High plasticity in marmoset monkey vocal development from infancy to adulthood

Abstract

The vocal behavior of human infants undergoes marked changes across their first year while becoming increasingly speech-like. Conversely, vocal development in nonhuman primates has been assumed to be largely predetermined and completed within the first postnatal months. Contradicting this assumption, we found a dichotomy between the development of call features and vocal sequences in marmoset monkeys, suggestive of a role for experience. While changes in call features were related to physical maturation, sequences of and transitions between calls remained flexible until adulthood. As in humans, marmoset vocal behavior developed in stages correlated with motor and social development stages. These findings are evidence for a prolonged phase of plasticity during marmoset vocal development, a crucial primate evolutionary preadaptation for the emergence of vocal learning and speech.

Complex rules of vocal sequencing in marmoset monkeys

“…Calls containing more than 4 syllables were rare (~0.4%, Figure 2B), thus were not included in the following analyses. Consistent with the Zipf's law that was used to describe the complexity of vocal sequence [20][21][22][23], the proportion of occurrence for different ranks of N-phee calls showed a linear relationship in log-log plot, with a Zipf value of -1.86 (Figure 2C). Through chunking of original phee syllable sequences, we obtained new phee call sequences, as shown by representative data from three marmosets in Figure 2D (See Figure S1 for data from all 110 marmosets).…”

A convergent interaction engine: vocal communication among marmoset monkeys

“…B 377: 20210098 showed a delay in the development of the adult vocal repertoire [124]. They also produced noisier (less mature) calls, differed in the usage of calls, and did not show some typical call combinations [125,126].…”

“…Offspring separated from their parents, which thus received limited vocal feedback, produced infant-specific calls for longer and showed a delay in the development of the adult vocal repertoire [124]. They also produced noisier (less mature) calls, differed in the usage of calls, and did not show some typical call combinations [125,126].…”

Arousal elevation drives the development of oscillatory vocal output

“…Derivation of period We estimate the angular frequency 𝜔 𝑐 near the bifurcation as 𝜇 → 0 + . To further simplify the problem, as the delay is dominated by the energy delay 𝛿 𝑎 and 𝜔𝛿 𝑣𝑠 ≪ 1, equations ( 8) and (9)…”

“…Early vocalizations are driven by internal needs and act as scaffolding for later, more adaptive communicative functions [1]. In the infants of humans [3,4], songbirds [5,6], bats [7], and marmoset monkeys [8][9][10], vocalizations transition through different states on their way to becoming adult-like. While it is natural to presume that a behavioral state change must be the result of a neural change, the fact of the matter is that the development of vocal behavior involves multiple components, including the biomechanics of the vocal apparatus, the metabolic energy, neural systems, and the social environment [11].…”