Participants with lower intellectual ability had more difficulty identifying a single speaker in noisy environments despite normal hearing, according to a recent study.

Lower intellectual ability was associated with poorer auditory multitalker speech perception in neurodivergent participants with clinically normal hearing, according to researchers who identified a strong negative correlation between cognitive scores and the ability to identify a target talker amid competing voices. This relationship held across autism, fetal alcohol spectrum disorder, and comparison groups, highlighting that general intellectual ability influenced performance under complex acoustic conditions regardless of diagnosis.

The study, published in PLOS One, included 12 participants with autism, 10 with FASD, and 27 age- and sex-matched comparison participants, all with clinically normal hearing. All participants passed audiometric and distortion product otoacoustic emission screening to confirm typical peripheral hearing. Intellectual ability was measured using the Weschler Abbreviated Scale of Intelligence – Second Edition. Patients then completed an adaptive multitalker speech perception task using Coordinate Response Measure stimuli. Three simultaneous sentences were presented, with the target talker positioned at zero degrees azimuth and two maskers at plus or minus 45 degrees. A one-up-one-down adaptive method varied masker intensity to calculate the target-to-masker ratio corresponding to 50% accuracy. More positive ratios indicated poorer performance, reflecting a need for the target to be louder than the competing talkers.

Across the full sample, lower Full Scale IQ scores were associated with higher thresholds, and this relationship persisted within each diagnostic group. Participants with autism and fetal alcohol spectrum disorder (FASD) generally required more favorable listening conditions to accurately identify the target talker, whereas many comparison patients succeeded even when maskers were louder. Secondary analyses showed correlations between speech perception thresholds and both verbal and nonverbal abilities.

Study limitations included relatively small sample sizes in the autism and FASD groups, which reduced the ability to assess differences between groups. They also acknowledged that including participants with attention-deficit/hyperactivity disorder could have introduced additional variability, although analyses did not show an association between attention-deficit/hyperactivity disorder status and task outcomes. In addition, the researchers noted that the laboratory task simulated a multitalker situation but did not include the multisensory and interactive elements that occur in everyday listening environments.

“This demonstrates that deficits in intellectual ability, despite intact peripheral encoding of sound, are associated with difficulty listening under complex conditions for individuals with autism and fetal alcohol spectrum disorder,” noted lead author Bonnie K. Lau  of the Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, and the Department of Otolaryngology – Head and Neck Surgery, University of Washington, Seattle, and colleagues.

The researchers reported no competing interests.

Source: PLOS One