APA Dictionary of Psychology

a schedule of reinforcement for a single response in which two or more schedule requirements must be completed in sequence before reinforcement occurs and no stimulus change accompanies completion of each requirement. For example, in a tandem, fixed-interval 1-minute, fixed-ratio 10 schedule, the first response after 1 minute would initiate the fixed-ratio schedule, and the 10th response would result in reinforcement. Also called tandem schedule of reinforcement. Compare chained schedule.