Duration, but not intensity cues, facilitate synchronization to complex rhythms.

Rhythm emerges from the temporal patterning of sounds and the expectations that shape how we hear them. Rather than passively listening to incoming events, listeners organize timing information through internal predictions and external acoustic cues. In speech, louder sounds tend to mark the start of a group, whereas longer sounds mark its end, a pattern described by the Iambic-Trochaic Law (ITL) that supports segmentation and word learning. We asked whether this perceptual grouping principle in speech could also facilitate synchronization to musical rhythms. Thirty-six adults with minimal musical training tapped along to tone sequences in simple (4/4) or complex (7/8) meters, each presented with neutral, ITL-aligned, or reverse (ITL-reversed) contours. Synchronization accuracy showed no contour effects for simple meter, but contour effects emerged in complex meter, where reverse contours produced the most accurate tapping. Error analyses indicated that prosodic contours encouraged cautious timing relative to reverse, whereas reverse contours yielded more consistent beat tracking with fewer missed taps and fewer extra taps. These findings suggest that a long initial note provided an attentional anchor that stabilized timing, and that under the conditions tested here, duration cues yielded larger and more reliable synchronization benefits than intensity cues. Thus, intensity and duration cues may guide musical timing through distinct, attention-based mechanisms.