Behavioral flexibility is an adaptive process where one alters behavior due to a change in the internal or external environment. Prior research in the field shows that both the dorsolateral striatum (DLS) and dorsomedial striatum (DMS) contribute to the regulation of behavioral flexibility in instrumental conditioning. I begin in Chapter 1 by presenting background literature on behavioral flexibility, comparing instrumental and Pavlovian paradigms, and considering sex differences in either context. In Chapter 2, I focus on how male and female Long Evans rats differ in the expression of a Pavlovian conditioned response and sensitivity to outcome devaluation and how DMS cannabinoid-1 receptors (CB1Rs) mediate these processes. I find that females show more lever-directed behavior and are insensitive to outcome devaluation. I also find that DMS CB1Rs are required for the devaluation sensitivity of males. In Chapter 3, I use slice electrophysiology to assess whether DMS inhibitory tone at baseline differs between males and females and how CB1R activation affects inhibitory synaptic transmission. I find that cells recorded from male rats show reduced frequency of inhibitory events and that CB1R activation reduces inhibitory tone in both males and females. In Chapter 4, I investigate the relationship between social reward and sign-tracking. I find that sign-tracking behavior persists under extinction and in the presence of an alternative reward choice. Collectively, this research establishes a role for DMS CB1R in Pavlovian outcome devaluation and supports previously established sex differences in behavioral flexibility.