Chomsky showed that humans have a (very often subconscious) sense of grammatical structure. This idea of a special structure could be evidence of Universal Grammar. Let’s think about some simple sentences:
1. Taro hates him.
2. Taro hates himself.
A pronoun like him cannot be matched with the subject Taro in 1. Personal pronouns need to match an expression outside a tensed clause. So in 1, him cannot be Taro. However, expressions like himself (these are called reflexive pronouns) must be matched with an expression close
This kind of example shows that human language involves a subconscious awareness of structure that is quite puzzling. We might consider it evidence that human language involves special rules that are different from our normal mental processes.
Chomsky, N. (2013) Problems of projection. Lingua 130, 33-49.