Do infants perceive invariant tempo and rhythm in auditory-visual events?

Two experiments tested 7-month-old infants' ability to categorize events on the basis of invariant rhythm or tempo. Videotaped auditory-visual events (a hammer striking a surface to create characteristic rhythms and tempos) were presented to infants using an habituation procedure. In Experiment 1, following habituation to events depicting one tempo amid three rhythms, infants showed a significant recovery of visual attention to a change in tempo and rhythm, but not to a change in rhythm alone. In Experiment 2, following habituation to events displaying one rhythm amid three tempos, infants did not show a recovery of visual attention to a change in rhythm and tempo, nor to a change in tempo alone. The pattern of results suggested that 7-month-old infants categorized events on the basis of invariant tempo amid changing rhythms, but did not appear to do so for an invariant rhythm in the context of changing tempos.