Watching the brain when processing language

Why are we able to follow a complex conversation while even apes can only understand individual words? German researchers from the Max Planck Institute have used the fMRI (functional magnetic resonance imaging) technique to discover that our brains are hard-wired for grammar.

Why are we able to follow a complex conversation while even apes can only understand individual words? German researchers from the Max Planck Institute have used the fMRI (functional magnetic resonance imaging) technique to discover that our brains are hard-wired for grammar. They found that simple language structures are processed by an area of our brain that we share with apes. On the contrary, complex language structures are processed by a 'younger' part or our brains that apes don't have.

First, what are the differences between simple and complex language structures?

The human ability to apply complex linguistic rules has been held responsible for the fact that, in contrast to other species, we can produce and understand long sentences. When analysing language rules (syntax), one discovers two fundamentally different grammatical patterns.
A simple rule governs the establishment of typical (probable) connections between words, like between article and noun ("a song") in contrast to article and verb ("a pleases"). The probability for a noun to follow an article is very high, while the probability of a following verb is very low.
However, in order to understand longer sentences, a complex structural model is required - what is called a "hierarchy". Hierarchical dependencies serve to connect parts of a sentence - for example "around" an inserted subordinate clause: "The song [that the boy sang] pleased the teacher".

The researchers decided to use the fMRI (functional magnetic resonance imaging) technique to see which areas or our brains were activated when processing various language structures.

Below is an image showing this brain activity when processing different linguistic rules (Credit for image and caption: Max Planck Institute for Human Cognitive and Neurosciences). Here is a link to a larger version.

Brain activity when processing linguistic rules

[Here is a] comparison of the activation and structural connections of brain areas during the processing of simple or complex linguistic rules. A: The frontal operculum engages in the processing of both rule types (upper image).By contrast, Broca's area becomes active for complex rules only (lower image). B: The frontal operculum is linked to the anterior portion of the temporal lobe via the fasciculus uncinatus. Right: Broca's Area is connected with the posterior portion of the temporal lobe via the fasciculus longitudialis superior.

For their experiments, the researchers invented and used artificial grammars. Here is a short description.

The scientists created artificial grammars with meaningless but structured syllables (e.g., de bo gi to). The ordering of these syllables was based upon either the simple rule ("local probability") or the complex rule ("hierarchy"). The syllables were divided into two categories. Syllables of category A ended with (in German) phonetically bright vowels (de, gi, le), and category B with dark vowels (bo, fo, gu).
The simple rule involved alternating sequences from categories A and B (e.g., AB AB = de bo gi ku); the complex rules on the other hand required hierarchies to link both categories (e.g., AA BB = de gi ku bo). This principle was meant to reduce grammar into the simplest formal rules.

For more information, this research work has been published by the Proceedings of the National Academy of Sciences under the title "The brain differentiates human and non-human grammars: Functional localization and structural connectivity" (Volume 103, Number 7, Pages 2458-2463, February 14, 2006). Here is a link to the abstract of this paper.

And for another point of view about this research work, you also should read an article by Maggie Wittlin published by Seed Magazine on February 14, 2006, "Researchers find elements of grammar are hardwired into the human brain," which focuses on how " core elements of grammar—subjects, objects and verbs—are integral parts of human cognition and are present in every language, even those developed in isolation." Here is a short quote.

Elissa Newport, a cognitive science and linguistics professor at the University of Rochester, and Marie Coppola, a University of Chicago post-doc, studied the sign systems of three deaf young adults in Nicaragua who had previously had no contact with a deaf community. They found all three had integrated the complicated, formal ideas of subjects, objects and verbs into their languages, even though no one had taught them language.

But what are the practical implications of this research? It will simply help us to better understand the human language faculty.

Sources: Max Planck Society Press Release, February 16, 2006; and various web sites

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