Human activity contains sequential dependencies that observers may use to structure a task environment (e.g., the ordering of steps when tying shoes or getting into a car). Two experiments investigated how people take advantage of sequential structure to understand activity and respond to behaviorally relevant events. Participants monitored animations of simplified human movement to identify target hand gestures. In the first experiment, participants were able to use predictive sequential dependencies to more quickly identify targets. In addition, performance was best at the point in time that followed the sequence. However, the second experiment revealed that how sequential structure affects detection depends on whether the sequence predicts the timing of target events. In all cases, sequence learning was observed without participants' awareness of the sequential dependencies. These results suggest that human activity sequences can be learned without awareness and can be used to adaptively guide behavior.