Behavioural Processes 84 (2010) 421–427 Contents lists available at ScienceDirect Behavioural Processes journal homepage: www.elsevier.com/locate/behavproc Using network models of absolute pitch to compare frequency-range discriminations across avian species Ronald G. Weisman a,∗ , Marisa Hoeschele b , Laurie L. Bloomfield c , Douglas Mewhort a , Christopher B. Sturdy b a Queen’s University, Canada b University of Alberta, Canada c Algoma University, Canada article info Article history: Received 9 September 2009 Received in revised form 15 January 2010 Accepted 18 January 2010 Keywords: Absolute pitch Animals Birds Quantitative network model Frequency-range discrimination Song and call recognition abstract The spectral frequency ranges of song notes are important for recognition in avian species tested in the field. Frequency-range discriminations in both the field and laboratory require absolute pitch (AP). AP is the ability to perceive pitches without an external referent. The authors provided a network model designed to account for differences in AP among avian species and evaluated it against discriminative performance in eight-frequency-range laboratory tests of AP for five species of songbirds and two species of nonsongbirds. The model’s sensory component describes the neural substrate of avian auditory percep- tion, and its associative component handles learning of the discrimination. Using only two free parameters to describe the selectivity and the sensitivity of each species’ auditory sensory filters, the model provided highly accurate predictions of frequency-range discrimination in songbirds and in a parrot species, but performance and its prediction were less accurate in pigeons: the only species tested that does not learn its vocalizations. Here for the first time, the authors present a model that predicted individual species’ per- formance in frequency-range discriminations and predicted differences in discrimination among avian species with high accuracy. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Birds and mammals are rarely without a voice, and their vocalizations are of demonstrable importance in communication among members of the same species (termed conspecifics). Natu- ral selection has experimented with vocal communication learned by imitation in only a tiny number of distantly related orders and suborders of birds and mammals. Among birds, only true songbirds (oscines), humming birds (Apodiformes), and parrots (Psittaciformes) learn their vocalizations. Among mammals, only whales and dolphins (Cetaceans), bats (Chiroptera), elephants (Ele- phantidae loxdonta), and of course humans (Homo sapiens) learn their vocalizations. Comparisons in communication between vocal learning and nonlearning species, and comparisons among vocal learning species are the most powerful tools comparative scien- tists can apply to understand the evolution of communication (see Jarvis, 2006, for a review). In this article, we have focused on the perceptual basis of vocal communication in birds, and especially in ∗ Corresponding author at: Department of Psychology, Queen’s University, 99 Uni- versity Avenue, Kingston, Ontario, K7L3N6, Canada. Tel.: +1 613 540 4150; fax: +1 613 533 2499. E-mail address: ronald.weisman@queensu.ca (R.G. Weisman). oscines. The flexibility and subtlety of oscines’ learned songs and calls are important determinants of oscines’ success as a suborder. In fact, oscines are highly successful; they constitute roughly half of the approximately 9000 living species of birds. 1.1. Auditory perception in song playback experiments Bird songs are most commonly studied in playback experi- ments conducted in the field. In a playback study, territorial males hear songs either recorded from conspecifics or synthesized to resemble conspecifics’ songs. The quantification of vigorous male territorial responses (e.g., approaches to the loud speaker) mea- sures the potency of the perceptual features or characteristics of songs manipulated during playback experiments. Playback studies measure the biological importance of a song’s perceptual features directly in nature, without any laboratory artifice. There are hundreds of published studies of song playback in dozens of oscine species (see McGregor, 1992; Slater, 2003). From these field experiments, it is now well known that songbirds col- lect information about several perceptual features of songs (e.g., number of notes, note duration, and the harmonic structure of notes) in order to identify conspecifics (e.g., Nelson, 1988). In study- ing this vast literature, it became apparent to our research group 0376-6357/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.beproc.2010.01.010