Perceptual integration of timing and intensity variations in the perception of musical accents

The author investigated the detection of timing and intensity variations in tone sequences within the framework of perceptual independence or integration. The participants listened to sequences of tones that contained variations in timing, intensity, or both. Each participant tried to detect variations in the dimension that was declared relevant, which was either timing or intensity. The irrelevant dimension was held constant, or varied in a manner uncorrelated with the relevant dimension, or varied in a correlated manner. When the variations in the 2 dimensions were correlated, the correlation could be either positive (i.e., timing and intensity created accents in the same sequences) or negative (i.e., timing and intensity created accents in different sequences). Uncorrelated variation in the irrelevant dimension interfered with the detection of variations in the relevant dimension. In the case of a positive correlation between the 2 dimensions, the detection of variations was better than it was with the absence of variation in the irrelevant dimension only for participants who attended to timing. In the case of a negative correlation, the effect was the opposite. The results showed that timing and intensity accents were not processed by completely independent channels. Rather, information from the 2 dimensions combined at a late stage of processing.