We put more mental effort into a task if the reward is big According to a study, the amount of mental effort humans put into a certain task is usually influenced by the gains/ benefits they are going to get New Delhi: We invest mental effort in a task in response to what we stand to gain, and in response to how much the outcome hinges on our performance, research finds. For example, what makes a person decide to turn off the TV and switch on their brain to complete work for their job? We tend to assume that the amount of mental effort a person invests in a task is influenced by the reward they stand to gainâso in this case, the effort results in a paycheck, and successful efforts could result in ego-pumping praise from a supervisor, a bonus, a promotion, or perhaps even a new, higher-paying job.