Abstract
Recently, there appeared a large number of studies showing that the results of serial visual search tasks can be explained by uncertainty effects. This explanation implies that search within a single fixation is always parallel and that there is no focal attention performing internal scanning of the search patterns. The present study re-examines the serial search paradigm with a new technique. Instead of measuring mean reaction time for each condition we assessed a histogram of the reaction times accumulated across thousands of trials. The histogram for positive responses (in which target was found) had a flat top, whose width was proportional to the number of distractors. This shape is consistent with serial self-terminating search within a single fixation and inconsistent with the uncertainty prediction.