Poster C111, Sunday, March 25, 1:00-3:00 pm, Exhibit Hall C
Individual differences in IPS and PFC function predict fraction knowledge in children
Priya B. Kalra1, John V. Binzak1, Yunji Park1, Elizabeth Y. Toomarian1, Percival G. Matthews1, Edward M. Hubbard1; 1University of Wisconsin--Madison
We have recently argued that humans have a ratio processing system (RPS) adapted to perceiving non-symbolic ratios (e.g. the ratio of two lines; Lewis, Matthews & Hubbard, 2015), that may support understanding of symbolic fractions (e.g. ¾). Consistent with this model, RPS sensitivity correlated with a pencil-and-paper measure of fractions knowledge (the Fractions Knowledge Assessment: FKA), in college students, even controlling for other skills (Matthews, Lewis & Hubbard, 2016). Here, we further test the RPS hypothesis by measuring brain-behavior correlations in 2nd and 5th grade children. Children took part in a battery of behavioral tasks, including an age-appropriate FKA and an fMRI fraction magnitude judgment task with three stimulus types: symbolic ratios, non-symbolic ratios, or mixed pairs. This task has consistently revealed a neural distance effect (NDE) localized to bilateral IPS and PFC (Binzak et al., 2017): comparison of close ratios (e.g., 5/6 vs. 4/7) leads to greater activation than comparison of far ratios (e.g., 1/8 vs 7/9). For 2nd graders, the NDE across all stimulus types was positively correlated with FKA scores in bilateral IPS (larger in the right) and right PFC. In contrast, 5th graders’ FKA scores were positively correlated with the NDE only for non-symbolic ratios in a left hemisphere parieto-frontal network. Furthermore, the NDE for symbolic fractions was negatively correlated with FKA scores in bilateral IPS. These findings suggest that differences in IPS and PFC function support individual differences in fractions understanding, and that early math instruction may lead to progressive left lateralization for ratio processing.
Topic Area: THINKING: Reasoning