ON THE SURPRISINGLY PROLONGED DEVELOPMENTAL TRAJECTORY OF (CENTRAL) AUDITORY PROCESSING

Banai K.

University of Haifa, Israel.

Developmental gains in the ability to detect and discriminate fine acoustic differences between sounds are usually attributed to either sensory factors or to the ability to attend to the relevant auditory cue for the duration of the assessment. Here we show that depending on the task listeners are required to perform, frequency discrimination thresholds are either adult- like by 8 years of age (when measured with an oddball procedure in which listeners are asked to select the ‘odd-one-out’ among three alternatives) or still not adult- like by 14 years of age (when measured with a 2-interval-2-alternative-forced-choice identification procedure in which listeners are asked to determine which of 2 tones is higher). Because the stimuli used in both assessments were similar, sensory maturation seems an unlikely account for these findings. On the other hand, task related cognitive factors cannot account for the entire developmental difference between the oddball and identification procedures either, because in contrast to frequency discrimination, the ability to detect amplitude modulations (AM detection) is not adult like by 12 years of age even when assessed with an oddball procedure. To derive a measure of auditory attention during task performance, within listener performance consistency, determined as the standard deviation around the mean discrimination or detection threshold was analyzed. Contrary to expectation, this measure could not account for the developmental trajectory of either frequency discrimination as assessed with the identification procedure or of AM detection measured with the oddball procedure. These data imply that attentional factors alone are also not likely responsible to the prolonged development on these tasks. Therefore cognitive functions other than sensation and attention and which continue to develop during adolescence may be responsible for the development of auditory discrimination and should be taken into account in both research on and diagnosis of Auditory Processing Disorders.

E-mail: kbanai@research.haifa.ac.il