Proactive and reactive modes of cognitive control can operate independently and simultaneously.

Cognitive control enables optimal biasing of attention, perception, and actions in the service of mental or behavioral goals. To understand the variability of applied cognitive control, we need to unravel the relation between two underlying mechanisms: proactive and reactive modes. During proactive cognitive control, goal-relevant information is selected before the occurrence of a cognitively demanding event, and is actively maintained for as long as required by the task. During reactive mode, cognitive control is transiently activated only after the cognitively demanding event has occurred. Mechanistically, proactive and reactive control modes may be at least semi-independent and engaged simultaneously, but this has so far not been demonstrated empirically. Situational demands and an individual's cognitive capacity and motivation may bias behavior towards one or the other mode. Reward induces more proactive processing in the AX-CPT task, whereas context load induces reactive processing. We combined these manipulations to investigate the extent to which proactive and reactive control modes can operate independently and simultaneously. The results replicated already published effects of reward incentives and context load. Most importantly, these effects were essentially independent of each other, suggesting that proactive and reactive cognitive control modes depend on separate information-processing and neural mechanisms. The results also show that while proactive processing is influenced by reward, reactive processing seems independent of such factor. These findings have implications for our understanding of the structure of cognitive control and cognitive motivation, and are relevant for the design of interventions to improve cognitive control in various developmental and neuropsychiatric groups.