This study has identified regions of the frontal lobe that respond selectively to visual stimuli in which the elements occur in an irregular temporal sequence. Given the brain locations that show the greatest response, one might wonder whether detecting a lack of regularity in a sequence draws on working memory. Subjects were asked to decide whether or not a sequence was regular, so one might expect working memory to be holding early portions of the message for comparison to later portions. However, one would think the demand on working memory would be the same whether or not the sequence repeated, so it is not clear why degree of activation should be greater for irregular stimulus patterns. ‘Tis a puzzle.