I watched myself brush my hair in the mirror.

Intensive or Reflexive

The sentence is reflexive pronoun.

Explanation:

The reflexive pronoun and intensive pronoun have same words, namely, 'himself, myself, yourself, ourselves, themselves, herself, and itself'. The major difference between these two pronouns is the usage of them in the sentences.

A reflexive pronoun will add the emphasis on the subject. Therefore, in a sentence with a reflexive pronoun, the subject and object will be the same. Therefore, in the question, 'I watched myself brush my hair in the mirror.' the object and subject are the same.

Subject - I; Object - myself.

Intensive.

Explanation:

We can know that a pronoun is intensive if when removed from the sentence, it still makes sense. In this case, if we remove "I", the sentence is still understandable, watched myself brush my hair in the mirror.