Effect of initial-consonant intensity on the speed of lexical decisions

In the present study, we investigated the effect of initial-consonant intensity on lexical decisions. Amplification was selectively applied to the initial consonant of monosyllabic words. In Experiment 1, young adults with normal hearing completed an auditory lexical decision task with words that either had the natural or amplified initial consonant. The results demonstrated faster reaction times for amplified words when listeners randomly heard words spoken by two unfamiliar talkers. The same pattern of results was found when comparing words in which the initial consonant was naturally higher in intensity than the low-intensity consonants, across all amplification conditions. In Experiment 2, listeners were familiarized with the talkers and tested on each talker in separate blocks, to minimize talker uncertainty. The effect of initial-consonant intensity was reversed, with faster reaction times being obtained for natural than for amplified consonants. In Experiment 3, nonlinguistic processing of the amplitude envelope was assessed using noise modulated by the word envelope. The results again demonstrated faster reaction times for natural than for amplified words. Across all experiments, the results suggest that the acoustic-phonetic structure of the word influences the speed of lexical decisions and interacts with the familiarity and predictability of the talker. In unfamiliar and less-predictable listening contexts, initial-consonant amplification increases lexical decision speed, even if sufficient audibility is available without amplification. In familiar contexts with adequate audibility, an acoustic match of the stimulus with the stored mental representation of the word is more important, possibly along with general auditory properties related to loudness perception.