The Role of Gist Processing in Boundary Extension.

Boundary extension is a ubiquitous phenomenon in which participants remember seeing more of an image than was previously shown. According to the Multisource Model of Scene Perception, viewers create a representation of their environment within a single fixation that integrates presented scene information with their expectations of what should exist there. The purpose of the following experiments was to determine the extent to which boundary extension relies on gist processing, and particularly, whether access to certain scene gist properties could be used to explain previous findings in the boundary extension literature. The gist of the scene is readily available at short timespans and was hypothesized to facilitate the existence of boundary extension by contributing schematic information about the scene into the representation. By shortening the encoding duration, access to the gist was gradually reduced to threshold levels. Experiment 1 was used to determine whether boundary extension could be elicited with natural complex scenes. The results from Experiment 1 showed that boundary extension could be elicited from complex natural, landscape scenes; however, it heavily depended on the participants' perceived depth rating and their perceived navigability of the scene. Experiment 2 manipulated access to the mean depth gist property and showed that boundary extension decreased as access to the gist was reduced, whereas Experiment 3 manipulated access to the navigability gist property and found that boundary extension increased as access to the gist was reduced. Experiment 2 provides evidence that the gist property depth is essential to the existence of boundary extension, making available schematic information to our scene representation which leads to increases in the source monitoring error. Experiment 3 shows evidence that navigability also provides schematic information to our scene representation however due to the adaptive function of the property it serves to provide veridical memory for the scene. Meeting abstract presented at VSS 2015.