Experimental control is essential in operant conditioning. Without baseline measures, such as the operant level, it is difficult to draw conclusions about the reasons for any observed changes in operant response rates.
In the yoked control procedure, the rate of responding by an experimental subject is compared to that by a control subject; the latter is yoked to the former in terms of the receipt of reinforcement (or punishment). This comparison helps to confirm that changes in operant responding by the experimental subject are due to the contingencies of reinforcement between its behavior and its consequences; otherwise, the two subjects receive reinforcers (or punishers) at the same time.
For example, parents often give their child a treat as a reinforcer for good grades. Frequently, if the child has a sibling, parents will give the sibling a gift as well so that child will not feel ignored. The gift is not dependent on any previous behavior of the sibling.