First things first

日期:2017-07-14 05:25:16 作者:邰勾 阅读:

By Alison Motluk THE brain works harder when gearing up to understand sentences that present information out of chronological order, say scientists in Germany and California. They have measured the effect at work just milliseconds after people start reading a sentence. Thomas Münte of the Medical College of Hannover and his colleagues from the University of California at San Diego took 24 volunteers and asked them to read 120 sentences. Using electrodes attached to the volunteers’ scalps, they tracked the electrical activity in their brains. The researchers were particularly interested in how readers responded to sentences beginning with the words “before” and “after”. When they read the sentence, “Before the psychologist submitted the paper, the journal changed its policy,” for instance, there was a sharp increase in activity in the left frontal cortex, a region associated with working memory. This response occurred within a mere 300 milliseconds. When the word “after” was substituted for “before” in the same sentence, activity also increased, but by a smaller amount. This indicates that less working memory is required for “after” sentences, the researchers say. Münte reckons that because people naturally think in terms of sequential events, more mental processing is required to make sense of sentences in which this order is disrupted (Nature, vol 395, p 71). “After” sentences fit our chronological view, whereas “before” sentences do not, so need extra computation. “You have to keep the first chunk in working memory,” says Münte. The size of the difference between the responses to the two word cues gives an indication of a person’s level of understanding,