Behavioral group d' scores for discriminating chord arpeggios. By convention, discrimination threshold is represented by a d' = 1 (dashed line). Musicians show superior performance (well above threshold) in discriminating all chord pairings, including standard chords in music from versions in which the third is out of tune (i.e., maj/up and min/down). Non-musicians, on the other hand, only discriminate the maj/min pairing above threshold and are unable to accurately differentiate standard musical chords from their detuned versions (i.e., sub-threshold discrimination, maj/up and min/down).