Inside the human cerebral cortex, an interconnected system of areas has developed to interpret language. These areas are regularly activated whenever individuals engage with their mother tongue or any language in which they possess proficiency.

A recent investigation conducted by researchers at MIT indicates that this system is also responsive to entirely fabricated languages, such as Esperanto, which was conceived in the 1880s to encourage global communication, as well as to languages created for television programs like “Star Trek” and “Game of Thrones.”

In order to examine how the brain reacts to these synthetic languages, neuroscientists from MIT gathered nearly 50 speakers of these languages over a single weekend. Utilizing functional magnetic resonance imaging (fMRI), the investigators observed that when participants listened to a fabricated language in which they were skilled, the same cerebral areas illuminated as those activated when they processed their first language.

“We discover that constructed languages significantly engage the same system as natural languages, implying that the essential characteristic required to activate the system may relate to the types of meanings both categories of languages can convey,” states Evelina Fedorenko, an associate professor of neuroscience at MIT, affiliated with MIT’s McGovern Institute for Brain Research and the principal author of the research.

The results assist in delineating some of the fundamental attributes of language, according to the researchers, and imply that it isn’t requisite for languages to have organically developed over extended periods or to have numerous speakers.

“This aids in refining the inquiry of what constitutes a language, and doing so empirically, by evaluating how our brain reacts to stimuli that might or might not resemble language,” explains Saima Malik-Moraleda, a postdoctoral researcher at MIT and the primary author of the article, which is published this week in the Proceedings of the National Academy of Sciences.

Gathering the conlang community

In contrast to natural languages, which develop within societies and adapt over time, constructed languages, or “conlangs,” are generally devised by an individual who determines the sounds to be utilized, how to designate various concepts, and the grammatical regulations.

Esperanto, the most widely utilized conlang, was established in 1887 by Ludwik Zamenhof, who envisioned it as a universal language for global interaction. Currently, it is estimated that approximately 60,000 individuals worldwide are proficient in Esperanto.

In prior research, Fedorenko and her team discovered that programming languages, such as Python — another variant of invented language — fail to activate the cerebral network employed for processing natural language. Instead, individuals who read computer code depend on the so-called multiple demand network, a cognitive system often utilized for challenging mental tasks.

Fedorenko and colleagues have also examined how the brain reacts to other stimuli that share characteristics with language, including music and nonverbal communication such as gestures and facial expressions.

“We dedicated significant time to investigating these various types of stimuli, repeatedly finding that none of them engage the mechanisms for language processing,” Fedorenko remarks. “This raises the question of what it is that natural languages possess that these alternative systems do not?”

This prompted the researchers to consider whether fabricated languages like Esperanto would be processed similarly to programming languages or more akin to natural languages. Analogous to programming languages, constructed languages are designed by an individual for a particular aim without the organic development within a community. Nevertheless, differing from programming languages, both conlangs and natural languages can be utilized to communicate meanings regarding the external environment or the speaker’s internal feelings.

To investigate how the brain processes conlangs, the researchers invited speakers of Esperanto and several other constructed languages to MIT for a weekend conference in November 2022. The other languages included Klingon (from “Star Trek”), Na’vi (from “Avatar”), and two languages from “Game of Thrones” (High Valyrian and Dothraki). For all of these languages, resources are available for learners, and for Esperanto, Klingon, and High Valyrian, there is even a Duolingo application accessible.

“It was an incredibly enjoyable event where all communities gathered to engage, and over the weekend, we compiled all the data,” states Malik-Moraleda, who co-led the data collection with former MIT postbaccalaureate Maya Taliaferro, now a PhD candidate at New York University.

During this gathering, which also included lectures from several conlang creators, the researchers utilized fMRI to scan 44 conlang speakers while they listened to sentences from the constructed language in which they were proficient. The creators of these languages — who are co-authors on the paper — contributed to the formulation of the sentences that were presented to the participants.

While in the scanner, participants also either listened to or read sentences in their native language and engaged in some non-linguistic tasks for comparison. The researchers found that when individuals listened to a conlang, the same language processing regions of the brain were activated as when they listened to their first language.

Shared characteristics

The results help to pinpoint some of the essential features necessary for engaging the brain’s language processing regions, the researchers remark. One of the primary traits influencing language responses appears to be the ability to convey meanings related to inner and outer experiences — a characteristic shared by both natural and constructed languages, but not programming languages.

Some additional attributes of natural languages, which are not present in constructed languages, do not appear to be essential for eliciting a response in the language network.

“It is irrelevant whether the language is created and molded over time by a community of speakers because these constructed languages are not,” Malik-Moraleda states. “The age of the languages is also inconsequential, as conlangs that are merely a decade old activate the same brain regions as natural languages that have existed for many centuries.”

To further specify the characteristics of language that stimulate the brain’s language network, Fedorenko’s laboratory is now planning to investigate how the brain reacts to a conlang named Lojban, developed by the Logical Language Group in the 1990s, created to eliminate ambiguity in meanings and enhance communication efficiency.

This research was supported by MIT’s McGovern Institute for Brain Research, the Department of Brain and Cognitive Sciences, the Simons Center for the Social Brain, the Frederick A. and Carole J. Middleton Career Development Professorship, and the U.S. National Institutes of Health.