Fractal Coordination in Adults ’ Attention to Hierarchical 4 Visual Patterns

A display that contains hierarchically nested levels of order requires 11 the perceiver to selectively attend to one of the levels. We investigate the degree 12 to which such selective attention is sustained by a soft-assembled emergent 13 coordinative process, one that does not require designated executive control. In 14 the case of emergent soft-assembly, performance from one trial to the next 15 should show characteristic interdependence, visible in the fractal structure of 16 reaction time. To test this hypothesis, we asked participants across three 17 experiments to decide whether two displays matched in a certain way (e.g., in a 18 local element). In order to gauge this coordinative process, task constraints 19 were experimentally manipulated (e.g., familiarity, predictability, and task 20 instruction). Obtained reaction-time data were subjected to a spectral analysis 21 to measure the degree of interdependence among trials. As predicted, results 22 show correlated structure across trials, significantly different from what would 23 be predicted by an independent-process view selective attention. Results also 24 show that the obtained spectral scaling exponents track the degree of coupling 25 in the task as a function of the degree of task constraints. Findings are discussed 26 in terms of the relative organism-environment coupling to sustain an adaptive 27 behavior. 28