An operant (learned) behavior contingency in which a behavior is emitted, a stimulus is added to the environment, and as a result, the behavior is more likely to happen in the future. Positive is used to mean adding” something when the behavior occurs (such as giving a child a sticker when they clean their room) and reinforcement refers to the increased probability of that behavior happening again in the future (the kid cleans their room more often as a result of the added sticker).
“