To identify the factors that may underlie the deficits in children with listening difficulties, despite normal pure-tone audiograms. These children may have auditory processing disorder (APD), but there is no universally agreed consensus as to what constitutes APD. The authors therefore refer to these children as children with suspected APD (susAPD) and aim to clarify the role of attention, cognition, memory, sensorimotor processing speed, speech, and nonspeech auditory processing in susAPD. It was expected that a factor analysis would show how nonauditory and supramodal factors relate to auditory behavioral measures in such children with susAPD. This would facilitate greater understanding of the nature of listening difficulties, thus further helping with characterizing APD and designing multimodal test batteries to diagnose APD.
Factor analysis of outcomes from 110 children (68 male, 42 female; aged 6 to 11 years) with susAPD on a widely used clinical test battery (SCAN-C) and a research test battery (MRC Institute of Hearing Research Multi-center Auditory Processing “IMAP”), that have age-based normative data. The IMAP included backward masking, simultaneous masking, frequency discrimination, nonverbal intelligence, working memory, reading, alerting attention and motor reaction times to auditory and visual stimuli. SCAN-C included monaural low-redundancy speech (auditory closure and speech in noise) and dichotic listening tests (competing words and competing sentences) that assess divided auditory attention and hence executive attention.
Three factors were extracted: “general auditory processing,” “working memory and executive attention,” and “processing speed and alerting attention.” Frequency discrimination, backward masking, simultaneous masking, and monaural low-redundancy speech tests represented the “general auditory processing” factor. Dichotic listening and the IMAP cognitive tests (apart from nonverbal intelligence) were represented in the “working memory and executive attention” factor. Motor response times to cued and noncued auditory and visual stimuli were grouped in the “processing speed and alerting attention” factor. Individuals varied in their outcomes in different tests. Poor performance was noted in different combinations of tests from the three factors. Impairments solely related to the “general auditory processing” factor were not common.
The study identifies a general auditory processing factor in addition to two other cognitive factors, “working memory and executive attention” and “processing speed and alerting attention,” to underlie the deficits in children with susAPD. Impaired attention, memory, and processing speed are known to be associated with poor literacy and numeracy skills as well as a number of neurodevelopmental disorders. Individuals with impairments in the “general auditory processing” tests along with tests from the other two cognitive factors may explain the co-occurrence of APD and other disorders. The variation in performance by individuals in the different tests noted was probably due to a number of reasons including heterogeneity in susAPD and less-than ideal test–retest reliabilities of the tests used to assess APD. Further research is indicated to explore additional factors, and consensus is needed to improve the reliability of tests or find alternative approaches to diagnose APD, based on the underlying factors.