Tag: Slate

Antiphonal singing in indris

Selected coverage: Christian Science Monitor, Der Spiegel, National Geographic, Slate, Sciences et Avenir

“How to get noticed as a singer?” isn’t only a concern for young people aspiring to a career in the music industry. Young indris, critically endangered lemurs from Madagascar, sing in antiphony with their choirmates to increase their chances of getting noticed by rival groups, according to a new study in Frontiers in Neuroscience.

Indris (Indri indri) are one of the few species of primates that sing. They live only in the eastern rainforests of Madagascar, a habitat threatened by illegal logging. They live in small groups, which generally consist of a dominant female and male, their immature offspring, and one or more low-ranking young adults. Both females and males sing, and their songs play an important role in territorial defense and group formation.

In the new study, researchers from Italy, Germany, and Madagascar recorded 496 indri songs and analyzed their timing, rhythm, and pitch. The research is part of a long-term study on the ecology of indris in the vicinity of Andasibe-Mantadia National Park and the Maromizaha Forest, eastern Madagascar.

Group members carefully coordinate their singing, show the researchers. As soon as one indri starts to sing, all group members over two years typically old join in. Indris also tend to copy each other’s rhythm, synchronizing their notes.

“The chorus songs of the indri start with roars that probably serve as attention-getter for the other singers and continue with modulated notes of that are often grouped into phrases. In these phrases the indris give a high-frequency note at the beginning, and then the following ones descend gradually in frequency,” says Marco Gamba, a Senior Researcher at the Department of Life Sciences and Systems Biology of the University of Turin, Italy

“Synchronized singing produces louder songs, and this may help to defend the group’s territory from rival groups. Singing is interpreted as a kind of investment, which may help to provide conspecifics with information on the strength of the pair bond and the presence of potential partners,” says doctoral student Giovanna Bonadonna, who is one of the co-authors.

There is one exception to this pattern, however: young, lower-ranking individuals have a strong preference for singing in antiphony rather than synchrony with the rest of the chorus, alternating their notes with those sung by the dominant pair. Gamba and colleagues propose that this is a tactic that lets low-ranking indris maximize their solitary singing and emphasize their individual contribution to the song.

“Synchronized singing doesn’t allow a singer to advertise his or her individuality, so it makes sense that young, low-ranking indris sing in antiphony. This lets them advertise their fighting ability to members of other groups and signal their individuality to potential sexual partners,” says Bonadonna.

“Indris are indeed good candidates for further investigations into the evolution of vocal communication. The next steps in our studies will be to understand whether the acoustic structure of the units allows individual recognition and whether genetics plays a role in the singing structure,” says Professor Cristina Giacoma from the Department of Life Sciences and Systems Biology, the study’s final author.

 

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2016-06/f-asi060716.php

Study: http://journal.frontiersin.org/article/10.3389/fnins.2016.00249/full

 

How similar are the gestures of apes and human infants? More than you might suspect

Selected coverage: Smithsonian Magazine, Der Spiegel, LA Times, Slate, NBC, Discovery News, Yahoo, The Telegraph, Daily Mail

With Gozde Zorlu (Frontiers); Stuart Wolpert, Kristen Gillespie & Patricia Greenfield (UCLA Media Relations) 

Psychologists who analyzed video of a female chimpanzee, a female bonobo and a female human infant in a study to compare different types of gestures at comparable stages of communicative development found remarkable similarities among the three species.

This is the first time such data have been used to compare the development of gestures across species. The chimpanzee and bonobo, formerly called the “pygmy chimpanzee,” are the two species most closely related to humans in the evolutionary tree.

“The similarity in the form and function of the gestures in a human infant, a baby chimpanzee and a baby bonobo was remarkable,” said Patricia Greenfield, a distinguished professor of psychology at UCLA and co-author of the study.

Gestures made by all three species included reaching, pointing with fingers or the head, and raising the arms to ask to be picked up. The researchers called “striking” the finding that the gestures of all three species were “predominantly communicative,” Greenfield said.

