Vocal tract constancy in birds and humans

Humans perceive speech as relatively stable despite acoustic variation caused by vocal tract (VT) differences between speakers. Humans use perceptual ‘vocal tract normalisation’ (VTN) and other processes to achieve this stability. Similarity in vocal apparatus/acoustics between birds and humans means that birds might also experience VT variation. This has the potential to impede bird communication. No known studies have explicitly examined this, but a number of studies show perceptual stability or ‘perceptual constancy’ in birds similar to that seen in humans when dealing with VT variation. This review explores similarities between birds and humans and concludes that birds show sufficient evidence of perceptual constancy to warrant further research in this area. Future work should 1) quantify the multiple sources of variation in bird vocalisations, including, but not limited to VT variations, 2) determine whether vocalisations are perniciously disrupted by any of these and 3) investigate how birds reduce variation to maintain perceptual constancy and perceptual efficiency.PostprintPeer reviewe

The multi-dimensional nature of vocal learning

Funding; S.C.V. was supported by a Max Planck Research Group (MPRG), a Human Frontiers Science Program (HFSP) Research grant (grant no. RGP0058/2016) and a UKRI Future Leaders Fellowship (grant no. MR/T021985/1). P.L.T. was supported by US Office of Naval Research (ONR) grant nos N00014-18-1-2062 and N00014-20-1-2709. B.P.K. was supported by the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 751356. V.C.B. was supported by the DK Cognition and Communication by the Austrian Science Fund (FWF) grant no. W1262-B29.How learning affects vocalizations is a key question in the study of animal communication and human language. Parallel efforts in birds and humans have taught us much about how vocal learning works on a behavioural and neurobiological level. Subsequent efforts have revealed a variety of cases among mammals in which experience also has a major influence on vocal repertoires. Janik and Slater (Anim. Behav.60, 1–11. (doi:10.1006/anbe.2000.1410)) introduced the distinction between vocal usage and production learning, providing a general framework to categorize how different types of learning influence vocalizations. This idea was built on by Petkov and Jarvis (Front. Evol. Neurosci.4, 12. (doi:10.3389/fnevo.2012.00012)) to emphasize a more continuous distribution between limited and more complex vocal production learners. Yet, with more studies providing empirical data, the limits of the initial frameworks become apparent. We build on these frameworks to refine the categorization of vocal learning in light of advances made since their publication and widespread agreement that vocal learning is not a binary trait. We propose a novel classification system, based on the definitions by Janik and Slater, that deconstructs vocal learning into key dimensions to aid in understanding the mechanisms involved in this complex behaviour. We consider how vocalizations can change without learning, and a usage learning framework that considers context specificity and timing. We identify dimensions of vocal production learning, including the copying of auditory models (convergence/divergence on model sounds, accuracy of copying), the degree of change (type and breadth of learning) and timing (when learning takes place, the length of time it takes and how long it is retained). We consider grey areas of classification and current mechanistic understanding of these behaviours. Our framework identifies research needs and will help to inform neurobiological and evolutionary studies endeavouring to uncover the multi-dimensional nature of vocal learning.Publisher PDFPeer reviewe

Morris water maze

No abstract available

Communication in Humans and Other Animals

Communication in Humans and Other Animals, Gisela Håkansson, Jennie Westander, John Benjamins, Amsterdam, PA (2013), Pp. xi + 242. Price €36.00 paperback, €99.00 hardback

Learning strategies and the social brain: missing elements in the link between developmental stress, song, and cognition?

Bird songs may advertise aspects of cognition because song learning and learning speed in cognitive tasks are both affected by early‐life environments. However, such relationships remain ambiguous in the literature. Here, I discuss 2 lines of research that may help to demystify links between song learning and cognition. First, learning strategies should be considered when assessing performance to ensure that individual differences in learning ability are not masked by individual differences in learning strategies. Second, song characteristics should be associated with social behavior because songs have a social purpose and, consequently, should be strongly related at functional and neural levels. Finally, if song learning and cognitive abilities are correlated because they develop concurrently and/or share or compete for the same resources, I discuss ways glucocorticoids may link early‐life stress, song learning and cognitive ability, focusing particularly on oxidative stress as a potential mechanism

Directional asymmetries in vowel perception of adult nonnative listeners do not change over time with language experience

Purpose: This study tested an assumption of the Natural Referent Vowel (Polka & Bohn, 2011) framework, namely, that directional asymmetries in adult vowel perception can be influenced by language experience. Method: Data from participants reported in Escudero and Williams (2014) were analyzed. Spanish participants categorized the Dutch vowels /aː/ and /ɑ/ in 2 separate sessions: before and after vowel distributional training. Sessions were 12 months apart. Categorization was assessed using the XAB task, where on each trial participants heard 3 sounds sequentially (first X, then A, then B) and had to decide whether X was more similar to A or B. Results: Before training, participants exhibited a directional asymmetry in line with the prediction of Natural Referent Vowel. Specifically, Spanish listeners performed worse when the vowel change from X to A was a change from peripheral to central vowel (/ɑ/ to /aː/). However, this asymmetry was maintained 12 months later, even though distributional training improved vowel categorization performance. Conclusions: Improvements in adult nonnative vowel categorization accuracy are not explained by attenuation of directional asymmetries. Directional asymmetries in vowel perception are altered during native language acquisition, but may possibly be impervious to nonnative language experiences in adulthood