Final answer:
It is false that what someone says they want is the best predictor of reinforcer effectiveness. Actual effectiveness is measured by how it affects behavior, and factors like immediacy, size, and contingency must be considered.
Step-by-step explanation:
The statement that what someone says they want is the best predictor of reinforcer effectiveness is false. In behavioral psychology, reinforcer effectiveness is not solely determined by self-report but also by direct observation of behavior change.
While self-reported preferences can provide insights into potential reinforcers, the actual effectiveness of a reinforcer is empirically tested through its impact on the frequency of the target behavior.
Various factors such as the immediacy, size, and contingency of the reinforcer also play critical roles in determining reinforcement effectiveness. Hence, a rigorous assessment of how a reinforcer affects behavior is necessary to ascertain its effectiveness, rather than relying solely on an individual's verbal expression of desire.