As illustrated in this case, Mrs. Sims uses star stickers as a concrete reinforcer in an effort to promote positive responses from her students. On one occasion, Hing-su and Ryan are at the whiteboard solving a math problem. Hing-su answers the question correctly and as a result, he received both verbal affirmation (social reinforcer) and a purple star (positive reinforcer). Unfortunately, Ryan did not receive a star because his answer was incorrect (negative reinforcer). However, Mrs. Sims asked Teresa to solve the problem, which she did correctly and she received the star. This type of reinforcement seems ineffective and socially unsound. Since Ryan answered the problem incorrectly, he most likely felt embarrassed in front of his peers and
