Sharpening, focusing, and developing: A study of change in nonsymbolic number comparison skills and math achievement in 1st grade.

Children's ability to discriminate nonsymbolic number (e.g., the number of items in a set) is a commonly studied predictor of later math skills. Number discrimination improves throughout development, but what drives this improvement is unclear. Competing theories suggest that it may be due to a sharpening numerical representation or an improved ability to pay attention to number and filter out non-numerical information. We investigate this issue by studying change in children's performance (N = 65) on a nonsymbolic number comparison task, where children decide which of two dot arrays has more dots, from the middle to the end of 1st grade (mean age at time 1 = 6.85 years old). In this task, visual properties of the dot arrays such as surface area are either congruent (the more numerous array has more surface area) or incongruent. Children rely more on executive functions during incongruent trials, so improvements in each congruency condition provide information about the underlying cognitive mechanisms. We found that accuracy rates increased similarly for both conditions, indicating a sharpening sense of numerical magnitude, not simply improved attention to the numerical task dimension. Symbolic number skills predicted change in congruent trials, but executive function did not predict change in either condition. No factor predicted change in math achievement. Together, these findings suggest that nonsymbolic number processing undergoes development related to existing symbolic number skills, development that appears not to be driving math gains during this period. Children's ability to discriminate nonsymbolic number improves throughout development. Competing theories suggest improvement due to sharpening magnitude representations or changes in attention and inhibition. The current study investigates change in nonsymbolic number comparison performance during first grade and whether symbolic number skills, math skills, or executive function predict change. Children's performance increased across visual control conditions (i.e., congruent or incongruent with number) suggesting an overall sharpening of number processing. Symbolic number skills predicted change in nonsymbolic number comparison performance.

A direct comparison of exogenous and endogenous inhibition of return and selective attention mechanisms in the somatosensory system.

The interaction of excitation and inhibition in responses due to attentional mechanisms in the visual system has been investigated. The studies reported herein use the tactile system of humans to test a specific hypothesis about the processes of attention that have never been directly addressed. Both exogenous and endogenous Inhibition of Return (IOR) reaction-time paradigms with a 100 Hz, 35 microm of peak displacement amplitude were used. In these experiments multiple Stimulus Onset Asynchronies were tested which made it difficult for subjects to learn timing patterns. We tested whether a detection time to a target which is to be attended to is a composite of at least two underlying mechanisms. These mechanisms were explored using exogenous and endogenous IOR experiments. It is hypothesized that these mechanisms work in a push-pull fashion: one deploying attention when new events occur, and the other withdrawing attention ("Disengagement") after it has been deployed. Based on the results, a new hypothesis is proposed stating that one form of attention (selective attention) competes with IOR in determining the time taken to detect a target in the tactile system.