How does the brain make sense out of a jumble of words?

February 21st, 2009 - 6:23 pm ICT by IANS  

London, Feb 21 (IANS) How does the brain turn seemingly random sounds and letters into sentences with clear meaning?
Psychologist Jos J.A. Van Berkum from the Max Planck Institute in The Netherlands described recent experiments using brain waves to understand how we are able to make sense of sentences.

In these experiments, Van Berkum and his colleagues examined event related potentials (or ERPs) as people read or heard critical sentences as part of a longer text, or placed in some other type of context.

ERPs are changes in brain activity that occur when we hear a certain stimulus, such as a tone or a word. Due to their speed, ERPs are useful for detecting the incredibly fast processes involved in understanding language.

Analysis of the ERPs has consistently indicated just how quickly the brain is able to relate unfolding sentences to earlier ones. For example, Van Berkum and colleagues have shown that listeners only need a fraction of a second to determine that a word is out of place, given what the wider story is about.

As soon as listeners hear an unexpected word, their brain generates a specific ERP, the N400 effect (so named because it is a negative deflection peaking around 400 milliseconds). And even more interesting, this ERP will usually occur before the word is even finished being spoken.

Besides the words themselves, the person speaking them is a crucial component in understanding what is being said. Van Berkum also saw an N400 effect occurring very rapidly when the content of a statement being spoken did not match with the voice of the speaker, for example “I have a large tattoo on my back” in an upper-class accent or “I like olives” in a young child’s voice.

These findings suggest that the brain very quickly classifies someone based on what their voice sounds like and also makes use of social stereotypes to interpret the meaning of what is being said, according to a Max Planck release.

But how does the language part of the brain act so fast? Recent findings suggest that as we read or have a conversation, our brains are continuously trying to predict upcoming information.

These findings were published in Current Directions in Psychological Science.

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