The abstract to the article starts like this:
Animals must encode fundamental physical relationships in their brains.
This seems rather implausible. But the examples they give for saying this seems plausible:
A heron plunging its head underwater to skewer a fish must correct for light refraction, an archerfish shooting down an insect must “consider” gravity, and an echolocating bat that is attacking prey must account for the speed of sound in order to assess its distance.
In these examples, refraction, gravity and the speed of sound affect the feedback connection between action and controlled variable. Assuming that the heron is controlling the optical angle to the fish, this angle will change as soon as the heron’s eye enters the water. But it can still control the angle despite this sudden change to the feedback function. So I think you could model this without giving the model the laws of refraction. The archerfish probably also controls the optical angle to its target but the connection from output to input is ballistic and its trajectory is affected by gravity. Thus the angle and distance to the target will affect the course of the output to the target. My guess is that the archerfish always tries to release it’s “arrow” when the insect is at a particular angle and distance with respect to the archerfish.
The effect of changing speed of sound does present an interesting problem if one assumes that the timing of the echo return is used as an absolute measure of distance from the reflecting surface. Since the speed of sound changes fairly substantially with temperature (and to some extent with altitude) it seems that timing cannot be a very accurate measure of absolute distance unless bats come equipped with a table of sound speed as a function of temperature and altitude. But for some reason, the authors conclude that bats come equipped with an innate knowledge of the speed of sound (I presume at some standard temperature and altitude). I have no idea how they come to this conclusion. But here’s what they say:
We addressed this question by shifting the speed of sound and assessing the sensory behavior of a bat species that naturally experiences different speeds of sound. We found that both newborn pups and adults are unable to adjust to this shift, suggesting that the speed of sound is innately encoded in the bat brain.
I would like to know what they mean by assessing the the sensory behavior that results from a shift in the speed of sound? Since they say that the research was conducted on “a species of bat that naturally experiences different speeds of sound” it seems like variations in the speed of sound are not a problem for these bats in terms of navigating around in the dark. So I don’t know what they mean by the finding that " both newborn pups and adults are unable to adjust to [the speed of sound shift that they created]". Very puzzling.
It would be nice if someone could get a copy of this paper to see what they did and what they found that led them to conclude that “the speed of sound is innately encoded in the bat brain”.