Time stretching: Illusory lengthening of filled auditory durations

The second of two consecutively presented sounds may be perceivedas being longer than if that sound had been presentedin isolation. Weperformedfive experimentsusingheterophonicpatterns in whicha sinetone was precededby a frequency-band noise. Weobserved significantoverestimations of sine-toneduration,the size of whichdependedon intensityandfrequency differencesbetweenthebandnoise and the sinetone(Experiments1 and 2). Band noises that were considerably shorter than the sine tone still caused significant overestimations (Experiment3). A short silent gap between the band noise and the sine tone strongly reduced the amount of overestimation (Experiment4). Bothfrozenand nonfrozenbandnoisesyielded overestimations (Experiment5). Ourexplanation for the overestimation is that the onset of the sinetone is blurred by the bandnoiseand that such a blurred onset is restored at the level of perceptual organizationfollowingrules of a simpleauditorygrammar. This restorationtakes mentalprocessingtime, which addsto the perceivedduration of the sine tone. Wecall this illusiontimestretchingand discuss the notion that subsequenttemporalassimilation and/orcontrasteffects can dilate or compressthe amount of stretching.