The readback/hearback loop is a communicative protocol employed in many high-risk environments to assure that a verbal instruction has been heard properly by a receiver. However, it does not automatically assure that an instruction has been grasped. Employing an international sample of hydroelectric power generation controllers, this inquiry explored whether specific linguistic (complete and partial readbacks) and prosodic (final intonation, filler, and interturn delay) cues contained within a readback reply could notify to listeners the degree to which speakers had grasped an instruction. The results pointed out that different prosodic cues are employed to discover nonunderstandings, relying upon the linguistic content of the readback. The results have implications for training and system design in distributed environments.