Songbirds as objective listeners: Zebra finches (Taeniopygia guttata) can discriminate infant-directed song and speech in two languages

Despite their acoustic similarities, human infants are able to discriminate between infant-directed song (as produced by human adults) and infant-directed speech in both English and Russian. However, experimenters are somewhat limited in what they can test using the preference paradigm with infants. As a complement to a previous infant study (Tsang et al. 2016), we asked whether a songbird, the zebra finch, could discriminate infant directed song and speech in English and Russian, and tested responses to stimuli that humans could not categorize as either type. Male and female zebra finches learned to discriminate the stimuli in both languages equally well, although females were slightly faster at learning the discrimination, and generalized responses to untrained stimuli of the same categories. Bird responses to stimuli that humans could not categorize likewise did not follow a clear pattern. Our results show that infant-directed song and speech are discriminable as categories by non-humans, that song and speech are as easy to discriminate in English and Russian, and that comparative studies together can provide more complete answers to research questions about auditory perception and acoustic features used for discrimination than using one species or one language alone.