Sam's son got into the habit of slapping him in the face when he would greet him. At first Sam would laugh and pretend to slowly chase him around the house until he finally caught him and tickled him, but he noticed his son started to slap other people. Realizing this was an issue he decided to stop reinforcing the slapping behavior all together. His son started to slap incessantly and attempted to run off. The slapping increased in frequency and intensity from what it was before Sam started his intervention. This increase in slapping is an example of what?