However, all these studies cross-sectionally compare highly specialized individuals with a group of non-experts and this type of approach does not allow conclusions on the origins of this variability. The impact of different life experiences, like taxi driving, language learning, or music skills, has been addressed in studies investigating inter-individual variability in brain structure and function.
Despite a large interest in explaining the sources of individual variability, little is known on the development of different cognitive control processes and how they are shaped by specific life experiences. According to the model, both inter- and intra-individual variability can be better understood by assuming different reliance on proactive and reactive control strategies. The former is characterized by sustained and anticipatory maintenance of goal-relevant information, while the latter is described as a transient, bottom-up reactivation of behavioral goals. To account for the empirically observed variability in cognitive control function, Braver proposed the Dual Mechanism of Control (DMC) framework, which distinguishes two cognitive control modes: proactive and reactive. Although there is a general agreement that this flexibility leans upon specialized cognitive control mechanisms that allow goal-directed behavior, it would be implausible to assume that all individuals rely equally on these mechanisms and adopt always the same strategies when acting in a goal-directed manner. The uniqueness of human cognition derives from the flexibility in adapting thoughts and behaviors to rapidly changing internal and external states. This experience-based enhancement of reactive control strategy denotes how cognitive control and executive functions in general can be shaped by real-life training and underlines the importance of experience in explaining inter-individual variability in cognitive functioning.
These results indicate a training-induced change in reactive control, which is described as a transient process in charge of stimulus-driven task detection and resolution. Critically, the training that the ATCs underwent improved their accuracy in general and reduced response time switching costs during short CTIs only. Being more capable in managing multiple task sets and less distracted by interfering events suggests a more efficient selection and maintenance of task relevant information as an inherent characteristic of the ATC group, associated with proactive control.
However, this advantage was present also prior to the training phase. The results showed that the ATCs, with respect to the control group, had substantially smaller mixing costs during long cue-target intervals (CTI) and a reduced Stroop interference effect. A group of ATC trainees and a matched group of university students were tested longitudinally on task-switching and Stroop paradigms that allowed us to measure indices of cognitive control. In particular, specific life experiences, like a highly demanding training for future Air Traffic Controllers (ATCs), could modulate cognitive control functions. For instance, different reliance on proactive versus reactive control strategies could explain inter-individual variability. Although human flexible behavior relies on cognitive control, it would be implausible to assume that there is only one, general mode of cognitive control strategy adopted by all individuals.