The tacit and incidental acquisition of sequential information can occur in tasks from air-traffic control to crossing the streets in a crowded metropolis. The present study investigated how implicit sequence learning occurs when attention is divided amongst tasks. Our conceptualization of implicit sequence learning is that dual task interference arises from multiple control processes in the secondary task. This fits with findings that implicit learning remains intact when a within stimulus dual task is employed, where the stimulus for both tasks is incorporated within a single stimulus. However, a direct comparison with the standard dual task condition has not been presented. This comparison revealed another possible explanation for dual task interference in implicit sequence learning, that longer inter-trial intervals, a function of the within stimulus methodology, result in better performance and implicit learning. The data suggest that implicit learning and overall performance in a task that contains an incidental, consistent structure is optimized when stimuli are contained within a single stimulus.