Observing behavior: Redundant stimuli and time since information

Pigeons were allowed to observe a stimulus signaling food (S+) by pecking one side key of a three-key chamber, or a stimulus signaling extinction (S?) by pecking the opposite side key. Components were 30 sec long and separated by 3-sec blackouts (after extinction periods) or 3-sec access to an illuminated food hopper (terminating food periods). Pigeons came to peck the S+ key almost exclusively. When food and extinction periods were presented in random order, the S+ key was pecked in nearly every component. But when the components alternated in abab fashion, the probability of an S+ keypeck during extinction decreased (after 3-sec access to food) while remaining high in food components (after 3-sec blackout). This suggested the development of trace stimulus control by the stimuli separating the components and that redundant stimuli would maintain observing when they signaled food. Results were discussed in terms of traditional notions of conditioned reinforcement and were not seen as supporting information theory explanations of observing behavior.