The term irradiation, used by Pavlov, refers to which phenomenon?

• A. Acquisition
• B. Stimulus discrimination
• C. Stimulus generalization
• D. Extinction

Answer: (C)

The concept being tested is stimulus generalization. In Pavlov’s conditioning work, once a dog learns to salivate to a specific conditioned stimulus (like a particular bell), the response tends to spread to other similar stimuli as well. The term irradiation captures this spreading effect—the conditioned response radiates outward to stimuli that resemble the original CS, even without training for those new stimuli. This is different from acquisition (the initial learning of the CS–US pairing), extinction (the weakening of the response when the CS is no longer paired with the US), or discrimination (the ability to tell apart similar stimuli and respond only to the exact CS).