Metacontrol, the regulation of cognitive strategies to balance persistence and flexibility, has been theorized to operate either as a tonic state, maintaining a consistent neural bias, or as a phasic mechanism, dynamically adjusting to situational demands. This study tested these scenarios by examining the relationship between metacontrol biases and changes in the aperiodic exponent of EEG activity. Behavioral results replicated well-established effects. Neural analyses revealed significant post-stimulus increases in the aperiodic exponent during incongruent trials, reflecting enhanced persistence in response to high-conflict conditions. Crucially, the absence of pre-stimulus effects supports the phasic hypothesis, suggesting metacontrol biases emerge dynamically rather than maintaining a stable tonic state. Correlational analyses showed task-specific and transient metacontrol biases. Persistence aligned with high-conflict demands in incongruent trials, while flexibility remained general across conditions. The lack of cross-task correlations between creativity and Flanker tasks further supports the phasic view, where biases adapt to immediate task requirements rather than representing stable traits. These findings align with reactive control theories, emphasizing transient, context-dependent neural adjustments. This study provides evidence for a phasic account of metacontrol, where cognitive control states dynamically shift to meet task-specific demands. This adaptive flexibility underscores the importance of real-time adjustments in human cognition.