I have said that the essence of the belief
that bats have experience is that there is
something that it is like to be a bat. Now
we know that most bats (the microchiroptera,
to be precise) perceive the external world
primarily by sonar, or echolocation, detecting
the reflections, from objects within range,
of their own rapid, subtly modulated, high-frequency
shrieks. Their brains are designed to correlate
the outgoing impulses with the subsequent
echoes, and the information thus acquired
enables bats to make precise discriminations
of distance, size, shape, motion, and texture
comparable to those we make by vision. But
bat sonar, though clearly a form of perception,
is not similar in its operation to any sense
that we possess, and there is no reason to
suppose that it is subjectively like anything
we can experience or imagine. This appears
to create difficulties for the notion of
what it is like to be a bat. We must consider
whether any method will permit us to extrapolate
to the inner life of the bat from our own
case, 5 and if not, what alternative methods
there may be for understanding the notion.