The brain is constantly trying to guess the next word, both when reading a book and listening to speech. The discovery comes from a study published in the scientific journal PNAS.
Neuroscience already had an idea that this happened, but the scientific evidence so far was indirect and restricted to artificial situations, which motivated the team to understand exactly how this works and to test the brain’s guessing impetus in different situations.
The researchers analyzed the brain activity of people listening to investigative stories and used a computer model to calculate the degree of unpredictability for each written word.
As the article comments, what happens is that, for each word or sound, the brain makes detailed statistical expectations and ends up being extremely sensitive to the degree of unpredictability: the brain response is stronger whenever a word is unexpected in context.
“The brain sometimes mentally finishes someone else’s sentences, for example, if they start to speak very slowly, stutter, or are unable to think of a word. But what we show here is that our brain is constantly guessing the words. ‘predictive machinery’ is always on,” the researchers point out.
The researchers mention that the brain does something comparable to speech recognition software, which is also constantly making predictions. Another example is the autofill function on your phone. But brains don’t just predict words. These predictions happen on many different levels, from abstract meaning to specific sounds.
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