Mr. Romley notices a group of students in his fifth-grade class who sit together and do logic puzzles during free-learning time in the classroom. He had been planning to distribute the puzzles as part of a lesson, but the group found them in a cupboard and took to working on them together. Mr. Romley is delighted the group uses and enjoys them. He praises them and starts giving them stickers for completed puzzles. After a while, Mr. Romley notices the group spends less time on puzzles than on counting and comparing stickers, that there are frequent arguments about who has finished first, and that the less-competitive children in the group have drifted off to do something else. According to theories of motivation and self-efficacy, what factors and interactions contributed to the students' behavior–positive and negative, before and after Mr. Romley introduced the stickers?