Figure 1. Experimental design.
A. Trial structure. Passive trials begin with a visual fixation point bracketed by “<>”. Attention trials begin with an auditory cue indicating the location and pitch of the to-be-attended melody. The auditory mixture always begins with a center melody (grey waveform). The leading and lagging melodies then begin 0.60 and 0.75 s after the center (red and blue waveforms, respectively). The response period, marked by a circle surrounding the fixation point, begins at 3.5 second. Visual feed back was given for 300 ms after the response period (a blue dot to indicate a correct answer or a red dot to indicate an incorrect answer).
B. Schematic spectrogram of stimuli for the three melodies in different-pitch and same-pitch conditions.
C. Illustration of the hypothesized difficulties of the four different trial types.
