Comparing the magnitude of two fractions with common components : which representations are used by 10- and 12-year-old children ?

Meert, Gaëlle [UCL] Grégoire, Jacques [UCL] Noël, Marie-Pascale [UCL]

This study tested whether 10- and 12-year-old children who can correctly compare the magnitudes of fractions with common components access the magnitudes of the whole fractions, rather than compare the magnitudes of their components. Moreover, we tested with a priming paradigm whether the magnitude of the denominators interferes with the processing of the fraction magnitude and whether inhibition controls this interference. Response times to fractions were predicted by the numerical distance between the whole fractions, suggesting an access to their magnitude. A negative priming effect was showed for the comparison of natural numbers primed by fractions with common numerators. This effect suggests an inhibition of the selection of the larger denominator and then the interference of the magnitude of the denominators with the selection of the larger fraction. In conclusion, children who can correctly compare fractions with common components can access the magnitude of the whole fractions, but remain sensitive to the interference of the relative magnitude of the denominators. This study highlights that beyond the interference of natural number knowledge at the conceptual level (called the whole number bias by Ni & Zhou, 2005), children have to manage the interference of the magnitude of the denominators (Stroop-like effect).