Grandma’s Law: What is it (really)?

How many times have we heard or perhaps even said something similar to the following: “Eat all of your vegetables and then you can have some ice cream.” This basic notion of doing something less desirable for the opportunity to do something more desirable is commonly known as Grandma’s Law. In the field of ABA this “law” is what we know as The Premack Principle.

The scientific gist of this principle is as follows:  Any behavior that is more likely to occur in a free choice situation can be used to reinforce any behavior that occurs less likely in a free choice situation. Or to put it simply, “clean your room (low-frequency response) and then you can play video games (high-frequency response.) When the high-frequency response is made contingent upon the occurrence of the low-frequency response, it then becomes a reinforcer for the low-frequency response. In this case, the video game will reinforce the behavior of cleaning the room. Here the reinforcer is pretty easy to pinpoint. However, according to the “law” it can reinforce many behaviors that we normally would not think of.

  • Example: When observed and given free choice to do as she wished, Sally’s most frequent behavior was computer play. At dinner she ate some of her vegetables, but not all of them. Without help or reminders, Sally did not do any of her homework.
  • Most likely to occur = computer;
  • Somewhat likely to occur = eating vegetables at dinner;
  • Least likely to occur = homework.

According to the Premack Principle, anything above the target behavior can and will reinforce it. So yes, even eating vegetables would reinforce Sally for doing her homework, and playing on the computer would reinforce her for eating her vegetables.

For ages and ages the idea of “this before that” has been utilized in households everywhere, but how does this principle benefit the field of ABA and the clients that it serves? First, if reinforcers have been difficult to identify, this gives therapists a new perspective and the ability to identify properties of the free choice environment that are reinforcing. Secondly, once reinforcers have been established we can move past the starting line and begin to shape, increase, or acquire the skills necessary to promote effective behavior change for our clients.