Overall performance per ISI in the NA group remained constant at longer intervals (100–400 ms) and declined as the intervals shortened, from 50 ms onwards, in both ears and at both SNRs. All analyses were conducted using generalized models due to their flexibility in dealing with data with non-normal and/or heteroscedastic distribution. For the GEEs, independent covariance matrix structures were considered for the GEEs and log link functions were used for all generalized models. BMT measures were compared between the three study groups by generalized linear models (GzLM) considering a gamma distribution for BMTT and a normal distribution for BMTP, with post hoc analysis using t-tests with sequential Bonferroni correction for multiple comparisons. To verify the effect of ear and SNRs on the BMTT and BMTP measures in the NA group, GEEs with inverse Gaussian distributions for the dependent variables (BMTT and reverse-transformed BMTP) were built. In order to investigate the presence of interactions between the effects of SNR, ear and ISI duration on performance in the BMT in the NA group, a generalized estimated equation (GEE) model considering a binomial negative distribution for the dependent variable (reverse-transformed number of hits), was built.
The data were submitted to descriptive analysis by calculating measures of central tendency and dispersion. Normative values were obtained for the BMT, which proved to be clinically feasible, with preliminary evidence of validity. Results were more consistent at SNR −20 dB, and the best diagnostic accuracy was obtained for SNR −20 dB, with good specificity, but low sensitivity. Young adults with normal ATP obtained an average correct response rate of 89 and 87% for SNR −20 and −30 dB, respectively, with average thresholds between 10 and 15 ms and no difference between the left and right ears. Diagnostic accuracy analyses were carried out. The correct response rate and target sound detection threshold were calculated, and the results compared with those of young adults with abnormal ATP tests and older adults. Young adults were submitted to a BM test (BMT), where they were asked to identify a 1000 Hz pure tone followed by a narrowband noise with interstimulus intervals of 0 to 400 ms and signal-to-noise ratio (SNR) between −20 and −30 dB. The aim of this study was to develop, standardize and present evidence of validity for a behavioral test for BM assessment. There are still no valid, clinically feasible instruments to assess backward masking (BM), an auditory temporal processing (ATP) phenomenon.