Does SAE have /flap/? Evidence from Canadian Raising and Vowel Durations

In American English, /t/ and /d/ neutralize to flaps intervocalically: write ∼ writer and ride ∼ rider.  There also exist words which contain ambiguous surface flaps that do not alternate, for example, the name Ryder . Does the language user treat this flap like an allophone of /t/ or /d/ (as predicted by the Free Ride Principle), or as an independent segment (as predicted by Lexicon Optimization)? To investigate this question, acoustic data from elicited (Experiment 1) and spontaneous (Experiment 2) speech are analyzed. Voiceless consonants cause the vowel preceding them to be shorter and trigger Canadian Raising. Therefore, if language users treat non-alternating flaps as allophones of /t/, the vowel durations and F1 trajectories of the vowels in these two environments will be similar to each other and different from before flapped /d/, and vice versa if language users treat non-alternating flaps as allophones of /d/. If language users treat non-alternating flaps as different than both the flap allophones of /t/ and /d/, vowel durations and F1 will be different in all three environments. Results show that the durations and F1 trajectories of the vowels in the three environments are all different from each other, providing evidence for Lexicon Optimization.