Researchers have found fault in a study published earlier this year that claimed chimpanzees could learn local language from each other. After taking a closer look at the study, researchers from New York University (NYU), the German Primate Center in Göttingen, and the University of Kent have concluded the study actually misrepresents what the data shows, according to a news release.
In the original study, published in Current Biology, researchers examined two sets of chimpanzees at the Edinburgh Zoo. While one group of the chimpanzees had been living at the zoo for several years, the other group had recently arrived from the Beekse Bergen Safari Park in the Netherlands. Following the move, researchers monitored the interactions of the two groups over the course of three years. As a result, they claimed the newcomers had actually altered their vocalizations in order to communicate with the natives about a common object, in this case apples.
However the new analysis, which has also been published in Current Biology, points out two flaws: the causes behind changing vocalizations and the the fact that the original researchers overlooked how similar each group's vocalizations were to begin with. This suggests the change was not really that significant, according to the release.
"There are a number of problems with the original study," James Higham, an assistant professor in NYU's Department of Anthropology and a co-author of the new analysis, explained.
"Our first point relates to changes in arousal, which the authors did not control for and which could prompt false conclusions about the causes behind vocal changes," Julia Fischer, lead author of the new analysis from the German Primate Center, added. "The Dutch chimpanzees may have given slightly different calls to the Edinburgh chimps, and then changed their calls, due simply to differences in their original feeding environments and diet, and then the subsequent changes in these following their move to Edinburgh."
This simply means the animals' didn't necessarily change their vocalizations because they needed to communicate about the apples. Instead, the move from different environments alone could have altered the nature of their vocalizations. For example, if the chimpanzees used a higher-pitched call when moving to the Edinburgh Zoo it may represent feelings of excitement, not necessarily a new way of communicating.
The new analysis also revealed the chimpanzees' vocalizations were not all that distinct in the first place.
"Closer inspection of the data reveals that both groups largely overlapped in the range of calls they were originally giving in response to apples, with only a few calls of the Dutch chimpanzees outside the range of the calls given by the Edinburgh chimpanzees," Brandon Wheeler, co-author of the new analysis and a biological anthropologist at the University of Kent, said in the university's release. "There is some statistically significant but biologically weak change of the calls over time following the move of the Dutch chimpanzees to Edinburgh, but such social modulation is a well-known phenomenon in animal vocalizations that has been found in most primate calls--and even in the calls of goats."
So we're back to square one in our understanding of vocal learning and the evolution of language.
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