Globally, human parents engage in a distinctive, melodic, high-pitched style of communication known as "baby talk" with their infants. This unique form of expression is believed to foster bonds and delineate the structure of language for babies. Interestingly, a recent study published in the Proceedings of the National Academy of Sciences suggests a similar behavior among bottlenose dolphins, a finding never before observed in nonhuman species.
Bottlenose dolphins, researchers found, modulate their vocalizations when interacting with their offspring. Such an adaptation could potentially promote connection and learning within the dolphin community. The study's outcome is predicted to stimulate further investigations in animal communication, according to dolphin specialist Janet Mann from Georgetown University. She suggests that these discoveries may also shed light on the evolution of vocal learning, which forms the basis of language.
Unique among bottlenose dolphins is the "signature whistle," analogous to human names. These creatures use their distinct high-pitched whistles to communicate with their peers, maintain contact, and signal urgency. Young dolphins adopt these characteristic sounds during their initial year, but the acquisition process remains a mystery. They also recognize and mimic the signature whistles of their mothers and other pod members.
The scientists of the Sarasota Dolphin Research Program in Florida had accumulated substantial data of dolphin vocalizations when they decided to investigate signs of "baby talk." They selected 19 female dolphins from their extensive database, recorded between 1984 and 2018, both in the presence and absence of their calves. Upon close examination of the recordings, the researchers discovered a distinct pattern. When in the presence of their offspring, all 19 dolphins vocalized at higher frequencies and displayed broader bandwidth in their whistles, a pattern similar to human "baby talk."
Lead author Laela Sayigh, a biologist at the Woods Hole Oceanographic Institution, does not believe these altered vocalizations are stress-related as previous studies have linked stress to increased whistle rates, which was not observed here.
There's evidence that human infants prefer "baby talk" over normal speech, whether the same applies to dolphin calves is yet to be determined. Regardless, these modified communication patterns seem to enhance social bonds and facilitate language learning in humans.
Sayigh suggests that dolphin mothers probably use "baby talk" to catch the attention of their calves, even though the calves have already developed their unique signature whistles by the age of 2. Elise Piazza, a brain and cognition scientist from the University of Rochester, concurs with this proposition, considering the dolphins' large, mobile communities, and the importance of constant communication.
The research findings could be influential in understanding the origins of language development in humans, says behavioral ecologist Karl Berg from the University of Texas Rio Grande Valley. This discovery, particularly in creatures as evolutionarily divergent as dolphins and humans, may shed light on the evolutionary underpinnings of vocal learning and language formation.
This discovery could inspire further research on "baby talk" in other species that learn vocally, such as parrots and seals. Berg adds, "Any vocal-learning species with significant social bonds between parent and offspring might show this." The quest for these discoveries continues.