Classification of biosonar target echoes based on coarse and fine spectral features in the bottlenose dolphin...

Previous bottlenose dolphin studies suggest that the coarse envelope of an echo spectrum ("macrostructure") has hierarchical dominance over finer-scale spectral features ("microstructure") during synthetic echo discrimination tasks. In this study, two dolphins listened to and discriminated between underwater sound stimuli consisting of pairs of clicks with different micro- and macrostructures. After conditioning dolphins to reliably discriminate between two "anchor" stimuli with different micro- and macrostructures, probe stimuli, which contained a macrostructure identical to one of the anchor stimuli and the microstructure of the alternate anchor, were infrequently presented. Dolphins responded to probes in a manner consistent with macrostructure primacy.