ITHACA, N.Y. -- Humans and other "higher" animals aren't so special when it comes to making life-or-death decisions in an instant, a Cornell University study of insect hearing has found. Even the lowly cricket employs a sophisticated capability, called categorical perception, when its life (or love life ) is at stake.
"Crickets -- and probably many other types of animals -- have found a simple way to build a system that responds quickly," said Robert A. Wyttenbach, the Cornell postgraduate associate of neurobiology and behavior who gave crickets a perception test originally developed for human infants. "Crickets have to make a yes-or-no decision in a hurry, and ones that waffle become bat bait."
For a cricket flying through the night air, life is a sound spectrum-filling cacophony, Wyttenbach said, but only two sound sources really matter: other crickets, calling at 4 to 5 kHz (4-5 kilohertz, the familiar chirping that is just above the highest note on the piano), and insect-eating bats, emitting ultrasound that helps echolocate their prey at 25 to 80 kHz (humans with good hearing can detect sounds up to 20 kHz).
Steering toward the low-frequency cricket sound might help the flier find a mate, or at least the company of other crickets. However, failing to steer away from bats' ultrasound could cost the cricket not only its life but its place in the gene pool, explained Ronald R. Hoy, the Cornell professor of neurobiology and behavior whose laboratory conducted the experiments. Researchers led by Hoy reported in 1978 that crickets can detect bats' ultrasound and take evasive action, but those flight studies never answered the question: What is the cut-off line between "good" sounds and "bad", and how does the insect decide?
The study is reported in the journal Science,(Sept. 13, 1996), in a report by Wyttenbach, Hoy and Michael L. May, a former Cornell graduate student, "Categorical Perception of Sound Frequency by Crickets."