Negative reinforcement

Removing something the animal will work to avoid to strengthen (increase the frequency of) a behavior. Heeling is traditionally taught through R-. The dog receives a “correction” when he walks anywhere except in heel position. Walking in heel position increases because that is the only “safe” place—because the threat of correction is removed by walking there. The key to R- is that an aversive must first be applied or threatened in order for it to be removed.