Semper Fi“Always faithful” is a message not only for members of the United States Marines but also for anyone involved in changing behavior. The core principle of behavior change is reinforcement, and the core principle of reinforcement is consistency between the occurrence of the targeted behavior and the consequence that follows. This does not mean that every instance of the target behavior should be followed by a reinforcer, but when reinforcers occur they are most effective when they immediately follow the targeted response. When this happens, the reinforcement procedure is said to have good fidelity or integrity. ​

A simple experiment with pigeons illustrates the point. When reinforcers are scheduled following the first response after varying periods of time between the reinforcers, responding is very regular and of moderate rate. For a pigeon pecking a plastic disk or key, this can be anywhere from 25 to 150 pecks a minute (yep, a minute). In this case the schedule has high fidelity in that when reinforcers (3 seconds of access to food) occur, they always do so immediately following a response. Now, let’s change the experiment so that over several conditions the fidelity of the schedule is varied such that different percentages of the total number of reinforcers immediately follow the response, but the others occur independently of the pigeon’s key pecks. In the latter case, it doesn’t matter whether the pigeon is pecking or not, the food is delivered. As we decrease the percentage of reinforcers that occur immediately after the response, and as a result simultaneously increase the number of reinforcers that are response independent, fidelity decreases. The effect of this decrease in fidelity is a corresponding decrease in the rate of key pecking. That is, as we decrease fidelity, we decrease the effectiveness of the schedule, or program, in controlling behavior.

Teachers of all sorts (not just school teachers, but anyone having oversight responsibility for learning by other people) often are reminded of the need for consistency in managing their charges. The behavior of the elementary school student and the employee are both determined by the fidelity with which the available rewards are made contingent on targeted behavior, behavior that has been selected because of its potential value to either the individual or the organization, or both. If only some of the available rewards follow the target behavior and others occur independently of that behavior, the same relation shown with pigeons in the previous example will be the result. Successes and failures of fidelity predict precisely how well the new plan will accomplish its goals. It therefore is critical in implementing new behavioral technology that procedures are in place to ensure that the technology is implemented as it was developed and that implementers be monitored and given feedback on how well they are implementing the prescribed programs.

Exactly the same is true of self-management programs. Want to lose weight? The secret is a simple one: follow the program, for if the poorer the fidelity the poorer will be the outcome in terms of weight loss.

All of this suggests that whenever we are planning to start behavior change programs in our personal, family or work lives it is essential to follow the guiding rule of those few good men: “Semper Fi.” 


Posted by Andy Lattal, Ph.D.

Dr. Andy Lattal is the Centennial Professor of Psychology at West Virginia University (WVU). Lattal has authored over 150 research articles and chapters on conceptual, experimental, and applied topics in behavior analysis and edited seven books and journal special issues, including APA’s memorial tribute to B. F. Skinner.