Effects of bilateral alternation on perceived temporal uniformity of auditory and somesthetic pulse trains

Certain attempts to account for the apparent loss of information when stimuli are presented in rapid alternation between the two sides of the body imply that some elements of the alternatingstimulus train are deleted. This implication forces the prediction that the train of surviving stimuli will be nonuniformly spaced. Yet observers do not report such temporal nonuniformity. The perceptibility of actual nonuniformity in stimulus trains was here found to be strikingly poorer for bilaterally alternating than for unilateral pulses, a finding qualitatively consonant with deletion models. Quantitatively, however, thresholds for perceived nonuniformity were so low as to require that deletion models include a mechanism allowing central respacing of the surviving train. “Stream segregation” is considered as an alternative to deletion models.