Fig. 1. Behavioral task and hypothesis.

(A) Choose phase of the CAST. In each CAST trial, participants were asked to choose between easy (i.e., low effort) choice cards, which always offered 2 cents, and hard (i.e., high effort) choice cards, which offered one of five possible reward amounts (2, 3, 4, 5, and 6 cents). The domain (either math or word) of the choice cards was kept the same within a trial. (B) Four example problems in the solve phase of the CAST. Participants were asked to fill the blue square to make a correct equation (math) or an English word by selecting one of three options below. In word problems, “~” is used in place of some characters to make problems harder. The problems were sorted by seven difficulty levels through a validation study (see the Supplementary Materials). Word answers: PL[A]N, EX[A]MINED. Math answers: 30[8], 2[5]84. (C) Expected reward and optimal decision-making as a function of the reward offered in the hard option (the horizontal axis). The horizontal dashed line represents the expected reward (the left vertical axis) of the easy option given the expected accuracy of 95%, and the black open circles represent the expected reward of the hard options, given the expected accuracy of 70%. The blue filled circles indicate the optimal choice probability of the hard options in each reward condition to maximize monetary reward based on expected reward values. (D) Math-specific effort avoidance hypothesis. The hard choice probability (HCP; the vertical axis) was defined by averaging the individual HCPs in the 4-, 5-, and 6-cent conditions (C). We predicted that math anxiety would be negatively correlated with the math HCP (red thick line) but not with word HCP (black line).