Diagnostic Precision of Open-Set Versus Closed-Set Word Recognition Testing

Purpose The aim of the study was to examine the precision of forced-choice (closed-set) and open-ended (open-set) word recognition (WR) tasks for identifying a change in hearing. Method WR performance for closed-set (4 and 6 choices) and open-set tasks was obtained from 70 listeners with normal hearing. Speech recognition was degraded by presenting monosyllabic words in noise (-8, -4, 0, and 4 signal-to-noise ratios) or processed by a sine wave vocoder (2, 4, 6, and 8 channels). Results The 2 degraded speech understanding conditions yielded similarly shaped, monotonically increasing psychometric functions with the closed-set tasks having shallower slopes and higher scores than the open-set task for the same listening condition. Fitted psychometric functions to the average data were the input to a computer simulation conducted to assess the ability of each task to identify a change in hearing. Individual data were also analyzed using 95% confidence intervals for significant changes in scores for words and phonemes. These analyses found the following for the most to least efficient condition: open-set (phoneme), open-set (word), closed-set (6 choices), and closed-set (4 choices). Conclusions Closed-set WR testing has distinct advantages for implementation, but its poorer precision for identifying a change than open-set WR testing must be considered.