Women compared with men work harder for small rewards

Abstract

In cost-benefit decision-making, women and men often show different trade-offs. However, surprisingly little is known about sex differences in instrumental tasks, where physical effort is exerted to gain rewards. To this end, we tested 81 individuals (47 women) with an effort allocation task, where participants had to repeatedly press a button to collect food and money tokens. We analyzed the motivational phases of invigoration and effort maintenance with varying reward magnitude, difficulty, and reward type. Whereas women and men did not differ in invigoration, we found that women showed higher effort maintenance as well as higher subjective wanting and exertion ratings for small rewards compared with men. Notably, men increased their effort more than women for higher rewards to match women's levels of performance. Crucially, we found no sex differences depending on reward type or difficulty, indicating that sex differences were specific to the encoding of the magnitude of benefits, not costs. To summarize, women exerted higher physical effort for small rewards, which corresponded with an elevated subjective value in women compared with men. Therefore, sex differences in perceived reward magnitude may contribute to differential behavioral preferences highlighting the potential of cost-benefit decision-making to provide insights about potential mechanisms.

Figure 1

Women and men differ in effort maintenance, depending on reward magnitude. (a) Trial-based data showing that women had overall higher effort maintenance than men (main effect of sex, p = 0.003). Women generally outperformed men for small rewards, but when more reward was at stake, men adjusted their effort to match women’s performance (interaction sex × reward magnitude, p = 0.022). (b,c) show empirical Bayes estimates (EB).

Figure 2

Women and men differed in subjective ratings of wanting and exertion. (a) Both women and men had higher wanting ratings for higher rewards than smaller rewards, p < 0.001, but women wanted smaller rewards more than men did, p = 0.003. (b) Both women and men reported to put in more effort for higher rewards than for smaller rewards, p < 0.001, and women reported more exertion for smaller rewards than men, p = 0.004.

Figure 3

Schematic depiction of the effort allocation task. First, fixation cross is shown, followed by the reward cue. To earn reward, participants have to keep a ball above the red line by repeatedly pressing a button with their right index finger. Reward magnitude (low vs. high), difficulty (easy vs. hard), and reward type (food vs. money) were manipulated as task conditions. The lower left graph shows a representative time series of a high-difficulty trial, depicting effort output as button press rate, BPR, in % relative to the maximum frequency of the participant. Invigoration slopes captured how quickly participants reach effortful behavior during a trial to collect the reward. Effort maintenance relates to the average relative frequency on the trial. Figure taken from under CC BY license (https://creativecommons.org/licenses/by/4.0/); no changes have been made to the figure.