Acquiring a language is a difficult process. One of the best ways to learn involves the use of a tutor. This one-on-one interaction allows for direct learning as well as interaction without distraction. Usually, the teacher is an expert in that specific language. But when it comes to learning a first language, the most useful tutor happens to be an infant’s parent.
Babies actually begin to learn speech before birth as they gain perspective on phonetics. Afterwards, they rely on their parents to provide them with a variety of lessons to improve their ability to communicate. However, not all methods are effective and several parameters such as the frequency, amplitude, and timing of speech are critical in determining how well a child will attend to speech and, ultimately, learn speech sounds.
Researchers have attempted for years to understand why these particular aspects of language tutoring play such an important role though the answers have been difficult to ascertain. Yet we may now know why these acoustic modulations to speech are important for speech learning thanks to a team of researchers at McGill University led by Dr. Jon Sakata. They have published a study in the Proceedings of the National Academy of Sciences demonstrating how and why vocal learning is heavily influenced by personalized, face-to-face tutoring. They accomplished this not with humans, however, but with songbirds.
Though humans and an avian species may not appear to have much in common, in terms of vocal learning, they both share significant perceptual, cognitive, and social requirements . Researchers have even shown that a particular species, the zebra finch, shows remarkable similarities to humans in terms of the processes of vocal learning. Of particular importance is that in both zebra finches and humans, social interactions critically shape how individuals learn their vocalizations.
The experimental process performed by Sakata’s team was rather straightforward. Young finches around 6 weeks of age were placed into one of two situations. The first, known as social tutoring, involved placing the birds in a cage beside another cage containing an adult male finch (‘tutor’). The second was passive tutoring in a soundproof box such that exposure to songs occurred using a speaker.
The learning experience occurred over five days after which point the birds were housed individually for at least two months to allow their songs to develop. The authors found that the adult songs of socially tutored juveniles were significantly more similar to their tutors’ songs than those of passively tutored juveniles, indicated that socially tutored birds learned their tutors’ songs better. Additionally, they found a very close relationship between attention and song learning; juveniles that were more attentive to their tutors’ songs showed significantly better song learning.
There was another interesting outcome of this experiment. The tutors not only directed their songs towards juveniles but also, as might be expected, directed their songs away from the young birds. The students, in turn, seemed to discern between the two types. In particular, they paid more attention to the songs that were intended for them.
This result led the authors to investigate the degree to which the songs differed when tutors directed songs toward juveniles. They found introductory notes were produced more frequently during the directed songs; in some sense, tutors could have been doing their best to get the students to pay attention. In addition, the lesson sections, known as motifs, were spaced further apart, giving the younger birds an opportunity to process and learn. In human terms, this delay matches the slower speech adults use when teaching children.
The final observation was a change in the pitch of tutor zebra finches’ songs, which was lower when tutors sung to students. This was quite interesting as humans also tend to change the pitch of their speech when talking to children, albeit in the opposite direction. Despite the difference in direction, either change in pitch could help students maintain their attention to the adult’s vocalization.
With the observations of student-directed songs completed, the group wanted to find out if these changes were unique to tutoring. To find out, they conducted the same experiment with one difference. Instead of juveniles, adult females were the audience members. The results were fascinating. The males produced more introductory notes when singing to females, just like with the juveniles, and this could have served to increase female attention to the male. But when it came to those motifs, males did not space them out more when singing to females.
From a social context, the change in song patterns for pupils made sense yet the authors wanted to find out if this had any correlation at the neurobiological level. They once again performed the tutoring experiment but instead of five days, the birds were only tutored for a few hours. The team then examined the brains of these students in the hopes of seeing a difference in one particular cellular factor known as Early Growth Response Protein 1 (EGR-1) . The protein is involved in song control and learning in finches and could also be important in recognition memory in humans . For the authors, EGR-1 offered the perfect marker to follow the progress of education, particularly in the social context.
The team was particularly interested in neurons in parts of the brain that mediate attention since attention and learning were closely related. As such, they examined EGR-1 expression in neurons from the locus coeruleus, which is responsible for attention and the ventral tegmental area, which is involved in reward . As for the type of neurons expressing EGR-1, those in the locus coeruleus produce norepinephrine while those in the ventral tegmental area produce dopamine. Both of these neuron types are suspected to be involved in various forms of learning, including language learning, yet this has not been proven.
When the team completed their explorations, they were pleased with the results. As expected, juveniles with social tutoring had a significantly higher level of EGR-1 expression in these neurons compared to birds that were not tutored. But there was a surprise as passive tutoring did not lead to a rise in EGR-1 expression. From a purely molecular perspective, they appeared to have had no tutoring at all.
In terms of human learning, this study offers a reason behind the supremacy of social interaction in learning a language. By having a tutor who focuses on helping the individual student, the brain is activated in such a way that it may be able to acquire and retain more. Add in the reward factor from both teacher and dopamine and the seed for even further interest is planted. Although having a tutor may not guarantee success, this study suggests more can be accomplished with a tutor than simply relying on dictionaries, textbooks, and computer software.
Original Research Article:
Chen Y, Matheson LE, Sakata JT. Mechanisms underlying the social enhancement of vocal learning in songbirds. Proc Natl Acad Sci U S A. 2016 Jun 14;113(24):6641-6. doi: 10.1073/pnas.1522306113. Epub 2016 May 31.
