The differential effects of the amount of training on sensitivity of distinct actions to reward devaluation

Shifting between goal-directed and habitual behaviors is essential for daily functioning. An inability to do so is associated with various clinical conditions, such as obsessive–compulsive disorder (OCD). Here we developed a new behavioral model in mice allowing us to produce and examine the development of different behaviors under goal-directed or habitual control. By using overtraining of instrumental associations between two levers and two rewards, and later devaluating one of the rewards, we differentiate and explore the motivational control of behaviors within the task which consequentially promotes what seems like excessive irrational behavior. Using our model, we found that the ability of instrumental behavior, to adapt to a change in the value of a known reward, is a function of practice. Once an instrumental action was practiced extensively it becomes habitual and, thus, under S–R control and could not be amended, not even when resulting in a noxious outcome. However, direct consummatory or Pavlovian actions, such as licking or checking, responds immediately to the change in value. This imbalance could render an instrumental behavior excessive and unresponsive to changes in outcome while the direct change in consumption implies that the change was in fact registered. This could suggest a system that, when out of balance, can create excessive behaviors, not adapting to an acknowledged change.