Abstract
OBJECTIVES: The purpose of this study was to evaluate the extent to which infants, school-age children, and adults benefit from a target/masker sex mismatch in the context of speech detection or recognition in a background of 2 competing talkers. It was hypothesized that the ability to benefit from a target/masker sex mismatch develops between infancy and the early school-age years, as children gain listening experience in multi-talker environments. DESIGN: Listeners were infants (7 to 13 months), children (5 to 10 years), and adults (18 to 33 years) with normal hearing. A series of five experiments compared speech detection or recognition in continuous two-talker speech across target/masker conditions that were sex matched or sex mismatched. In experiments 1 and 2, an observer-based, single-interval procedure was used to estimate speech detection thresholds for a spondaic word in a two-talker speech masker. In experiments 3 and 4, speech recognition thresholds were estimated in continuous two-talker speech using a four-alternative, forced-choice procedure. In experiment 5, speech reception thresholds (SRTs) were estimated for adults using the forced-choice recognition procedure after ideal time-frequency segregation processing was applied to the stimuli. RESULTS: Speech detection thresholds for adults tested in experiments 1 and 2 were significantly higher when the target word and speech masker were matched in sex than when they were mismatched, but thresholds for infants were similar across sex-matched and sex-mismatched conditions. Results for experiments 3 and 4 showed that school-age children and adults benefit from a target/masker sex mismatch for a forced-choice word recognition task. Children, however, obtained greater benefit than adults in 1 condition, perhaps due to greater susceptibility to masking overall. In experiment 5, adults had substantial threshold reductions and more uniform performance across the 4 conditions evaluated in experiments 3 and 4 after the application of ideal time-frequency segregation to the stimuli. CONCLUSIONS: The pattern of results observed across experiments suggests that the ability to take advantage of differences in vocal characteristics typically found between speech produced by male and female talkers develops between infancy and the school-age years. Considerable child-adult differences in susceptibility to speech-in-speech masking were observed for school-age children as old as 11 years of age in both sex-matched and sex-mismatched conditions.