To be classified as communicative, a gesture had to include eye contact with the conversational partner, be accompanied by vocalization (non-speech sounds) or include a visible behavioral effort to elicit a response. The same standard was used for all three species. For all three, gestures were usually accompanied by one or more behavioral signs of an intention to communicate.

Charles Darwin showed in his 1872 book “The Expression of the Emotions in Man and Animals” that the same facial expressions and basic gestures occur in human populations worldwide, implying that these traits are innate. Greenfield and her colleagues have taken Darwin’s conclusions a step further, providing new evidence that the origins of language can be found in gestures and new insights into the co-evolution of gestures and speech.

The findings are published today in the open-access journal Frontiers in Psychology.

The apes included in the study were named Panpanzee, a female chimpanzee (Pan troglodytes), and Panbanisha, a female bonobo (Pan paniscus). They were raised together at the Language Research Center in Atlanta, which is co-directed by Sue Savage-Rumbaugh, a co-author of the study. There, the apes learned to communicate with caregivers using gestures, vocalizations and visual symbols (mainly geometric shapes) called lexigrams.

“Lexigrams were learned, as human language is, during meaningful social interactions, not from behavioral training,” said the study’s lead author, Kristen Gillespie-Lynch, an assistant professor of psychology at the City University of New York and a former UCLA graduate student in Greenfield’s laboratory.

The human girl grew up in her parents’ home, along with her older brother. Where the apes’ symbols were visual, the girl’s symbols took the form of spoken words. Video analysis for her began at 11 months of age and continued until she was 18 months old; video analysis for the two apes began at 12 months of age and continued until they were 26 months old. An hour of video was analyzed each month for the girl, the chimpanzee and the bonobo.

Overall, the findings support the “gestures first” theory of the evolution of language. During the first half of the study, communicating with gestures was dominant in all three species. During the second half, all three species increased their symbol production — words for the child and lexigrams for the apes.

“Gesture appeared to help all three species develop symbolic skills when they were raised in environments rich in language and communication,” said Gillespie-Lynch, who conducted the research while she was at UCLA. This pattern, she said, suggests that gesture plays a role in the evolution, as well as the development, of language.

At the beginning stage of communication development, gesture was the primary mode of communication for human infant, baby chimpanzee and baby bonobo. The child progressed much more rapidly in the development of symbols. Words began to dominate her communication in the second half of the study, while the two apes continued to rely predominantly on gesture.

“This was the first indication of a distinctive human pathway to language,” Greenfield said.

All three species increased their use of symbols, as opposed to gestures, as they grew older, but this change was far more pronounced for the human child. The child’s transition from gesture to symbol could be a developmental model of the evolutionary pathway to human language and thus evidence for the “gestural origins of human language,” Greenfield said.

While gesture may be the first step in language evolution, the psychologists also found evidence that the evolutionary pathway from gesture to human language included the “co-evolution of gestural and vocal communication.” Most of the child’s gestures were accompanied by vocalization (non-language sounds); the apes’ gestures rarely were.

“This finding suggests that the ability to combine gesture and vocalization may have been important for the evolution of language,” Greenfield said.

The researchers conclude that humans inherited a language of gestures and a latent capacity for learning symbolic language from the last ancestor we share with our chimpanzee and bonobo relatives — an ancestor that lived approximately 6 million years ago.

The evolution of human language built on capacities that were already present in the common ancestor of the three species, the psychologists report.

“Our cross-species comparison provides insights into the communicative potential of our common ancestor,” Gillespie-Lynch said.

The article is titled “A cross-species study of gesture and its role in symbolic development: implications for the gestural theory of language evolution.” Other co-authors were Yunping Feng and Heidi Lyn.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2013-06/uoc–hsa060313.php

Study: http://journal.frontiersin.org/article/10.3389/fpsyg.2013.00160/full