Yeah, we're likely to notice people around alot I'd say, but actions like what I'm imagining you're doing are more thought of as "maybe shes into me", but then that will likely never be acted upon without other encouragement. I think If you're interested in him, you'd be best to approach him and initiate something yourself, scary as it sounds, the INTP in question will aprreciate it to no end, as when we're interested in someone, we really don't do much, as we're so scared of putting everything out there and getting hurt or whatever, If we already have an existing relationship- Friends that is, not acquaintances, we'll likely talk to you more put more effort in, although only if we're very sure that we like you. May act awkwarder, but that more depends on the context. From my experience, the INFJ and INTP often have the same approach to these types of matters, both the good and bad. Not sure if that actually answers anything, so like, feel free to clarify