Causal relationships affect perceived audio-visual synchrony : reversed effects for different judgment methods

Subjective synchrony in audio-visual timing perception is typically characterized by the point of subjective equality (PSE). It can be estimated from the 50% point in temporal order judgments (TOJ), or from the center of the synchronous response curve in a synchrony judgement (SJ) procedure. Using both TOJ and SJ procedures, we estimated PSEs for Newton's Cradle, showing a left-to-right pendulum movement. Three visual conditions were used: (1) the entire stimulus, (2) the left, or (3) the right half. In conditions 1 and 2, the visual movement appears to cause the collision, whereas in condition 3 the visual movement appears to result from the collision. Using an SJ procedure, conditions 1 and 2 yielded positive PSEs (i.e. audio delayed relative to video), whereas for condition 3 perceptual synchrony coincided with physical synchrony. Using a TOJ response rule resulted in slightly negative PSEs for conditions 1 and 2, whereas condition 3 yielded highly positive PSEs. Not only do these data show opposite effects for the two response rules, but they indicate strategic variation in the TOJ task. That is, the TOJ PSEs consistently shifted towards the side of the synchrony curve with the steeper slope, indicating the region of greater observer sensitivity