Figure 1. Stimuli and experimental design.

A, Auditory stimuli consisted of an ascending tone in which portions were replaced by noise bursts, as illustrated by the sound spectrogram. B, Trials comprised an adaptor stimulus presented twice and a subsequent target stimulus. Listeners judged the continuity of the stimuli during visually cued response intervals. C, For the interrupted target stimuli, the relative amplitude of the tone and noise (SNR) was defined individually from thresholds for the continuity illusion of the interrupted tone (−6.8 dB on average). The uninterrupted target stimuli were physically identical to the interrupted target stimuli, except that the tone was physically uninterrupted. D, In experiment 1, the adaptors comprised relatively loud or soft noise, or no adaptors were presented. E, In experiment 2, the same stimuli as in experiment 1 were presented differently, i.e, the adaptors and target within each trial were presented either to the same ear or to opposite ears. F, For experiment 3, physically identical, perceptually ambiguous adaptor stimuli were used that were identical to the interrupted target stimuli. ‘Subjective’ adaptor conditions were created post hoc by sorting trials according to how listeners had judged the ambiguous adaptors (i.e., as either continuous [‘cont.’] or discontinuous [‘disc.’]).