Design of the experiment.

<p><b>A.</b> A schematic diagram of the setup used for AF perturbation during speech. <b>B.</b> A schematic showing an example of the ordering of the noPert (baseline), Down, and Up trials in Experiment 1. Note the rule that two perturbation trials were separated by at least one intervening noPert trial. <b>C.</b> Example spectrograms of the monophthong [ε] in the word “head”: the original (noPert) spectrogram (left), 20% Up shift (center), and 20% Down shift (right). The dashed white curves show the original tracked F1 trajectories; the dashed cyan curves display the perturbed F1 trajectories.