What term denotes an energy change that affects an organism through its receptor cells?

• A. Stimulus
• B. Stimulus Class
• C. Response Maintenance
• D. Schedule Thinning

Answer: (A)

The main idea here is understanding what a stimulus is. A stimulus is any energy change in the environment or inside the body that affects an organism by activating receptor cells in sensory systems. When light, sound, a chemical taste, or touch changes the organism’s sensory receptors, those changes are stimuli that can influence perception and behavior. The term describes the energy input reaching the senses, not a group of similar stimuli (that would be a stimulus class) or processes related to reinforcement or maintenance (like response maintenance or schedule thinning). So the energy change detected by receptors is the stimulus.