What mediates infants' and adults' superior processing of the major over the augmented triad?

In this paper, the claim that the major triad has special status for infant as well as adult listeners is evaluated. In Experiment 1, infants and adults were required to detect a downward semitone change in a fivenote melody based on the major triad and in another five-note melody based on the augmented triad. Both infants and adults performed significantly better on the major triad melody. In Experiment 2, infants and adults were evaluated on their detection of a downward semitone change in a five-note melody that incorporated a perfect fifth or augmented fifth relation but that also contained non-Western intervals. Again, infants and adults performed significantly better on the melody that incorporated the perfect fifth relation. These findings imply that enhanced processing of perfect fifth relations may account for infants' and adults' effective processing of the major triad.