Evidence for cumulative cultural evolution in bird song

In studies of cumulative cultural evolution in non-human animals, the focus is most often on incremental changes that increase the efficacy of an existing form of socially learned behaviour, such as the refinement of migratory pathways. In this paper, we compare the songs of different species to describe patterns of evolution in the acoustic structure of bird songs, and explore the question of what building blocks might underlie cumulative cultural evolution of bird song using a comparative approach. We suggest that three steps occurred: first, imitation of independent sounds, or notes, via social learning; second, the formation of categories of note types; and third, assembling note types into sequences with defined structures. Simple sequences can then be repeated to form simple songs or concatenated with other sequences to form segmented songs, increasing complexity. Variant forms of both the notes and the sequencing rules may then arise due to copy errors and innovation. Some variants may become established in the population because of learning biases or selection, increasing signal efficiency, or because of cultural drift. Cumulative cultural evolution of bird songs thus arises from cognitive processes such as vocal imitation, categorization during memorization and learning biases applied to basic acoustic building blocks. This article is part of a discussion meeting issue ‘The emergence of collective knowledge and cumulative culture in animals, humans and machines’.

Singers show enhanced performance and neural representation of vocal imitation

Humans have a remarkable capacity to finely control the muscles of the larynx, via distinct patterns of cortical topography and innervation that may underpin our sophisticated vocal capabilities compared with non-human primates. Here, we investigated the behavioural and neural correlates of laryngeal control, and their relationship to vocal expertise, using an imitation task that required adjustments of larynx musculature during speech. Highly trained human singers and non-singer control participants modulated voice pitch and vocal tract length (VTL) to mimic auditory speech targets, while undergoing real-time anatomical scans of the vocal tract and functional scans of brain activity. Multivariate analyses of speech acoustics, larynx movements and brain activation data were used to quantify vocal modulation behaviour and to search for neural representations of the two modulated vocal parameters during the preparation and execution of speech. We found that singers showed more accurate task-relevant modulations of speech pitch and VTL (i.e. larynx height, as measured with vocal tract MRI) during speech imitation; this was accompanied by stronger representation of VTL within a region of the right somatosensory cortex. Our findings suggest a common neural basis for enhanced vocal control in speech and song. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Endogenous and social factors influencing infant vocalizations as fitness signals

This dissertation evaluated the role of social and endogenous prelinguistic vocalizations as vocal fitness signals in human development. It consists of three studies. The first investigated the saliency of infant vocal imitation using listener judgments regarding the degree of imitativeness in parent-infant vocal turn pairs. Participating listeners demonstrated moderate to high intra- and inter-rater agreement, suggesting vocal imitation has the potential to be used as a signal of fitness to caregivers in early development. The work also showed that vocal imitation in infancy is rare. The second study sought to quantify the extent to which infants produce vocalizations socially (directed to a caregiver) vs endogenously (not directed to a caregiver) in laboratory settings where parents either attempted to engage them or talked with another adult. The infants produced three times as many vocalizations endogenously as socially in both settings. High rates of endogenously produced sounds may result from evolutionary pressures to signal wellness to caregivers through vocalization. Extensive independent vocal play may offer infants the opportunity to explore sensorimotor characteristics of the vocal system and provide the raw material that parents can use in face-to-face interactions. The third study examined social and endogenous motivations in the emergence of advanced vocal forms. Specifically, it compared canonical babbling ratios of infants at low- and high-risk for autism across high and low levels of both vocal turn-taking and vocal play. Both groups showed a tendency to produce more canonical babbling during high turn-taking and high vocal play. The findings highlight a potentially robust internal social motivation for vocalization, even in the presence of likely social-cognitive differences such as risk for autism. High rates of endogenously produced canonical syllables in high-risk infants support the idea of robust evolutionary pressures for infants to signal fitness through vocalization. Furthermore, differences in vocal production across settings can inform our understanding of the importance of both vocal interaction and independent infant exploration of vocalization. This dissertation offers perspective on the ways in which social and endogenous factors reveal natural selection pressures on fitness signaling in the human infant.

A memory-driven auditory program ensures selective and precise vocal imitation in zebra finches

In the vocal learning model, the juvenile first memorizes a model sound, and the imprinted memory gradually converts into vocal-motor output during the sensorimotor integration. However, early acquired memory may not precisely represent the fine structures of a model sound. How do juveniles ensure precise model imitation? Here we show that juvenile songbirds develop an auditory learning program by actively and attentively engaging with tutor’s singing during the sensorimotor phase. The listening/approaching behavior requires previously acquired model memory and the individual variability of approaching behavior correlates with the precision of tutor song imitation. Moreover, it is modulated by dopamine and associated with forebrain regions for sensory processing. Overall, precise vocal learning may involve two steps of auditory processing: a passive imprinting of model memory occurs during the early sensory period; the previously acquired memory then guides an active and selective engagement of the re-exposed model to fine tune model imitation.

