Each screen flashed before their eyes for one fifth of a second, so the students did not have time to count the dots before answering. Each series of tests consisted of dozens of screens; the researchers considered the most accurate answers across the two series to indicate a more highly developed approximate number system.

The researchers found that students with math learning disability (math scores at or below the 10th percentile) had the poorest ANS scores. Mazzocco said that this finding suggests that problems with the ANS underlie math difficulties for children in this group.

However, children in the 11th to 25th percentile, on average, were no more likely to have poor ANS scores than were children in higher percentiles, who had no mathematical difficulties. It seems likely, Mazzocco said, that math difficulties in this group stem from a cause or causes distinct from the ANS.

“Children with mathematical learning difficulties are often viewed as a uniform group of students, for whom a single type of special instruction or math curriculum is appropriate,” Mazzocco said. “Our findings suggest, however, that children have difficulty with math for different reasons.”

Approximately 10 percent of school-age children have persistent and significant difficulties with math, and many more fail to achieve basic levels of mathematics achievement, Mazzocco said.

“If you have a health problem, a physician will examine you to determine the details of your condition and then will recommend a treatment plan specific to your needs,” said Mazzocco. “In the same way, educators need to be able to determine the factors underlying math difficulties so that they can tailor instructional methods to individual students’ needs. A poor number sense seems to underlie math learning disability for many individuals, but it may not underlie poor math achievement for all students who struggle with math.”