The electric landscape

In his remarkable TED Talk "Can We Create New Senses for Humans?," neuroscientist David Eagleman describes the concept of the umwelt -- the part of the available stimulus space sampled by a particular animal's senses.  A simple example is the thin slice of the electromagnetic spectrum our eyes are sensitive to -- the familiar ROYGBIV of the rainbow.  There's plenty of electromagnetic radiation outside of that slice; gamma rays, x-rays, ultraviolet light, infrared light, microwaves, and radio waves are all ordinary photons, just like visible light is.  It's just that our eyes aren't sensitive to those frequencies, so they're outside of our umwelt.

The umwelt also has to do with the relative weighting of senses; how big a part of our sensory world a particular experience constitutes.  Most humans have a sense of smell, but my dogs live in a far richer olfactory world than I do.  But even how those inputs are utilized -- i.e., what kind of information they provide for making sense of the world -- can vary greatly.  Bats and dolphins use hearing in much the same way as we use our eyes, creating "sonic landscapes" of the objects around them.  What's kind of amazing, though -- and one of the main points of Eagleman's talk -- is that humans can train their brains to use other "peripherals" (as he calls them) to learn about the world, such as blind people who have learned to navigate the space around them by making clicking noises and listening for echoes from nearby obstacles.

It's always been fascinating to me to consider how the world would look to a night-flying echolocating bat.  Do they "see" their world through their ears and auditory cortex?

The topic of how other animals perceive their worlds -- and how different it could be from what we experience -- comes up because of a paper this week in the journal Nature about how elephantnose fish (Gnathonemus petersii), which live in murky streams in west and central Africa where eyesight doesn't serve much purpose, develop their visual picture of the world (including locating prey) using electric fields.  And not only do they gain information by creating and sensing electrical signals, they enhance those pictures using the signals created by nearby members of their species, making them one of the only known animals that relies on collective signal production and sensing.

Gnathonemus petersii [Image is in the Public Domain]

"Think of these external signals as electric images of the objects that nearby electric fish automatically produce and beam to nearby fish at the speed of light," said Federico Pedraja of Columbia University, who headed the study. "Our work suggests that three fish in a group would each receive three different "electrical views" of the same scene at virtually the same time."

The elephantnose fish's capacity for working in groups is a little like humans out on a search at night with flashlights.  One person with one flashlight would have a small illuminated field of view, but if there were twenty people it would go much faster, not only because of greater manpower, but because each person wouldn't be restricted to what is revealed by only their own flashlight beam.  Just as with twenty different flashlights in the night rather than a single one, in the case of elephantnose fish, the electrical fields produced by their neighbors clarify the picture they all receive.

"In engineering it is common that groups of emitters and receivers work together to improve sensing, for example in sonar and radar," said Nathaniel Sawtell, who co-authored the study.  "We showed that something similar may be happening in groups of fish that sense their environment using electrical pulses.  These fish seem to 'see' much better in small groups...  [They] have some of the biggest brain-to-body mass ratios of any animal on the planet.  Perhaps these enormous brains are needed for rapid and highly sophisticated social sensing and collective behavior."

To return to my original point -- how would the world look to an elephantnose fish?  Surely nothing like what we see.  Some sort of topography of electrical field strength, perhaps, creating an image of the obstacles they have to maneuver around, the prey they seek, and the predators they need to avoid.  But really, there's no way to know.  We're all trapped within our own umwelt.  I can't even imagine what the world is like for my dogs, who are a great deal more similar to me than these fish are.

To perceive the world like another living being does, you'd not only have to come equipped with their sensory systems, but put the information together using their brains.  We can only speculate, with all the inevitable biases that come from being locked in our own ways of knowing.  But this study did at least give us a hint of how different the world could appear -- if we were odd little fish living in muddy African rivers.

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