Detection of expected versus unexpected changes

Abstract

The present study investigated the detection of expected and unexpected changes in visual stimuli. Two stimuli for which individuals have schemas about their expected movements were chosen. Stimulus 1 was a ball placed at the upper part of an inclined plane; Stimulus 2 was a clock with visible hour and minute hands. The original stimuli were either followed by its changed version in the expected direction, with the ball sliding down, and the minute hand of the clock moving clockwise, or in the unexpected direction. Results showed that expected changes were detected faster than unexpected ones for the ball stimulus, but not for the clock stimulus. Due to individual differences in response times, the data were more closely inspected by applying median and quartile splits. Results showed that for both stimuli, fastest responders do not show response time differences in the detection of the unexpected and the expected changes. This difference reaches significance in slower responders for both stimuli. We discuss which individual differences may differentiate slow responders from the fast ones. We also discuss the differences between the two stimuli we used with regard to the types of schemas they are likely to form. These results also suggest that changes that are consistent with schemas do not require further controlled processing and are detected faster.