Prosocial motivation as cost-benefit decisionsIn everyday life, people help others, from assisting colleagues with a task, to holding doors for strangers. These types of actions have been called prosocial behaviors-actions that benefit others (1). These behaviors are found not only in humans but also in a wide range of species where individual actions increase the fitness of a group, facilitating social cohesion (2-4). In humans these behaviors are very versatile and vary between contexts and individuals. Characteristics of the beneficiary (e.g., family vs. strangers), of the agent (e.g., personality traits), and the context (e.g., type of benefit), all influence how willing people are to help others (4-9). Understanding how these characteristics modulate willingness to help is important to uncover why there is variability in prosocial behavior.Here, I propose that a group of prosocial behaviors could be conceptualized as goaldirected actions (10)-actions that benefit others at the agent's own cost. The agent needs to be incentivized by the social benefit to overcome the cost and perform the action. Thus, in this group of actions, the material and direct benefit of the action is not received by the agents themselves but by others. The probability of a prosocial action to occur will depend then, among other factors, on how costly and how beneficial the action is-e.g., high benefits for low costs would have a high probability for the prosocial action to occur and vice versa. Crucially, this cost-benefit process is highly subjective-e.g., some people could be highly sensitive to others' welfare, and be prosocial for little benefit regardless of the cost, while others could be very sensitive to the cost, refraining to act even if the cost is low, regardless of the social benefit. This framework can be conceptually and methodologically powerful when addressing prosocial motivation. First, it can account for different types of behaviors that, in appearance, might not seem necessarily related. For instance, effortful prosocial actions, where effort costs need to be overcome to benefit others; and harm aversion, where costs are incurred to decrease others' suffering, have been linked empirically under a cost-benefit framework (11). Thus, costs (e.g., effort, time, money, distress) and benefits (e.g., money, avoiding harm, food, emotional support) can vary across contexts, but the decisional process might share similar principles. Secondly, using computational models, this framework allows us to understand the mechanisms underlying prosocial behaviors across different contexts, while capturing the idiosyncratic cost-benefit evaluations performed by individuals (10, 12, 13). Finally, costs and benefits can be manipulated and measured separately in experimental paradigms, accounting for individual variability in the sensitivities that people have to each element of the decision (10). Considering all of the above, in the following I will describe how a costbenefit framework could be useful to address inter-individual and int...