Ever wondered how we can understand a spoken sentence on the spot so fast? Well, it involves a huge and complex set of mental calculations by our brains which we are now a step closer to understanding, thanks to scientists from the University of Cambridge.

The scientists have devised new computational models of the meaning of words and tested them directly against real-time brain activity in volunteers.

"Our ability to put words into context, depending on the other words around them, is an immediate process and it's thanks to the best computer we've ever known: the brain in our head. It's something we haven't yet managed to fully replicate in computers because it is still so poorly understood," said Lorraine Tyler, Director of the Centre for Speech, Language and the Brain at the University of Cambridge, which ran the study.

In understanding speech, there are processes involved in what is known as "semantic composition." This is where the brain applies meaning to the words in a sentence so that they make sense as taken in context. The study revealed the detailed real-time processes that allow this to take place in our brains.

We listen at 125-250 words per minute, but think at 1000-3000 words per minute. Image by Robin Higgins from Pixabay

The volunteers were made to say simple phrases such as ‘the elderly man ate the apple’ while the researchers observed their brains to track the dynamic flow of information between regions of the brain associated with language.

If you have ever played a game of word association, it is what our brains do when we hear a word such as "eat." We know that the sentence likely has something to do with food and this affects how the following words said are understood. This reveals to us the neural mechanisms supporting the essential property of spoken language: our ability to put together sequences of words into worthwhile expressions, millisecond by millisecond as the speech is heard.

"The way our brain enables us to understand what someone is saying, as they're saying it, is remarkable," said Professor Tyler. "By looking at the real-time flow of information in the brain we've shown how word meanings are being rapidly interpreted and put into context."