Fig. 1: Sexual dimorphisms in motivation: female mice work harder for nondrug rewards.

a Schematic of sucrose self-administration in male and female mice. Mice went through a series of different reinforcement schedules to determine how their behavior changed with changing contingencies. b Average sucrose consumption under a fixed ratio 1 (FR1) schedule of reinforcement (1 response = 1 sucrose delivery) between male and female mice in a sated condition, normalized to body weight. Females consume more sucrose than males. c Average responses for sucrose under variable ratio 3 (VR3) and VR5 schedules of reinforcement between male and female mice, normalized to baseline (responses during first day of VR3). d Average change in sucrose consumption in mg from VR3 to VR5 between male and female mice, normalized to body weight. Female mice increase consumption compared to male mice when the required effort to obtain each reinforcer was increased. e Schematic of within-session threshold procedure in male and female rats. Representative demand curves for sucrose of f male and g female rats during the within-session threshold procedure. h Economic analysis: standardized P_max values—the maximal price an animal is willing to pay in effort to obtain sucrose—for male and female rats during the within-session threshold procedure. Standardized P_max is calculated as P_max × Q₀ and controls for potential differences in consumption between groups. We did not find differences in sucrose consumption between males and females under these conditions (Supplementary Fig. 1). Standardized P_max for sucrose is higher in females compared to males indicating that they are more motivated to work to obtain sucrose as effort requirements are increased. All data reported as mean ± SEM. *p < 0.05. Diagrams created with biorender.com.