What is the relation between cognition and emotion? Three kinds of answers can be discerned from the educational and psychological literature. First, some emotional reactions can be elicited without the intervention of cognition (the opposite has not yet been documented). Second, cognition is a cause of emotion. Thus, many emotional reactions and modulations are contingent upon or influenced by the individual's (cognitive) appraisal of the stimuli coming from his/her body, mind, and environment. There is also a robust relationship between the individual's understanding of emotion (including of their regulation) and his/her emotional well-being. Third, emotion is a cause of cognition. Thus, emotional arousal and valence have an influence on, for example, memory, attention, and creativity. This impact is neither linear nor symmetrical: Emotional arousal has to be neither too low nor too high to have an optimum impact and the impact of negative emotions seems clearer than the impact of positive emotions. In this article, we claim that the identification of causal relations between cognition and emotion may to a great extent depend on the moment one takes a snapshot in the flow of the individual's subjective experience. We also claim that, as a function of the situation (context, circumstances, etc.) and the individual (personality level of development, etc.), either cognition or emotion may be dominating the individual's mental functioning and, further, that the absence of this circularity would be dysfunctional for the individual. © 2010 Elsevier Ltd. All rights reserved.