An arbitrary stimulus class consists of stimuli that do not share a physical feature but evoke the same label or response.

• A. True
• B. False
• C. They share a common color
• D. They are perceptually similar

Answer: (A)

An arbitrary stimulus class is defined by function, not by appearance. It groups stimuli that do not share physical features but all evoke the same label or response because of the learner’s training and reinforcement history. In other words, these stimuli are functionally equivalent even though they look different. For example, if a learner is taught to respond with the label “dog” to pictures of dogs, a spoken word “dog,” and a dog-shaped toy, these varied items all call forth the same response despite their physical differences. That’s why the statement is true: the class is formed because of the shared response rather than any common physical property. The other ideas imply physical similarity (color or perceptual similarity), which isn’t what defines an arbitrary stimulus class.