Nonsymbolic Comparison in Deaf Students: No Evidence for a Deficit in Numerosity Processing.

It is commonly found that deaf and hard of hearing (DHH) students experience delayed mathematical achievement. The present study used two nonsymbolic comparison tasks to explore the basic numerical skills of DHH students. Nine prelocutive DHH students with cochlear implants and nine hearing students, matched on nonverbal IQ, visual short-term memory, and verbal comprehension, were recruited. The participants performed two different collection comparison tasks with different ratios and under different perceptual conditions. Analyses by task showed similar response times, accuracy, and ratio effects for both groups on the Low Perceptual Condition task, a finding suggesting that the two groups accessed similar representations of quantity. Differences in performance on the simpler High Perceptual Condition task, on which the DHH group showed slower response times, probably were strategic in origin. The results suggest that DHH students have no deficits in basic numerical skills.

Is place-value processing in four-digit numbers fully automatic? Yes, but not always.

Knowing the place-value of digits in multi-digit numbers allows us to identify, understand and distinguish between numbers with the same digits (e.g., 1492 vs. 1942). Research using the size congruency task has shown that the place-value in a string of three zeros and a non-zero digit (e.g., 0090) is processed automatically. In the present study, we explored whether place-value is also automatically activated when more complex numbers (e.g., 2795) are presented. Twenty-five participants were exposed to pairs of four-digit numbers that differed regarding the position of some digits and their physical size. Participants had to decide which of the two numbers was presented in a larger font size. In the congruent condition, the number shown in a bigger font size was numerically larger. In the incongruent condition, the number shown in a smaller font size was numerically larger. Two types of numbers were employed: numbers composed of three zeros and one non-zero digit (e.g., 0040-0400) and numbers composed of four non-zero digits (e.g., 2795-2759). Results showed larger congruency effects in more distant pairs in both type of numbers. Interestingly, this effect was considerably stronger in the strings composed of zeros. These results indicate that place-value coding is partially automatic, as it depends on the perceptual and numerical properties of the numbers to be processed.

Quantity processing in deaf and hard of hearing children: evidence from symbolic and nonsymbolic comparison tasks.

Deaf children usually achieve lower scores on numerical tasks than normally hearing peers. Explanations for mathematical disabilities in hearing children are based on quantity representation deficits (Geary, 1994) or on deficits in accessing these representations (Rousselle & Noël, 2008). The present study aimed to verify, by means of symbolic (Arabic digits) and nonsymbolic (dot constellations and hands) magnitude comparison tasks, whether deaf children show deficits in representations or in accessing numerical representations. The study participants were 10 prelocutive deaf children and 10 normally hearing children. Numerical distance and magnitude were manipulated. Response time (RT) analysis showed similar magnitude and distance effects in both groups on the 3 tasks. However, slower RTs were observed among the deaf participants on the symbolic task alone. These results suggest that although both groups' quantity representations were similar, the deaf group experienced a delay in accessing representations from symbolic codes.