Visual categorization and identification of unattended objects: are faces unique?
36.42, Sunday, May 12, 2:45 - 6:45 pm, Orchid Ballroom
Nurit Gronau1, Rotem Amar1, Anna Izoutcheev1, Vladimir Kalendarev1; 1Department of Psychology, The Open University of Israel
The extent to which visual stimuli are recognized in the absence of attention is under dispute. While several researchers have argued that real-world objects can be detected and categorized when presented at an unattended location, other have provided evidence against such 'attention-free' findings. Most studies have used dual task paradigms, in which participants perform a highly demanding task, while simultaneously detecting a pre-specified object category appearing at a peripheral location (e.g., an animal or vehicle). We sought to examine pre-attentive object processing using a different approach, in which objects are strictly irrelevant to task-requirements and to response-selection processes. In a series of studies we demonstrated that, despite its irrelevance to task demands, participants are sensitive to object categorical identity when stimuli are presented inside, but not outside the focus of visual attention. Our results suggested that when unattended objects are strictly task-irrelevant they are not automatically categorized and identified. In the present research we asked whether faces form a unique class of stimuli that can be categorized pre-attentively. Using an experimental paradigm identical to our previous research, we have obtained a 'categorical effect' for task-irrelevant faces appearing outside the main focus of visual attention, indicating that the latter are categorized involuntarily. A possible account, however, for this finding is the low interstimulus perceptual variance among facial stimuli, relative to superordinate categories such as animals and vehicles. Indeed, when examining houses, chairs, and cars, a similar categorical effect was obtained for the unattended stimuli. These findings indicate that narrow, highly distinct, categories may be benefit from automatic pre-attentive processing. Faces, then, may not be special relative to other basic-level categories. Finally, an additional set of experiments suggests that famous faces may be detected and recognized at the subordinate level even when unattended, presumably due to our extensive experience with such stimuli.