Academic journal article Memory & Cognition

Different Cognitive Processes in Two Image-Scanning Paradigms

Academic journal article Memory & Cognition

Different Cognitive Processes in Two Image-Scanning Paradigms

Article excerpt

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.

Research on mental imagery over the past 20 years has two interesting overarching characteristics. The first is the genuine gains in our empirical knowledge of this form of representation. Today, there are few disagreements about the empirical facts regarding mental imagery, even when the interpretation of some of them remains a matter of controversy (Kosslyn, Ganis, & Thompson, 2003; Pylyshyn, 2002). The second characteristic is that the study of mental imagery not only has benefited from classic experimental methodologies, but also has sparked the creation of new paradigms. The present research builds on previous discoveries about how visual mental images are processed and focuses on paradigms created to study such processing. Specifically, we ask whether two paradigms designed to study mental image scanning in fact tap the same underlying processes; if not, this phenomenon is more complex than is often assumed.

The first image-scanning paradigm was developed to investigate the spatial properties of images (Kosslyn, 1973). In the original experiment, participants memorized drawings of elongated objects (such as a tower). Afterward, they were asked to close their eyes, visualize one of the drawings, and mentally focus at one end of the depicted object (e.g., the bottom of the tower). Then they heard the name of a possible part or property of the imaged object (a clock on the façade, a flag on the roof, etc.) and were to "look for" it (keeping their eyes closed). In this task, the participants were never told to scan over the object in the image but, instead, were told that they needed to focus on the original location until the probe was delivered and then to focus on the named part or property (if they could find it on the imaged object). When they had focused on the named part or property-or the region where it should have been if it had been present, when it had not, in fact, been included on the drawing-they pressed one of two buttons. If they were able to focus on the named part or property (because it had been included in the drawing), they pressed one button; if they were focused on the appropriate location but the named part or property was not present, they pressed the other button. Three different distances separated the point of initial focus and the location of the named part or property, and the longer the distance, the more time the participants took to respond. This finding was taken as evidence that distance, as traversed by image scanning, is represented in visual mental images.

A variation on this first image-scanning paradigm was later used by Kosslyn, Ball, and Reiser (1978). The new features were that focus and probe locations did not have intervening objects, 21 distinct distances were traversed, and attention needed to be shifted over two dimensions. Kosslyn et al. (1978) designed a map of an island containing seven landmarks (a beach, a rock, etc. …

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