Songbirds as vocal learners learn their songs and song preference from social tutors. Tutor choice for both song and preference learning are important to characterize for understanding individual... Show moreSongbirds as vocal learners learn their songs and song preference from social tutors. Tutor choice for both song and preference learning are important to characterize for understanding individual learning performance and cultural transmission of song. It is unclear whether early learned song preferences are generalised to songs similar to the tutor song and how simple versus complex early social environment might affect tutor choice and learning contents. This thesis addresses these questions in the zebra finch, the primary avian model for vocal learning studies, by reviewing the existing literature on song and preference learning and conducting three experiments. In these experiments, family raised female zebra finches were tested with a stimulus set of four songs along a gradient of decreasing similarity with the song they learned early in life. A breeding and song learning experiment comparing zebra finches raised with a single versus multiple tutors was conducted. The results suggest that female zebra finches generalise their early learned preferences for a specific song to other unfamiliar songs along a gradient of similarity. Social environment and individual differences can affect tutor choice for both song and preference learning in this colonial species. Show less
Humans and songbirds learn their vocalizations early in life by exposure to the vocalizations of adult conspecifics. Often, better learning outcomes are achieved with live, social, tutors than with... Show moreHumans and songbirds learn their vocalizations early in life by exposure to the vocalizations of adult conspecifics. Often, better learning outcomes are achieved with live, social, tutors than with audio-only exposure to vocalizations. Many researchers argue that this is because social tutor-tutee interactions are important in the vocal learning process. It is unclear, however, whether and to what extent live tutoring also facilitates song learning because it results in multimodal exposure to a tutor, as tutees can both see and hear their tutor, while audio-only tutoring results in unimodal exposure. This thesis investigates whether multi- compared to unimodal exposure affects song learning in zebra finches, the primary experimental animal model for vocal learning studies, by revisiting the zebra finch song learning literature and describing three song tutoring experiments. In these experiments, young birds were provided with audio-only or audio-visual tutor exposure, using one-way mirrors, videos and robotic birds. The results suggest that multi- versus unimodal exposure to a live tutor can affect the timing of vocal development and possibly the amount of vocal learning. Multimodal exposure to artificial tutors made stimulus presentation more salient but did not affect the song learning outcomes assessed in this thesis. Show less
Animal models, songbirds particularly, are increasingly used to study the human capacity for speech and language. In the light of understanding both language evolution and individual language... Show moreAnimal models, songbirds particularly, are increasingly used to study the human capacity for speech and language. In the light of understanding both language evolution and individual language acquisition these models are highly valuable, provided that they are studied within a valid comparative framework. In the past few decades, non-invasive methods such as functional Magnetic Resonance Imaging (fMRI) and Near-InfraRed Spectroscopy (NIRS) have become available for human as well as animal brain research. In the studies discussed in this thesis, fMRI is employed to unravel the neural correlates of vocal learning in the human and songbird brain. Specifically, fMRI in both songbirds and humans is used to study the neural mechanisms underlying birdsong learning and human artificial grammar learning. In a series of fMRI studies investigating these neural mechanisms in adult and juvenile zebra finches and human adults, this thesis compares the neural substrates of song learning in birds with those of language learning in humans. Studies in both species show correlations between behavioral learning of song or speech and neural activity. These results contribute to the songbird model for human vocal learning. Show less
This thesis provides a comparison of mostly perceptual development during vocal learning in songbirds (zebra finches) and human infants. The aim is to disentangle experience dependent and... Show moreThis thesis provides a comparison of mostly perceptual development during vocal learning in songbirds (zebra finches) and human infants. The aim is to disentangle experience dependent and independent processes during vocal learning. In both human infants and juvenile songbirds, a perceptual preference for __universal__ sounds was found, independent of adult auditory input. Later in development, both infants and juvenile songbirds show a change is preference. The juvenile songbirds clearly change their preference towards sounds they have been auditorily exposed to (chapter 3). In human infants in the influence of experience is less clear in this thesis. In combination with previous literature the most likely scenario is a combination of experience dependent and independent processes (chapter 2). To further compare human and birdsong phonology, a __typology__ of zebra finch song elements was performed (chapter 4). The results of this study indicate commonality as well as variation between populations in terms of phonology. In the order of elements within a sequence however, there is little evidence for common patterns across populations and there is variation within and between populations. In summary, this thesis shows similarities in developmental mechanisms in two vocally learning species. There might be a link between development and typology. Show less
Birdsong and human speech are both complex behaviours which show striking similarities mainly thought to be present in the area of development and learning. The most important parameters in human... Show moreBirdsong and human speech are both complex behaviours which show striking similarities mainly thought to be present in the area of development and learning. The most important parameters in human speech are vocal tract resonances, called formants. Different formant patterns characterize different vowels and are produced by moving articulators such as tongue and lips. However, not much is known about the production and perception of vocal tract resonances by birds. In this thesis I show that both songbirds and parrots use different articulators, comparable to humans, to modify the sound produced. While in songbirds beak gape and the expansion of the oropharyngeal-esophageal cavity are the most important articulators, parrots exhibit prominent tongue movements which also might explain their sophisticated ability to mimic human speech. Regarding formant perception I show that zebra finches can discriminate human words differing only in their vowels and categorize these words independent of speaker identity. To do so the birds employ, just like humans, a combination of intrinsic and extrinsic speaker normalization. Furthermore, when tested for a cue weighting bias both zebra finches and Dutch adults weight higher frequencies stronger. These results indicate that the mechanisms underlying vocal production and perception in birds and humans exhibit more similarities than realized before and studying birdsong will increase our knowledge about the emergence of these mechanisms and might even shed light on the evolution of human speech. Show less
