Fig. 1.

Experimental design of the presented task. Four squares were displayed horizontally across a screen. The squares were individually illuminated in one of three randomly selected colors (blue, red, or yellow) for 1 sec. Beginning at 100, participants kept a mental count of the total number of blue squares presented during the entire session. The sequence of spatial positions illuminated was determined by an artificial grammar with the entropy of the sequence varying between condition blocks. The given example illustrates 4 sec of a scan where the spatial sequence was presented (1-3-2-4). The occurrence of functional scans and the subject's mental count of the blue squares are also shown.