Memories of reinforcement events are quite salient, stimulus salience being among the factors that determine incremental growth of inhibition or excitation on a trial. When memories gain in excitatory or inhibitory strength, stimuli that co-occur with them do likewise, and excitatory or inhibitory gain in those other stimuli depends in part on salience. The incremental gain in excitatory or inhibitory growth depends on the discrepancy between what we call expectancy of reinforcement on a trial and the reinforcement outcome on that trial. It is not clear whether expectancy is determined by the excitation of the memory alone or whether that excitation summates with that acquired by other stimuli. In any event, when expectancy on a trial is equal to the reinforcement outcome on that trial, excitatory or inhibitory growth ceases. Inhibitory growth in extinction, which will be considered at greater length later, is usually limited in extinction because expected reinforcement usually rapidly reduces to zero or close to zero (see Capaldi et al., 2009). To summarize the later treatment of extinction: Successive nonreinforcements produce increasing stimulus change, enough to place the animal in an internal stimulus context that drastically reduces expectancy (see, e.g., Capaldi, 1967, 1994). According to this view, in extinction the CS remains excitatory but is only a part of a much larger no-excitatory context.