Skin resistance was recorded from human Ss, while each item of a sequence of visual patterns received 3 successive 3-sec. exposures at 12-sec. intervals. The patterns comprised "less irregular" and "more irregular" items, representing a number of "complexity" and "incongruity" variables. Extrinsically-motivated Ss, i.e., those who were told to attend carefully because they would later undergo a recognition test, produced more frequently GSRs than Ss without such extrinsic motivation. There was a decline in GSR frequency after the 1st exposure of a pattern but a revival when the next pattern appeared. There was also a long-term decline over patterns. Incongruous pictures evoked GSRs of greater mean amplitude than nonincongruous pictures. Some support was obtained for the conclusion that "more irregular" patterns are more likely to evoke GSRs than "less irregular" patterns. (PsycINFO Database Record (c) 2006 APA, all rights reserved)