The examples always sound like they could be either one to me.
Accepted answer
Ask whether the behavior is **involuntary and triggered**, or **voluntary and consequence-driven**.
**Classical** (Pavlov): an automatic response gets attached to a new stimulus through pairing. The learner is passive — the dog doesn't choose to salivate, and salivation happens *before* anything it does.
**Operant** (Skinner): the learner emits a voluntary behavior, and what follows — reinforcement or punishment — changes how likely that behavior becomes. The consequence comes *after* the behavior.
So: fear of the dentist's drill sound is classical (involuntary anxiety paired with a stimulus). Studying more after a good grade is operant (voluntary behavior strengthened by a consequence).