Figure 1

The structure and timing of one trial. Left, timing of one trial in the comparison task block. a: The first number. b: The second number. In the comparison task, subjects were asked to compare b with a, and decide whether b was bigger or not by pressing “p” or “q”, respectively. Right, timing of one trial in the calculation task. c: The solution. d and e: The first operand and the second operand of a multiplication problem, respectively. In the calculation task, subjects were asked to decide whether the result of d × e was greater or not by pressing “p” or “q”, respectively. Then, they indicated the method they used to solve the problem by pressing “1” (approximate calculation) or “2” (exact calculation), respectively.