Academic journal article Attention, Perception and Psychophysics

Region Segmentation and Contextual Cuing in Visual Search

Academic journal article Attention, Perception and Psychophysics

Region Segmentation and Contextual Cuing in Visual Search

Article excerpt

Contextual information provides an important source for behavioral orienting. For instance, in the contextual-cuing paradigm, repetitions of the spatial layout of elements in a search display can guide attention to the target location. The present study explored how this contextual-cuing effect is influenced by the grouping of search elements. In Experiment 1, four nontarget items could be arranged collinearly to form an imaginary square. The presence of such a square eliminated the contextual-cuing effect, despite the fact that the square's location still had a predictive value for the target location. Three follow-up experiments demonstrated that other types of grouping abolished contextual cuing in a similar way and that the mere presence of a task-irrelevant singleton had only a diminishing effect (by half) on contextual cuing. These findings suggest that a segmented, salient region can interfere with contextual cuing, reducing its predictive impact on search.

A fundamental task of the human information processing system is to structure the complex input from the ambient visual array. Perceptual grouping provides one mechanism that integrates fragmentary parts into coherent units or objects while segregating it from other, neighboring objects and from the background (see Roelfsema, 2006, for a review). Although it is believed that image segmentation is primarily bottom-up driven, there are also studies suggesting that it can be influenced by previously acquired knowledge, for instance, by exploiting shape familiarity (e.g., Nelson & Palmer, 2007; Vecera & Farah, 1997) or the statistical covariation of objects (Baker, Olson, & Behrmann, 2004) and their spatial relations (Chun & Jiang, 1998). For example, in Chun and Jiang's study, learned contextual layouts facilitated target detection in subsequent trials. Thus, both grouping and contextual learning establish relational structures, either by means of bottom-up segmentation or by means of retrieving learned contextual associations. Here, we investigate how both processes, grouping and contextual learning, interact with each other.

Perceptual grouping has originally been shown to follow a set of basic principles in imposing structure on fragmentary information (Koffka, 1935). In many cases, grouped items allowed more efficient processing than did the corresponding processing of individual component parts. For instance, configural properties are processed more efficiently than individual features are (Pomerantz, Sager, & Stoever, 1977), and studies on visual search have shown that the individual parts may be integrated into a coherent representation prior to the engagement of attention (e.g., Moore & Egeth, 1997; Rensink & Enns, 1995). Also, search for a coherent object (composed from individual items/elements that can be grouped to form a global object representation) may be more efficient than is search for the same basic elements if these are presented such that no integrated object can be established (Conci, Müller, & Elliott, 2007b; Found & Müller, 1997; see also Friedman-Hill & Wolfe, 1995). In accordance with the basic Gestalt principles, low-level grouping mechanisms have been shown to structure visual input according to a variety of general laws, such as similarity (Duncan, 1984; Duncan & Humphreys, 1989), closure (Conci, Müller, & Elliott, 2007a; Donnelly, Humphreys, & Riddoch, 1991), and proximity (Han, Humphreys, & Chen, 1999). For instance, Conci et al. (2007a) demonstrated that visual search for a collinear line grouping is guided by the integrated representation of a closed shape. More specifically, search for a closed target configuration (composed from Ls arranged to form a square grouping) among open distractor configurations (arranged to form an open cross shape) was more efficient than was search for an open (cross-shaped) target configuration among closed square distractors, even though the local contrasts between elements making up the configurations were held constant. …

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