Cricket direction discrimination --- a closer look
Crickets don't hear in the sense we do. When the female 'hears', she
does not experience separate perception of the two signals that reach right and
left ears. Instead, the two signals interact at very low levels to
generate a signal that corresponds to what might correspond to hearing.
Part of the interaction already takes place at the level of the eardrums:
Internal connections between the left and right eardrum cause differences in
amplitudes between the ears because external sounds get partially cancelled (or
amplified) by interference with internally (slower) transmitted sounds.
Sounds coming from the right of her position, for example, reach her right ear
slightly before reaching the left ear. The time delays correspond to the
direction of the chirping male and female crickets are very sensitive to these
delays.
(Emailed by zoologist
Martin Lankheet
of Wageningen UniversityMarch 4, 2010)
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