Behavior Modifier was the name of a chip which Maggie Walsh implanted in Riley Finn, planning on using it during the final stage of 314 Project, which was intended to control his motor functions. Adam activated it in order to pacify Riley while Adam's plans came into the final stage.
Unlike the Behavior Modification Circuitry, this chip was tied directly into the central nervous system through the thoracic nerve instead of being implanted in the brain. Another difference is that this device did not work by causing pain, but by taking control of the victim's body, which was placed under the control of whoever controlled the chip.
As the creation of a behaviorist psychologist, the chip is intended to control observable behavior (actions) and not will, thoughts or desires, which are outside the field of behaviorism.