Approach Gradient

The approach gradient is a concept in Behaviorism that describes the change in intensity or drive as an organism approaches a desired or pleasant stimulus such as food. This is the opposing concept of avoidance gradient which describes the change in intensity or strength of an organism's drive and response as it nears a fearful or unpleasant stimulus (such as an electric shock).

For example, the approach gradient of a mouse could be measured by it's heart rate and level of arousal as it nears a piece of food in a previously run maze. The mouse knows it is nearing food and is essentially getting more exited about it as it approaches.