This makes sense considering that they capture much less information than the other two high dimensional descriptive vectors, as they do not represent the complex properties of the words, only a numerical assessment of their likelihood.
brain imaging studies have suggested that during reading, the brain (a) continuously builds a context from the successive words and every time it encounters a word it (b) fetches its properties from memory and (c) integrates it with the previous context with a degree of effort that is inversely proportional to how probable the word is.