Scientists find 'missing link' behind first human languages

A new study has shown, for the first time, that humans recognize the intended meanings of iconic vocalizations — basic sounds made by people to represent specific objects, entities and actions — regardless of the language they speak. 

These vocalizations, such as the imitation of snoring to denote sleep, or roaring to denote a tiger, could have played a crucial role in the development of the first human languages, according to the researchers.

The finding contrasts with the prior assumption that physical gestures and signals drove the development of human language.

Related: Cracking codes: 5 ancient languages yet to be deciphered

"People around the world, whatever their linguistic or cultural background, were remarkably good at being able to guess the meanings of these different vocalizations," senior author Marcus Perlman, a linguist at the University of Birmingham in England, told Live Science. "This could have big implications for how spoken languages got off the ground."

Iconic vocalizations 

In an online experiment, researchers exposed 843 participants, who spoke 25 different languages among them, to iconic vocalizations representing 30 meanings that would have been key for the survival of early humans. The participants then had to match the sound to one of six words, including the intended meaning. 

The intended meanings for vocalizations were grouped into six main categories: animate entities (child, man, woman, tiger, snake, deer), inanimate entities (knife, fire, rock, water, meat, fruit), actions (gather, cook, hide, cut, pound, hunt, eat, sleep), properties (dull, sharp, big, small, good, bad), quantifiers (one, many) and demonstratives (this, that).

Researchers obtained these vocalizations through an online contest where, in exchange for prizes, people could submit basic sounds that they felt best represented different words. Everyone who submitted a vocalization spoke English.

In the experiment, people accurately identified the meaning of these vocalizations 64.6% of the time, on average. The most recognizable vocalization was that for "sleep," which people identified with 98.6% accuracy. The least recognizable was the demonstrative "that," with an accuracy of 34.5%, although it was still well over the 16.7% (one in six) expected by chance. 

In general, people understood the vocalizations of actions and entities better than those for properties and demonstratives. "These recognizable sounds [actions and entities] are probably associated with these meanings across cultures," Perlman said. "In others, there's probably more variability over precisely what that sound is."

Out of the 25 languages spoken by participants, speakers of 20 languages correctly guessed the meaning of each vocalization on average, speakers of four of the languages did so for all but one vocalization and speakers of the remaining language did so for all but two. The language speakers with the lowest accuracy were Thai speakers at an average of 52.1% and the best performing language speakers were English speakers with an average accuracy of 74.1%.

In a second, smaller field experiment that involved just 12 of the most basic vocalizations, people who used spoken languages with no formal writing system, such as the Indigenous Palikúr of the Amazon rainforest — also demonstrated an understanding of vocalizations by pointing to pictures of the correct meanings after hearing them. They managed to suss out the meaning without any written or spoken prompts, well above what was expected by chance.

Missing link

Until now, researchers had assumed that human languages developed through the use of iconic gestures — such as wiggling your arm to mimic the movement of a snake —  and other physical signals, Perlman said. After communicating with gestures, early humans would then have gradually added spoken words that would have replaced these physical signals, according to this theory.

"It makes sense," Perlman said. "If you go to a country where you don't speak the language, the intuitive way to communicate is to gesture what you're trying to express."

However, our ability to interpret the meaning of iconic vocalizations suggests humans may not have needed physical gestures to create words. Instead, vocalizations may have been the first building blocks of languages, and physical gestures may have been added to individual words afterward, Perlman said.

However, not all researchers agree with this idea.

"A more compelling argument for the role of iconic representation in language evolution comes from manual gestures," Michael Corballis, a psychologist who specializes in language evolution at the University of Auckland in New Zealand, told Live Science. "Sign languages have a more obvious iconic element than speech does." Although, "there is increasing evidence of an iconic component in human speech," Corballis said.

In reality, the development of the first languages would have taken hundreds or even thousands of years, and it's likely that a combination of vocalizations and gestures played a part, Perlman said. "We have hands and a voice," Perlman said. "And we have been communicating with both for many millions of years." 

"I agree that a multimodal origin is the most plausible," Michael Arbib, a language expert and computational neuroscientist at University of Southern Carolina, told Live Science. "Certain entities have distinctive sounds which favor the use of sound symbolism for their origin, whereas many others are more hospitable to pantomime."

But as with the chicken and the egg, it is hard to definitively say which came first: vocalizations or gestures. 

"The next step would be to see whether people can understand sounds produced by people from different cultures and language backgrounds," beyond English-speaking ones, Perlman said. After that, future studies "would explore more complex meanings and vocalizations" to see how early humans might have developed the first languages from these sounds, Perlman said.

Future studies should also include comparisons between vocalizations and gestures to see how well they stack up against each other and see which words suit each type of communication, Arbib said. 

Understanding the origins of human language is important because language is such a fundamental part of what it means to be human, Perlman said. "It speaks to the human condition, our history, our relationship with the world around us and the essence of who we are."

The study was published online May 12 in the journal Scientific Reports.

Originally published on Live Science.