In this paper, using data provided by an empirical study of students in a high school science course, we discuss
key variables in the interaction between System 1 (S1) (intuitive and unconscious processes) and System 2
(S2) (analytical and conscious processes) in mathematical reasoning. These variables are: beliefs about oneself
and about mathematics; cognitive reflection understood as a self-regulatory skill; working memory; and the
evaluation of the deductive and probabilistic reasoning of students. The results confirm the interaction between
these variables and their predictive power on performance in mathematics. The study also adds novel considerations
related to the function and interaction of cognitive and metacognitive components involved inmathematical
performance.