Rules, rhythm and grouping : auditory pattern perception by birds

Both language and music are universal and characteristic for humans. The evolution of the cognitive abilities underlying language and music are widely debated. A core question is whether these abilities find their origins in a modification or extension of general cognitive abilities for processing auditory input also present in other species. If so, comparative studies of nonhuman animals should reveal similarities in processing abilities. In this paper, we review some examples of such studies. We focus on whether birds (in particular zebra finches, Taeniopygia guttata , and budgerigars, Melopsittacus undulates ) can detect structural patterns based on relational rather than on physical similarities among auditory stimuli – an essential ability for processing and producing language and music. We briefly discuss why birds are suitable model species. Next, we discuss three domains of pattern detection: the ability to (1) detect ‘grammatical rules’ underlying sound strings; (2) perceive regular rhythms and (3) spontaneously group separate sounds into a larger pattern. In all of these there is evidence that birds show some ability to detect relational patterns. However, there is also variation between species: while budgerigars show relational rule learning, zebra finches attend to local physical similarities between sound strings used for training and testing. For rhythm detection, zebra finches and budgerigars show no clear differences. However, a broader comparison indicates that here too differences are present in the extent to which different bird species attend to relational patterns or to local features. Finally, spontaneous grouping of sounds was shown in zebra finches. The clear variation among bird species in their perceptual and cognitive abilities, in combination with their accessibility for experimental studies, provides opportunities to study the variation in auditory processing mechanisms and how these evolved. This may also provide hypotheses for the evolution of these abilities in humans.