likely related to how trained and some untrained dogs sense what you are up to consciously or not (yet).

brains smell/decode info that we don't have an actual odor (but receptors) for.

it's also why (some) pets and animals react to their human's mood/attitude and short-, mid-, long-term stress (and other) hormone levels.

some people get their energy drained by persons that they are not even aware of being in proximity (e.g. dad got home after work while child is wearing headphones). it can become a matter of good or bad resilience, too, and some brains can develop defence mechanisms by mere exposure while others can't, which is likely (definitely) entangled in/with hormone metabolisms.