The study of the coordination of attention, a term called joint attention (JA), has resulted in a better understanding of the dynamics and development of communication. Despite the important insights gained from studying JA, there is little consensus regarding the specific components that are included in operationalizing JA. The present work explored a parameter space of JA during a dyadic naturalistic toy play task between 9-month-old infants and their parents. We systematically measured the temporal properties of two components commonly used to operationalize JA: the duration of continuous alignment of parent and infant visual fixations and the flexibility of fluctuations of attention. The results show that very brief bouts of JA are important predictors for vocabulary development. The results from this work provide new insights into the specific properties used to operationalize JA and point to the importance of considering multiple timescales of behavior that make up JA.