Expansion of the functional visual field and context skipping in a continuous search task

SummaryA new experimental paradigm for the investigation of visual search processes is presented. In a continuous visual search task, the target occurs several times in each search list, and a response is required to each occurrence of the target. The analysis of the data is based on the regression of the interresponse intervals on the distance between successive target occurrences. With a view to measure the size of the functional visual field and the efficiency of “skipping” strategies, the size of letter groups and the minimal distance between successive target occurrences were varied. The rate parameter of the regression functions was used to infer the extent of the functional visual field; the efficiency of “skipping” was assessed on the basis of the intercept. A U-shaped relationship between the size of letter groups and the rate parameter of the regression functions was predicted and found; during practice, the minimum of the U-function shifted from small to large group sizes. This was taken as an indication that the functional visual field expands during practice in a continuous search task. Evidence for efficient “skipping” strategies was found at all stages of practice, subject to the constraint that there was a natural relationship between the size of letter groups and the minimal distance between target occurrences.