Young marmosets need their parents' direct feedback in order to evolve and stop making infant noises. According to new research developed by neuroscientists from Tübingen, baby monkeys who don't receive feedback from their parents develop innate vocalizations specific to adults, but are mixed with infant vocalizations.
The research group from Dr. Steffen Hage at the Tübingen Werner Reichardt Centre for Integrative Neuroscience (CIN) investigated the vocal motor production in correlation with the cognitive mechanisms that take place inside the monkeys' brains. The team conducted experiments with marmoset monkeys, which were ideal for a linguistic analysis, as they have a complex communication system.
Feedback From Parents Essential In Marmoset Monkeys' Communication
A marmoset family that was part of the study had three infants, and rejected one of them. It is a common practice among these animals to reject the third child, as they usually give birth to twins, and the parents often cannot handle a third child. The rejected baby was given to an animal caretaker at the CIN. But the researchers knew that these animals need their social groups, as they are used to living in stable social formations.
Consequently, the scientists wanted to bring the three siblings together as fast as possible, which happened after three months of separation, extremely soon for these animals' standards. The siblings have become adults by then and were raised as a stable group, displaying normal social behavior.
However, weeks after the reunion, the siblings still made baby noises, called "babbling" by the scientists. Generally, this type of language is displayed only throughout the first months of life of young monkeys. The researchers assumed that the siblings will let go of the babbling once they matured, but even as fully grown specimens they still retained it. The animals did acquire the adult linguistic capacities, but the two types of communication were mixed together.
"Using quantitative measures to compare call parameters and vocal sequence structure we show that, in contrast to normally raised marmosets, marmosets that were separated from parents after the third postnatal month still produced infant-specific vocal behaviour at subadult stages. These findings suggest a significant role of social feedback on primate vocal development until the subadult stages and further show that marmoset monkeys are a compelling model system for early human vocal development," noted the research.
The impact on this research lies in the importance of feedback in acquiring language structure and reaching language maturation. In the present research, the scientists started from the premise that the linguistic capacities of these animals are innate, only to discover that it is, in fact, a type of acquired behavior.
Communication Through Articulate Language An Acquired Skill
The research does bring insight on how neurolinguists perceive communication and language learning through different stages of maturation. Imitation has an important role in the way children learn to communicate and articulate sounds, especially in their first year of life, and the results of this study strongly suggest that feedback from parents is essential in acquiring linguistic skills.
"[...] It seems that developing the repertoire available to them heavily depends on direct feedback mechanisms much like our own. These animals are a compelling model system to investigate such early vocal development in humans. We can therefore learn a lot about early vocal development in humans from these animals," noted the team.
