Separate mechanisms govern the selection of spectral components for perceptual fusion and for the computation of global pitch

The perceptual fusion of harmonics is often assumed to result from the oper ation of a template mechanism that is also responsible for computing global pitch. This dual-role hypothesis was tested using frequency-shifted comple xes. These sounds are inharmonic, but preserve a regular pattern of equal c omponent spacing. The stimuli had a nominal fundamental (FO) frequency of 2 00 Hz (+/-20%), and were frequency shifted either by 25.0% or 37.5% of FO. Three consecutive components (6-8) were removed and replaced with a sinusoi dal probe, located at one of a set of positions spanning the gap. On any tr ial, subjects heard a complex tone followed by an adjustable pure tone in a continuous loop. Subjects were well able to match the pitch of the probe u nless it corresponded with a position predicted by the spectral pattern of the complex. Peripheral factors could not account for this finding. In cont rast, hit rates were not depressed for probes positioned at integer multipl es of the FO(s) corresponding to the global pitch(es) of the complex, predi cted from previous data [Patterson, J. Acoust. Sec. Am. 53, 1565-1572 (1973 )]. These findings suggest that separate central mechanisms are responsible for computing global pitch and for the perceptual grouping of partials. (C ) 2000 Acoustical Society of America. [S0001-4966(00)01503-4].