Randomized Gap Detection Test (RGDT):

The purpose of the RGDT is to identify and quantify temporal processing disorders in children and adults through measurement of gap detection thresholds (GDTs) at four different pure tone test frequencies (0.5, 1, 2, 4 kHz) and clicks. In this study, we only used subtests from the RGDT that contained pure tone stimuli. For each test frequency stimulus pair, the pre- and post-gap tone frequency was identical (e.g., 0.5 kHz tone – gap – 0.5 kHz tone) and had the same duration (17 ms, including a 1-ms rise-fall time). The silent gap duration ranged from 0 to 40 ms (0, 2, 5, 10, 15, 20, 25, 30, and 40 ms). Each gap duration was presented only once and the gap duration was randomized to avoid subject prediction.

The RGDT practice test was administered to familiarize the participant to the test procedure and consisted of 0.5 kHz tone pairs with silent gap durations presented in an ascending order (0, 2, 5, 10, 15, 20, 25, 30, and 40 ms). Next, GDTs were measured for each test frequency (0.5, 1, 2, 4 kHz), using variable gap durations, with the order of test frequency randomized. The task for the listener was to indicate whether one or two stimuli were heard. GDTs were recorded as the shortest gap duration at which the listener correctly indicated that two tones were heard. If the participant failed any frequency (did not indicate two tones were heard at the longest gap duration of 40 ms) contained in the RGDT, indicating a gap detection threshold greater than 40 ms, they were administered the Expanded Randomized Gap Detection Test (RGDT-EXP). The RGDT-EXP administration and scoring is identical to that of the RGDT however it contains longer gap durations ranging from 50–300 ms (50, 60, 70, 90, 100, 150, 200, 250, and 300 ms).