Stimuli, settings, and activities only fit the definition of reinforcers if the behavior that immediately precedes the potential reinforcer increases in similar situations in the future; for example, a child who receives a cookie when he or she asks for one.If the frequency of "cookie-requesting behavior" increases, the cookie can be seen as reinforcing "cookie-requesting behavior".A primary reinforcer, sometimes called an unconditioned reinforcer, is a stimulus that does not require pairing with a different stimulus in order to function as a reinforcer and most likely has obtained this function through the evolution and its role in species' survival.Examples of primary reinforcers include food, water, and sex.In turn, the strict sense of "reinforcement" refers only to reward-based conditioning; the introduction of unpleasant factors and the removal or withholding of pleasant factors are instead referred to as "punishment," which when used in its strict sense thus stands in contradistinction to "reinforcement." Thus, "positive reinforcement" refers to the addition of a pleasant factor, "positive punishment" refers to the addition of an unpleasant factor, "negative reinforcement" refers to the removal or withholding of an unpleasant factor, and "negative punishment" refers to the removal or withholding of a pleasant factor.This usage is at odds with some non-technical usages of the four term combinations, especially in the case of the term "negative reinforcement," which is often used to denote what technical parlance would describe as "positive punishment" in that the non-technical usage interprets "reinforcement" as subsuming both reward and punishment and "negative" as referring to the responding operant's evaluation of the factor being introduced. Skinner was a well-known and influential researcher who articulated many of the theoretical constructs of reinforcement and behaviorism.
"Positive" actions are those that add a factor, be it pleasant or unpleasant, to the environment, whereas "negative" actions are those that remove or withhold from the environment a factor of either type.The memory-enhancing stimulus can also be one whose effects are directly rather than only indirectly emotional, as with the phenomenon of "flashbulb memory," in which an emotionally highly intense stimulus can incentivize memory of a set of a situation's circumstances well beyond the subset of those circumstances that caused the emotionally significant stimulus, as when people of appropriate age are able to remember where they were and what they were doing when they learned of the assassination of John F.Kennedy or of the September 11, 2001, terrorist attacks.By contrast, technical parlance would use the term "negative reinforcement" to describe encouragement of a given behavior by creating a scenario in which an unpleasant factor is or will be present but engaging in the behavior results in either escaping from that factor or preventing its occurrence, as in Martin Seligman's experiments involving dogs' learning processes regarding the avoidance of electric shock. Skinner defined reinforcers according to the change in response strength (response rate) rather than to more subjective criteria, such as what is pleasurable or valuable to someone.Accordingly, activities, foods or items considered pleasant or enjoyable may not necessarily be reinforcing (because they produce no increase in the response preceding them).