Scientist have found how quickly the brain is able to relate unfolding sentences to earlier ones. For example, 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 pattern named the N400 effect (so named because it is a negative deflection peaking around 400 milliseconds). And even more interesting, this will usually occur before the word is even finished being spoken.

In addition to the words themselves, the person speaking them is a crucial component in understanding what is being said. The scientist 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 (e.g. "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.