Khan Academy: Test Prep: Mcat: Behavior: Learning: Classical and Operant Conditioning Article

Conditioning is a type of learning that links some sort of trigger or stimulus to a human behavior or response. When psychology was first starting as a field, scientists felt they couldn't objectively describe what was going on in people's heads. However, they could observe behaviors so that's what they focused on in their experiments. The major theories about learning come from the conclusions drawn from these experiments.