Extinction and overexpectation are two paradigms by which a previously established association between a CS and US can be altered. Both mechanisms occur by a reward expectation that is higher than the delivered reward (or omission of reward) which consequentially decreases the expectation of an outcome, manifesting in a corresponding decrease in behavioural response. Both effects have been documented in both male and female rats. After undergoing an overexpectation or extinction design, it is possible to obtain a recovery in conditioned responding either by the passage of time (spontaneous recovery) or by a change in context upon test (renewal). Additionally, a recovery in responding has been found to occur following unsignalled presentations of the US after extinction training and prior to test (reinstatement). The presentation of the unsignalled US works to re-establish responding to the target cue post-extinction in the absence of any additional CS-US pairing. To date, this reinstatement effect had not been studied following overexpectation training. In the present thesis, we examined whether reinstatement can be obtained following overexpectation training in male and female rats. The results show some evidence for a reinstatement in behavioural responding, albeit weak, following overexpectation in male but not female rats. The present findings have implications for understanding the mechanisms by which reinstatement occurs.