I have seen subjects names like "Cognitive Sciences" are wrote both with and without capitals, like "cognitive sciences". Are there a criteria to this respect?
There is no need to capitalise when it is simply the name of a subject or discipline. In such a context it would be acting as a common noun, so would not need capitals.
It would be capitalised if referring to a specific course, department, etc, where it is acting as a proper noun.
Professor Smith is a renowned expert in cognitive sciences. Professor Smith works in the university's Cognitive Sciences department. I am studying cognitive sciences as part of my degree. My lecturer for the Cognitive Sciences module is Professor Smith.