期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：6
页码：1892-1897
DOI：10.1073/pnas.1410844112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceSong-learning birds share several of the cognitive traits that underlie human speech. Continuous variation in swamp sparrow song notes, for example, is perceived in a categorical manner, similar to human perception of phonemes, the smallest units of human speech. Although speakers and listeners are generally unaware of the fact, many phonemic categories in speech vary in their structure and in how they are perceived, depending on linguistic context. Herein, we test how categorical perception in swamp sparrows is influenced by context and demonstrate that one note type is categorized differently, depending on its position within a song syllable. To our knowledge, our results suggest for the first time that this central characteristic of human phonology is also found in a nonhuman communication system. Some of the psychological abilities that underlie human speech are shared with other species. One hallmark of speech is that linguistic context affects both how speech sounds are categorized into phonemes, and how different versions of phonemes are produced. We here confirm earlier findings that swamp sparrows categorically perceive the notes that constitute their learned songs and then investigate how categorical boundaries differ according to context. We clustered notes according to their acoustic structure, and found statistical evidence for clustering into 10 population-wide note types. Examining how three related types were perceived, we found, in both discrimination and labeling tests, that an "intermediate" note type is categorized with a "short" type when it occurs at the beginning of a song syllable, but with a "long" type at the end of a syllable. In sum, three produced note-type clusters appear to be underlain by two perceived categories. Thus, in birdsong, as in human speech, categorical perception is context-dependent, and as is the case for human phonology, there is a complex relationship between underlying categorical representations and surface forms. Our results therefore suggest that complex phonology can evolve even in the absence of rich linguistic components, like syntax and semantics.
关键词：bird song ; categorical perception ; phonology ; speech perception
