LOS ANGELES, Nov. 25 (UPI) -- Dyslexia symptoms, including trouble reading and spelling, may be at least partly due to difficulty blocking out background noise, U.S. researchers say.

Rachel Beattie of the University of Southern California in Los Angeles said dyslexia affects as many as 17.5 percent of the U.S. population, but its cause remains somewhat unknown.


The study, involving 37 undergraduate students, found poor readers performed significantly worse than the control group only when there were high levels of background noise.

However, the two groups performed comparably at the prescribed task when there was no background noise and when the stimulus was varied, either to a large or small degree.

"These findings support a relatively new theory, namely that dyslexic individuals do not completely filter out irrelevant information when attending to letters and sounds," Beattie and study co-authors said in a statement. "The external noise exclusion deficit could lead to the creation of inaccurate representations of words and phonemes and ultimately, to the characteristic reading and phonological awareness impairments observed in dyslexia."

The findings were published online in the journal PLoS ONE.