Perceptual classification based on the component structure of song in European starlings

The ability to recognize individuals based on their vocalizations is common among many species of songbirds. Examining the psychological and neural ba sis of this functionally relevant behavior can provide insight into the per ceptual processing of acoustically complex, real-world, communication signa ls. In one species of songbird, European starlings (Sturnus vulgaris), male s sing long and acoustically complex songs composed of small stereotyped no te clusters called motifs. Previous studies demonstrate that starlings are capable of individual vocal recognition, and suggest that vocal recognition results from the association of specific motifs with specific individuals. The present study tests this possibility by examining how variation among the motifs that comprise a song affect its discrimination and classificatio n. Starlings were trained, using operant techniques, to associate multiple songs from a single male starling with one response, and songs from four ot her male starlings with another response. The level of stimulus control exe rted by motif variation was then measured by having subjects classify three sets of novel song bouts in which motifs from the training songs were syst ematically recombined. The results demonstrate a significant, and approxima tely linear, relationship between song classification and the relative prop ortions of familiar motifs from different singers that compose a bout. The results also indicate that the motif proportion effects on song classificat ion are primary to retroactive interference in the recall for specific moti fs, and independent of any biases due to the syntactic organization of moti fs within a bout. Together, the results of this study suggest that starling s organize the complex vocalizations of conspecifics by memorizing large nu mbers of unique song components (i.e., motifs) that are then associated wit h different classes. Because individual starlings tend to possess unique mo tif repertoires, it is likely that under natural conditions such classes wi ll correspond to individual identity. Thus, it is likely that perceptual pr ocessing mechanisms similar to those described by the results of the presen t study form the basis for individual vocal recognition in starlings. (C) 2 000 Acoustical Society of America. [S0001-4966(00)04806-2].