Mr. Goldstein gives his students points, usable for extra free time, when they raise their hands and wait to be called on. He discovers that more students raise their hands and fewer students blurt out answers when he awards points than when he does not. What does this finding seem to show?
1) A functional relation between points and hand-raising
2) Punishment for raising hands
3) Points serving as a motivating operation for hand-raising
4) Points exerting stimulus control over blurting out answers