Object representation in echolocating bats: Recognition of targets from different orientations

Abstract

Big brown bats (Eptesicus fuscus) can discriminate among objects using wideband FM sonar sounds. Bats could perceive and represent only the acoustic dimensions of echoes (e.g., delay, frequency, amplitude), or they could use those dimensions to reconstruct object features (e.g., distance, shape, size). To investigate this question, bats were presented with a two-alternative (left/right) forced-choice sonar discrimination task. The stimuli were a one-cylinder monopole target and a two-cylinder dipole target that was presented at all aspect angles. Acoustic dimensions of the dipole echoes change depending on aspect angle. If the bats represent only acoustic dimensions, they should have difficulty selecting the dipole. If the bats represent object features, they should be able to select the dipole independent of aspect angle. Bats can select the dipole over a wide range of aspect angles, suggesting that they construct object features from echo acoustic dimensions. The bats’ error patterns may indicate the echo dimensions they use to construct object features. [Work supported by NIH and ONR.]