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201515Dec21:28

Small talk of pri­mates could serve an evo­lu­tion­ary need to bond with others

Infor­ma­tion
pub­lished 15 Decem­ber 2015 | mod­i­fied 15 Decem­ber 2015
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Lemur vocalizationWe think of chitchat and small talk as the things peo­ple say to pass the time or kill an awk­ward silence. New research sug­gests, how­ever, that these idle con­ver­sa­tions could be a social-​bonding tool passed down from primates.

Prince­ton Uni­ver­sity researchers found out that social pri­mates use vocal­iza­tions far more selec­tively than sci­en­tists pre­vi­ously thought. They found that ring-​tailed lemurs (Lemur catta) liv­ing in groups pri­mar­ily call and respond to the indi­vid­u­als with which they have close rela­tion­ships. While groom­ing is a com­mon social-​bonding expe­ri­ence for lemurs and other pri­mates, the researchers found that lemurs reserved vocal exchanges for the ani­mals that they groomed most fre­quently. The research find­ings have been pub­lished online on 27 Octo­ber in the jour­nal Ani­mal Behaviour.

Lemurs vocal­ize to essen­tially “groom-​at-​a-​distance” and keep in touch when the group mem­bers they’re clos­est with get sep­a­rated such as when for­ag­ing for food, said first author Ipek Kulahci, who received her Ph.D. in ecol­ogy and evo­lu­tion­ary biol­ogy from Princeton.

Our results indi­cate that when ani­mals respond to each other’s vocal­iza­tions, they are in fact also work­ing on main­tain­ing their social bonds,” said Kulahci.

By exchang­ing vocal­iza­tions, the ani­mals are rein­forc­ing their social bonds even when they are away from each other,” Kulahci said. “This social selec­tiv­ity in vocal­iza­tions is almost equiv­a­lent to how we humans keep in reg­u­lar touch with our close friends and fam­i­lies, but not with every­one we know.”

Peo­ple think that con­ver­sa­tions are like exchang­ing mini-​lectures full of infor­ma­tion. But most of the time we have con­ver­sa­tions and for­get them when we’re done because they’re per­form­ing a purely social function
Asif A. Ghaz­an­far, co-​author, pro­fes­sor of psy­chol­ogy at the Prince­ton Neu­ro­science Institute »

The find­ings could have impli­ca­tions for how sci­en­tists under­stand the evo­lu­tion of pri­mate vocal­iza­tions and human speech, co-​author Ghaz­an­far explained. Exist­ing the­o­ries of lan­guage evo­lu­tion sug­gest that vocal exchanges between pri­mates evolved with group size, he said. As group size increased, groom­ing to form social bonds became too time con­sum­ing, so speech devel­oped to save time while still express­ing familiarity.

Ghaz­an­far and his col­leagues found, how­ever, that vocal­iza­tions occurred inde­pen­dently of group size. The lemurs the researchers stud­ied groomed more as their num­bers increased, but did not nec­es­sar­ily vocal­ize more. These find­ings show a direct con­nec­tion between groom­ing — or famil­iar­ity — and vocal­iza­tion not found before, Ghaz­an­far said.

The Prince­ton research sug­gests that talk­ing, even just casu­ally, is an evo­lu­tion­ary tool for estab­lish­ing close­ness, Ghaz­an­far said.

Talk­ing is a social lubri­cant, not nec­es­sar­ily done to con­vey infor­ma­tion, but to estab­lish famil­iar­ity,” he said. “I think these vocal­iza­tions are equiv­a­lent to the chitchat that we do. Peo­ple think that con­ver­sa­tions are like exchang­ing mini-​lectures full of infor­ma­tion. But most of the time we have con­ver­sa­tions and for­get them when we’re done because they’re per­form­ing a purely social function.”

Led by Kulahci, the researchers stud­ied the vocal inter­ac­tions and groom­ing net­works of var­i­ous groups of ring-​tailed lemurs liv­ing at Duke University’s Lemur Cen­ter and on St. Cather­ines Island in Geor­gia. They found that groom­ing itself was selec­tive and per­formed only between cer­tain indi­vid­u­als. Vocal­iza­tions went even fur­ther in selec­tiv­ity — the ani­mals responded only to the calls of those they groomed most often.

The researchers recorded the vocal­iza­tions of indi­vid­ual lemurs and played them back to the group. Again, only lemurs that shared a close groom­ing rela­tion­ship with the indi­vid­ual emit­ting the call responded, even if the lemur mak­ing the vocal­iza­tion was not nearby. This last point empha­sizes that strong social bonds are indi­cated by vocal exchanges, the researchers wrote, because the vocal­iz­ing lemur could not be seen or smelled by the ani­mal that replied.

The lemurs’ use of groom­ing and vocal­iza­tion to estab­lish greater lev­els of famil­iar­ity could help sci­en­tists under­stand how forms of com­mu­ni­ca­tion are inter­re­lated, Ruben­stein said. Like lemurs, humans inter­act using var­i­ous ver­bal and phys­i­cal actions that are com­ple­men­tary and contextual.

The use of dif­fer­ent chan­nels of com­mu­ni­ca­tion is a big deal and it is some­thing we humans do all the time,” Ruben­stein said.

We raise our voice and use our hands when mak­ing an emphatic point, but stick to voice only when not par­tic­u­larly excited or the sit­u­a­tion is less urgent,” he said. “This research helps open doors about the func­tion of multi-​modal sig­nalling in the sense that tac­tile ver­sus acoustic forms of com­mu­ni­ca­tion are rein­forc­ing each other but in ways that were dif­fer­ent from expected.”

Beau­ti­ful footage of some of the lemur species that still exist, but are endan­gered, on the island of Madagascar:


(Source: Ryan M. Bolton YouTube chan­nel)


(Source: Prince­ton Uni­ver­sity news release, 14.12.2015)


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