To document the trajectory of motor and vocal behaviors in real and developmental time, researchers observed infants at each of 4 biweekly naturalistic play sessions over the transition to crawling. An exhaustive and mutually exclusive coding scheme documented every vocalization and posture. Odds ratios of the likelihood of a given posture-vocalization dyad revealed that vocalization and crawling were significantly unlikely to co-occur at the session marking the onset of crawling. Infants’ allocation of attention over the transition to crawling prompted behavioral trade-offs. During mastery of a novel skill, infants had difficulty allocating attention to multiple tasks, but with experience a decrease in attentional load for the new skill allowed performance of simultaneous behaviors in other domains to occur.