Different cognitive processes in two image-scanning paradigms

Mental image scanning is generally assumed to be a single process that allows people to shift attention across visualized objects. However, this implicit assumption is open to question. We report a set of three experiments based on the tasks originally designed by Kosslyn, Ball, and Reiser (1978) and Finke and Pinker (1982). Participants scanned the identical images of an array of dots in the two tasks. Nevertheless, the participants required more time to shift their focus over the imaged stimulus in the Kosslyn et al. (1978) paradigm. Moreover, correlational analyses revealed no consistent relationship between the slopes of the increases in scanning times with increasing distances in the two paradigms. We conclude that in the Kosslyn et al. (1978) paradigm, the participants draw primarily on transformational processes to scan, whereas in the Finke and Pinker (1982) paradigm, they draw primarily on attentional processes. Both processes, transforming the image and shifting an attention window, produce linear increases in time with increases in distance, but for different reasons.