Academic journal article Attention, Perception and Psychophysics

Associative Grouping: Perceptual Grouping of Shapes by Association

Academic journal article Attention, Perception and Psychophysics

Associative Grouping: Perceptual Grouping of Shapes by Association

Article excerpt

Perceptual grouping is usually defined by principles that associate distinct elements by virtue of image properties, such as proximity, similarity, and occurrence within common regions. What role does learning play in forming a perceptual group? This study provides evidence that learning of shape associations leads to perceptual grouping. Subjects were repeatedly exposed to pairs of unique shapes that co-occurred within a common region. The common region cue was later removed in displays composed of these shapes, and the subjects searched the display for two adjacent shapes of the same color. The subjects were faster at locating the color repetition when the adjacent shapes with the same color came from the same trained groups than when they were composed of two shapes from different trained groups. The effects were perceptual in nature: Learned pairings produced spatial distortions similar to those observed for groups defined by perceptual similarity. A residual grouping effect was observed even when the shapes in the trained group switched their relative positions but was eliminated when each shape was inverted. These results indicate that statistical co-occurrence with explicit grouping cues may form an important component of perceptual organization, determining perceived scene structure solely on the basis of past experience.

A fundamental challenge for vision science lies in determining how humans detect and understand structure in the visual environment. Historically, the processes that create an organized percept have been seen as driven primarily by stimulus properties, such as texture continuity, similarity and proximity of distinct elements, and the presence of cues to region and connectedness in the image (Palmer, 1992; Palmer & Rock, 1994; Wertheimer, 1923). Vision scientists have long viewed perceptual organization as a set of processes that precede object recognition and the operation of visual attention (e.g., Marr, 1982; Neisser, 1967; Treisman, 1982), and Gestalt psychologists especially viewed these processes as largely independent of experience (e.g., Gottschaldt, 1926; Wertheimer, 1923). However, some of these views have been challenged in recent years. For instance, Peterson and colleagues provided evidence that figure-ground segmentation, a fundamental component of perceptual organization, is profoundly influenced by knowledge of familiar shapes (Peterson & Gibson, 1994; Peterson, Harvey, & Weidenbacher, 1991). This influence of learning on perceptual organization opens up the possibility that learning may also alter the perceptual grouping of distinct visual elements, a notion taken for granted by recent theories of grouping (Roelfsema, 2006; Ullman, 2007). However, as will be reviewed below, empirical evidence for how learning affects perceptual grouping remains ambiguous. Here, we attempt to answer the question, Can two shapes become so strongly associated through learning that they are unintentionally grouped?

In this article, we address perceptual grouping, which must be distinguished from other perceptual organization processes, such as texture segmentation (resolution of a continuous region on the basis of textural differences) and figure-ground segmentation (assignment of depth to elements of a scene that border one another in the image). Perceptual grouping binds together distinct elements that do not necessarily share borders in an image (Palmer & Rock, 1994). Perceptual space around the grouped items is warped (Coren & Girgus, 1980), and attention spreads within groups or preferentially selects grouped elements (Dodd & Pratt, 2005; Marino & Scholl, 2005). The outcome of perceptual grouping is a representation that is, on some level, treated as a whole by attention and perception, even though it clearly consists of distinct and, often, widely separated elements.

Previous Demonstrations of Experience Effects in Grouping

Recent evidence suggests that experience plays a significant role in some aspects of perceptual grouping. …

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