A biological engine for human language


April 18, 2014
Brain & Behavior

For more than a decade, North­eastern psy­chology pro­fessor Iris Berent has focused her research on one cen­tral ques­tion: What makes human lan­guage so spe­cial? So far, she’s addressed that ques­tion by con­ducting exper­i­ments on speakers of lan­guages as diverse as Hebrew and Amer­ican Sign Language.

Through this research, she’s uncov­ered some sur­prising things. For instance, her work has shown that regard­less of our mother tongue, we prefer cer­tain lin­guistic struc­tures to others. Despite sig­nif­i­cant dif­fer­ences between lan­guages as unre­lated as Korean and Spanish, all of them seem to share the same set of unwritten rules that dic­tate how sounds can be arranged to form words.

In a study pub­lished in 2007, her team showed that all spoken lan­guages favor cer­tain syl­la­bles. For instance, syl­la­bles such as “lbif” are much less common across lan­guages than syl­la­bles such as “blif.” A later study showed that people are sen­si­tive to this rule even if nei­ther of those syl­la­bles occurs in their language.

Still, a ques­tion has nagged at the back of Berent’s mind: Are these rules bio­log­i­cally hard­wired into the brain? As she put it, “Is there any engine in the brain that cares about this thing and, if so, then what kind of engine is it?”

New research from Berent’s lab, pub­lished Thursday in the journal PLOS ONE, sug­gests that’s exactly the case. For the first time, Berent’s team looked at brain activity while asking par­tic­i­pants to listen to non­sense words that are rep­re­sen­ta­tive of this hier­archy of syl­la­bles that occur across human languages.

The research fol­lows on the heels of a paper co-​​authored by Berent and pub­lished ear­lier this month in the journal Pro­ceed­ings of the National Academy of Sci­ence that exam­ined the brains of new­born babies. The same trend appeared in that research as well, sug­gesting that the human brain forms lan­guages based on an innate set of lin­guistic rules.

In the PLOS study, con­ducted in col­lab­o­ra­tion with researchers at Har­vard Med­ical School, Eng­lish speakers heard var­ious types of syl­la­bles, most of which don’t occur in their native lan­guage. But they occur—at varying frequencies—in other lan­guages. Some, such as bnif, are common across lan­guages; others, such as bdif, are less common, and a select few, such as ibif, are out­right rare.

Par­tic­i­pants hooked up to brain imaging machines heard these syl­la­bles along with sim­ilar non­sense words with two syllables—for instance, benif, bedif, and lebif—and were asked to indi­cate whether the “word” they had heard included one syl­lable or two.

The results showed that as the syl­lable became less fre­quent across lan­guages, Eng­lish speakers had greater dif­fi­culty iden­ti­fying it. Remark­ably, so did their brains. Syl­la­bles that are “worse” along the hierarchy—lbif, for example—caused the brain to work harder than “better” syl­la­bles such as bnif.

Prior to these results, Berent noted, sev­eral hypotheses could have explained the behav­ioral data, including exclusively-​​auditory (“lbif is hard to hear”) or exclusively-​​memory based expla­na­tions (“lbif is not sim­ilar to any Eng­lish words”). If those hypotheses were cor­rect, they would have resulted in acti­va­tion only in the parts of the brain that are respon­sible for audi­tion or word mem­o­ries, respectively.

The new research shows activity in a brain region called Broca’s area. While this region is not exclu­sively ded­i­cated to lin­guistic activity, it is cen­tral to those processes. “If there were lin­guistic uni­ver­sals in the brain,” Berent said, “this is exactly what it would look like.”
– See more at: http://www.northeastern.edu/news/2014/04/berent/#sthash.WxUQEwIW.dpuf

A biological engine for human language

A biological engine for human language

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