A heterogeneous chain requires different responses for each link of the schedule. Dog trainers make use of heterogeneous chains when they teach complex behavioural sequences to their animals. In going for a walk, a seeing-eye dog stops at intersections, moves forward when the traffic is clear, pauses at a curb, avoids potholes, and finds the way home. Each of these different responses is occasioned by specific stimuli and results in conditioned reinforcement. See also chain schedule.