The study protocol was a modification of our earlier auditory target detection (oddball) paradigms using tonal and phonetic stimuli,10,33 as already described in detail.48 Briefly, stimuli were either two complex tones, consisting of 250-ms square waves (25 ms rise and decay time) with fundamental frequencies of 444 and 485 Hz corresponding to the major notes A4 and B4, or two consonant-vowel syllables (/da/, /ta/), spoken by a male voice and approximately matched to the complex tones by discriminability, duration, and root mean squared amplitude (cf. Figure 1 in Kayser and Tenke48). These tonal (T) and phonetic (P) stimuli have been shown to produce opposite perceptual asymmetries in dichotic listening studies (e.g.,67,68), and therefore provide a probe of cognitive processes predominantly performed by the right or left hemisphere. All stimuli were presented binaurally via a matched pair of TDH-49 earphones at a comfortable hearing level (72 dB SPL), with earphone orientation counterbalanced across participants.
