The essence of the decision-making mechanism of rational individuals in economics is to ensure the balance between benefits and costs. The benefit received from a decision is expected to be higher than its cost. It is so in cognitive activities. Any cognitive practice may require effort, expenses, and time-use to some extent. However, the actors do not always do all they can. A significant reason for not using cognitive abilities adequately in verbal, written, and visual information production is the individuals’ not wholly bearing the negative consequences of their cognitive actions. Such a cognitive attitude differs from similar notions of rational ignorance, rational inattention, and mental laziness. This paper introduces a new concept, cognitive negligence, that refers to the tendency of individuals to avoid the cost and maximize benefits in cognitive activities by making an implicit or explicit cost-benefit analysis. The paper presents why and how cognitive negligence emerges. It defines the factors affecting it, such as the position of the actor, perception of importance, context or type of activity, time of action, social distance, and the diversity of the audience. Its relationship with lying, distortion, and critical thinking is discussed. Finally, the consequences of cognitive negligence are evaluated.