Continuum of impulsiveness caused by auditory masking

Impulsivity is a hallmark of attention deficit/hyperactivity disorder (ADHD). Various auditory masking procedures can quantify the impulsivity caused by distracting background sounds. This study compares the impulsiveness and distraction caused by informational masking (unpredictable tones) with previously published data on central masking (contralateral noise) in children with and without ADHD.

Twenty-six normal and 14 children diagnosed as having ADHD (combined type), all between the ages of 7 and 13, indicated whether they heard a 512-ms, 500-Hz pure tone in a single-interval task under conditions of informational masking and in quiet. The masker consisted of 10 randomly selected frequencies between 1,000 and 2,500 Hz presented simultaneously at an overall level of 60 dB SPL. A maximum-likelihood method estimated thresholds and false alarm rates.

There were no differences due to ADHD in thresholds or false alarm rates either with informational masking or in quiet. With informational masking, normal children had high false alarm rates, similar to those from children with ADHD under central masking. With informational masking, all children tended to say a stimulus was present when it was not.

All children behave impulsively under some conditions. Pediatric patients with attention disorders can thus be reassured that impulsiveness with unpredictable background sounds is normal, to some extent. Response biases of children with ADHD may only diverge from normal in situations where distracting external stimuli have an intermediate level of predictability. A previous study showed that with central masking, children with ADHD are more impulsive than normal. There appears to be a limit to the uncertainty in auditory masking that can be tolerated by children. Children with ADHD become impulsive at lower levels of uncertainty than normal. Increasing the predictability of distracting background sounds may thus improve the performance of children with ADHD. Informational masking may, for normal listeners, mimic something of what it is like to have an attention deficit. ADHD can be profitably studied with auditory tasks.