however, I feel inclined to contend that we can more easily imagine what it is like to have seal whiskers than what it is to perceive via sonar or disturbances in the magnetic field. Can seals help us to better understand the conceptual barriers that seem to arise in the more extreme cases of experience? Or might we even find that spending an afternoon in the pool after not shaving for a few months uncovers unknown sensory powers in our sideburns?