Pupil responses in Experiment 1.

Mean pupil traces across four SNR conditions, measured for 21 listeners in Experiment 1. Traces are expressed in absolute unit (top) or relative to the 1-sec baseline (bottom). Three metrics were extracted: Baseline (top-right), PPD amplitude (bottom-middle), and PPD latency (bottom-right). The pupil dilated more at 0 dB than any other SNR. Error bar and shaded width represents 1 standard error from the mean.