06/03/2009 by admin.

A week or so back there was an item in ScienceDaily, How we think before we speak: making sense of sentences. (here) I was reminded of it when I encountered an ‘up the garden path’ remark.

Linguists have a method of diagramming a sentence to make its grammar clear. If the sentence can be successfully diagrammed then it is grammatical and each word is given its function in the sentence. Diagramming works well with written language. But with spoken language or very difficult written language, it is possible to be misled at the beginning of a sentence so that the sentence is parsed in a way that makes no sense by the end of the sentence. It has to be re-parsed to make it understandable. This is a sentence that leads one ‘up the garden path’. With my bias to consider spoken language as real language and written language as somewhat artificial, I think of garden path sentences as ungrammatical even if, when the whole sentence is available, it can be diagrammed successfully. Wikipedia supplied these examples:

“The old man the boat.”

(The elderly are the crew of the boat)

“The man whistling tunes pianos.”

(The man who is whistling also tunes pianos)

“The cotton clothing is made of grows in Mississippi.”

(The cotton that clothing is made of is grown in Mississippi)

Back to the article – it shows how the listener predicts what the speaker is going to say next.

In … Current Directions in Psychological Science Jos J.A. Van Berkum …describes recent experiments using brain waves to understand how we are able to make sense of sentences. (They) 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…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…Van Berkum speculates that “the linguistic brain seems much more ‘messy’ and opportunistic than originally believed, taking any partial cue that seems to bear on interpretation into account as soon as it can.”

But how does the language brain act so fast? Recent findings suggest that, as we read or have a conversation, our brains are continuously trying to predict upcoming information. Van Berkum suggests that this anticipation is a combination of a detailed analysis about what has been said before with taking ‘quick-and-dirty’ shortcuts to figure out what, most likely, the next bit of information will be.

One important element in keeping up with a conversation is knowing what or whom speakers are actually referring to. For example, when we hear the statement, “David praised Linda because. . .,” we expect to find out more about Linda, not David. Van Berkum and colleagues showed that when listeners heard “David praised Linda because he. . .,” there was a very strong ERP effect occurring with the word “he,” of the type that is also elicited by grammatical errors. Although the pronoun is grammatically correct in this statement, the ERP occurred because the brain was just not expecting it. This suggests that the brain will sometimes ignore the rules of grammar when trying to comprehend sentences.

These findings reveal that, as we make sense of an unfolding sentence, our brains very rapidly draw upon a wide range of information, including what was stated previously and who the speaker is, in helping us understand what is being said to us. Sentence understanding is not just about diligently combining stored word meanings. The brain rapidly throws in everything it knows, and it is always looking ahead.

This implies that we experience a prediction from just past information into the near future – so that our ‘present’ is approximately what should be happening ‘now’. This feed forward has been shown in vision by the nature of illusions and is now shown in hearing. It also appears to be true for motor movement.

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