Vocal Imitation and Linguistic Processing of Super Mario Theme Music by Yorùbá Gamers

An aspect of gaming culture among Yorùbá millennials is the linguistic interpretations of the background music that accompanies the popular video game called Super Mario. The themes of the interpretations are comparable to those of music texts at traditional Yorùbá events. Drawing on the Yorùbá tradition, the account is that the gamers assumed that the background music of the game has a similar function as the music at traditional Yorùbá events. The choice of words in the interpretation is conditioned by the situational contexts where the music is heard in the video game. The results of acoustic analyses show that the interpretations are also determined by mapping the pitch trajectories of the music melodies to the tones of the gamers’ language. Notably, the results of this study suggest that the linguistic processing of music may not only involve phonetic iconicity (Steinbeis and Koelsch, 2011) but situational context and social expectation.

The Effects of a Multimodal Music Program on Young Children’s Facial Expressions During Controlled Singing Tasks

Understanding children’s emotional perceptions of creative tasks can contribute to the optimal design of music programs. Little is known of how young children perceive vocal tasks, and whether music training changes their emotional perceptions. This research examined children’s facial expressions while performing vocal imitation and improvisation tasks before and after music training. Young children ( N=79) aged four to six years were randomly assigned to a multimodal music program, Lego training, or a no-treatment control group. Their facial expressions while performing the tasks were analyzed, and learning outcomes were assessed by measuring participants’ pitch accuracy and improvisation skills at pre-and post-training. The results yielded no significant differences among the groups’ facial expressions. There was, however, a significant main effect of time such that participants showed more Surprise while performing vocal improvisation tasks. While participants in the multimodal music program scored higher on measures of pitch accuracy and improvisation skill, it may be necessary to increase the duration of early childhood music programs to reduce their feelings of apprehension when performing vocal improvisation tasks.

Singers and non-singers differ in the performance and neural representation of vocal imitation

Humans have a remarkable capacity to finely control the muscles of the larynx, via distinct patterns of cortical topography and innervation that may underpin our sophisticated vocal capabilities compared with non-human primates. Here, we investigated the behavioural and neural correlates of laryngeal control, and their relationship to vocal expertise, using an imitation task that required adjustments of larynx musculature during speech. Highly-trained human singers and non-singer control participants modulated voice pitch and vocal tract length (VTL) to mimic auditory speech targets, while undergoing real-time anatomical scans of the vocal tract and functional scans of brain activity. Multivariate analyses of speech acoustics, larynx movements and brain activation data were used to quantify vocal modulation behaviour, and to search for neural representations of the two modulated vocal parameters during the preparation and execution of speech. We found that singers showed more accurate task-relevant modulations of speech pitch and VTL (i.e. larynx height, as measured with vocal tract MRI) during speech imitation; this was accompanied by stronger representation of VTL within a region of right dorsal somatosensory cortex. Our findings suggest a common neural basis for enhanced vocal control in speech and song.

Song imitation in congenital amusia: Performance partially facilitated by melody familiarity but not by phonetic content

Congenital amusia is a neurogenetic disorder of pitch perception that may also compromise pitch production. We explored whether vocal imitation of song in amusia is influenced by melody familiarity and phonetic content. Thirteen Mandarin-speaking amusics and 13 matched controls imitated novel song segments with lyrics and on the syllable /la/ while their output was recorded. Eleven out of these participants in each group also imitated segments of a familiar song. Subsequent acoustic analysis was conducted to measure pitch and timing matching accuracy. While amusics’ performance was facilitated by melody familiarity in terms of pitch interval deviation, signed interval deviation and number of contour errors, they showed compromised performance compared to controls in absolute pitch deviation, number of pitch interval errors, duration difference, interonset interval difference, and number of time errors in both familiar and novel song conditions. The presence of lyrics did not affect either group’s performance substantially. While a stronger relationship between music perception and novel melody imitation was observed in amusics as opposed to familiar melody imitation, controls showed the opposite pattern. We discuss the implications of the study in terms of music familiarity, memory demands, the relevance of lexical information and the link between perception and production.

Spoken Vocabulary Outcomes of Toddlers With Developmental Delay After Parent-Implemented Augmented Language Intervention

Purpose Early intervention using augmentative and alternative communication (AAC) supports both receptive and expressive language skills. However, many parents and clinicians still worry that augmented language intervention might delay or impair speech development. This study aimed to (a) characterize and analyze the speech sound development of toddlers with developmental delay who participated in a parent-implemented language intervention; (b) examine the accuracy of speech sounds among toddlers who participated in an augmented language intervention using speech-generating devices and toddlers who participated in a traditional, spoken language intervention; and (c) examine the relationship between baseline factors (i.e., receptive and expressive language skills, vocal imitation, and number of unintelligible utterances) and the number of spoken target vocabulary words after intervention. Method This study used extant data from two randomized control trials of parent-implemented language interventions using AAC or spoken language. Out of 109 children who completed the intervention, 45 children produced spoken target vocabulary words at the end of the intervention. We identified and phonetically transcribed spoken target vocabulary words for each child and then classified them based on Shriberg and Kwiatkowski's (1982) developmental sound classes. Results Children's speech sound accuracy was not significantly different across intervention groups. Overall, children who produced more words had more speech sound errors and higher baseline language scores. Intervention group and baseline receptive and expressive language skills significantly predicted the number of spoken target vocabulary words produced at the end of intervention. Conclusions Participation in AAC intervention resulted in significantly more spoken target vocabulary words and no statistically significant differences in speech sound errors when compared to children who received spoken language intervention without AAC. Results support using AAC interventions for very young children without the fear that it will delay speech or spoken language development. Supplemental Material https://doi.org/10.23641/asha.14265365