EN
The question whether attention is a unitary concept or not is still unanswered. Allport suggested possibility of autonomic modules of attentional system, whereas Kahneman postulated mechanism of attentional distribution of common mental energy resources. In three independent experiments (N = 59, N = 62, N = 102) three models of attentional control was tested: unitary model (controled processing), partial model (autonomic processing) and mixed model (controled processing on the global level and autonomic processing on the local level). Three version of the DIVA test of selective and divided attention was employed. The test versions differed in task difficulty. The divided attention costs were observed in each study. However, the type of attentional control depended on task difficulty. Unitary and mixed models were confirmed, whereas it appeared impossible to test partial model due to relative difficulty of each used version of the DIVA test. Attention seems to be not only unitary system, but also flexible, changing the type of control due to the task difficulty.