In our two levels decision-making task, monkeys had to select two options in two consecutive steps, with the first choice determining the reward values at the second. Choosing the lowest value at the first level gives the possibility to choose the greatest value at the second level. In this design, the animal can’t make wrong answers, but his behavior could reflect different levels of engagement in the task and thus, different degrees of optimization. Looking at the entire recording session, optimality does not always imply aiming for the greatest values, but rather, as suggested by heuristics, ignoring some information in order to get an overall greater reward rate throughout the task. The levels of engagement in the task were categorized based on the animal’s behavior at both levels. The monkey can engage the task with cognitive control at only one of the two levels, both levels or not engage at all. Based on the literature, we formulated the hypothesis that the power of beta oscillations in the dorsolateral prefrontal cortex will be positively correlated with the level of engagement in the task and that higher cognitive control reflects optimality not through the most rational choice but on a sustained heuristic strategy. Preliminary results go toward a better decomposition of behavior for the interpretation of changes in the neural activity.