The placebo effect best illustrates the impact of ________ on feelings and behaviors.

A) the double-blind procedure
B) random sampling
C) positive expectations
D) hindsight bias

The placebo effect occurs when someone experiences a positive outcome from a treatment that has no known medical benefit. This effect is often attributed to the patient's positive expectations about the treatment, showing the impact of positive expectations on feelings and behaviors. The double-blind procedure and random sampling are research methods that do not directly relate to the placebo effect, and hindsight bias refers to the tendency to overestimate one's ability to have predicted an outcome after the fact.