Value of knowing when reinforcement is due.

In 4 experiments concerning preference for knowing when reinforcement is to be delivered—although that information has no apparent instrumental value—pigeons chose between informative and noninformative stimulus sequences. Following an informative choice, the stimulus was correlated with the prevailing interval before reinforcement; following a noninformative choice, it was not. Strong preference for the informative sequence, regardless of the proportion of short vs. long reinforcement intervals, was unaffected by addition of a reliable cue at the moment of reinforcement. Cue strength of the various stimuli was assessed. A control experiment excluded explanations in terms of preference for unpredictable sequences, variety, or specific stimuli. The results are discussed in terms of secondary reinforcement.