The nonintentional processing of Arabic numbers in children.

This paper aims at determining when magnitude is automatically activated from Arabic digits in children and whether this automatic activation depends on the number size of the stimuli considered. Second, third, and fourth graders performed a physical Stroop task in which pairs of single- and two-digit Arabic numerals in a ratio 1:2 or 2:3 were used. In addition, the speed of perceptual and semantic information was balanced: Instead of presenting the two members of each pair directly with a physical size difference, they first appeared in the same intermediate physical size, the perceptual difference occurring only after some time. The results indicated a significant effect of congruity at all grades, with faster reaction times and lower error rates for congruent trials than for incongruent trials, for both one- and two-digit numerals. Furthermore, this congruity effect was affected by the ratio of the numbers in the pairs. Only pairs of ratio 1:2 were affected by this congruity effect. These findings strongly support the fact that children as young as 7 years old can automatically access the magnitude information of one- as well as two-digit Arabic numerals.