A simple chat with a neighbor on the street may last only long enough to make you a few minutes late to work. But it still requires a lot of complex brain power to pull off.
To really catch the meaning of what a conversation partner is saying, you’ll have to infer the unspoken, hidden meanings lurking behind the words. That may mean deciphering metaphors about brewing storms or black sheep, detecting irony or white lies, getting dad jokes, or listening for changes in inflection. In lengthier chats, your brain may have to do all of that.
In the scientific literature, this sort of inference is known as pragmatic language ability, but scientists have not understood much about how it works. New research from MIT cognitive neuroscientist Evelina Fedorenko and her colleagues shows that these so-called pragmatic language abilities can be grouped together into three categories based on the kinds of inference they require, and that these categories may have similar underlying neural processes. They published their findings in the Proceedings of the National Academy of Sciences.
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“Pragmatics is trying to reason about why somebody might say something, and what is the message they’re trying to convey given that they put it in this particular way,” said Fedorenko, who runs a lab at MIT’s McGovern Institute for Brain Research, in a statement.
To gather their intelligence, the scientists tested 376 study participants on an 8-hour battery of 20 nonliteral comprehension tasks—involving subjects such as irony, indirect requests, polite deceits, metaphor, and humor—to try to detect individual differences in performance.
They found that different participants’ strengths could be grouped into the following categories: grasping social conventions, interpreting intonation, and making causal inferences based on knowledge of the world. They then replicated their findings in 400 new participants, and also found that general intelligence and auditory processing abilities did not affect the results.
“Language is about getting meanings across, and that often requires taking into account many different kinds of information—such as the social context, the visual context, or the present topic of the conversation,” Fedorenko added.
Understanding social conventions, the authors point out, requires reasoning about others’ mental states and helps people maintain rapport and “save face.” Irony, for example, has been argued to allow a speaker to express a negative viewpoint without imposing on the other person. Intonation allows a speaker to express emotional states and to convey nuances in meaning. And reasoning about the world is obviously a critical skill in many life situations.
In future work, the researchers said they want to use brain imaging to see whether the three categories correspond with activity in specific brain regions.
The findings could help clinicians understand why some people with conditions such as autism have trouble with certain components of communication, and help scientists design behavioral and brain imaging studies that can better tease apart how nonverbal communication works.
They want to bring the unspoken word into the spotlight. 
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