Academic journal article Psychonomic Bulletin & Review

A Theory of Variability Discrimination: Finding Differences

Academic journal article Psychonomic Bulletin & Review

A Theory of Variability Discrimination: Finding Differences

Article excerpt

Visual variability discrimination requires an observer to categorize collections of items on the basis of the variability in the collection; such discriminations may be vital to the adaptive actions of both humans and other animals. We present a theory of visual variability discrimination that aggregates localized differences between nearby items, and we compare this finding differences model with a previously proposed positional entropy model across several data sets involving both people and pigeons. We supplement those previously published data sets with four new experiments, three of which involve arrays comprising items entailing systematic, quantitative differences. Although both theories provide strong and similar fits of the published data sets, only the finding differences model is applicable to investigations involving quantitative item differences, providing excellent fits in these new experiments.

People judge variety in a wide range of everyday tasks. We judge the variety of products on a store shelf, racial diversity in our workplace, and restaurant fare in our community. Psychological scientists have found that people exhibit preferences for certain levels of variety (Berlyne, 1960; Munsinger, 1966; Munsinger & Kessen, 1966), and marketing researchers have found that perceived variety has a strong effect on decisions of where to shop (e.g., Baumol & Ide, 1956; Broniarczyk, Hoyer, & McAlister, 1998; Hoch, Bradlow, & Wansink, 1999). As well, nonhuman animals are sensitive to variability when they forage for food (Caraco, 1981; Caraco, Martindale, & Whittam, 1980) or choose mates (McGregor, Krebs, & Perrins, 1981; Searcy, 1984). Yet, despite the clear importance of variability discrimination to adaptive behavior, only recently have researchers begun to explore how we and other species make such discriminations.

Improving our understanding of variability discrimination may change people's behavior. A grocer who knows that customers' shopping preferences are affected by perceived variety can organize store shelves or choose particular flavor combinations to increase the apparent variety of merchandise. The director of an art museum has multiple dimensions of variability to manage (e.g., artist, style, color, and type) and might choose the works to display and their spatial organization in order to maximize perceived variety and thereby avoid ennui in patrons. Given that overeating is more likely with greater variety in food choice (Kahn & Wansink, 2004), a school cafeteria might opt to increase the variety of fruit and vegetable options and to reduce the variety of dessert options. Perceived variability may also underlie judgments of creative behavior (e.g., paintings, music, or fashion), pleasantness, and relevance (highly variable stimuli contain more information). For example, judgments of creativity may be highest for moderate degrees of variability, and the optimal level of variability may increase as a function of experience (cf. Munsinger & Kessen, 1966).

Historically, psychological scientists have focused on a species' ability to filter out variability in both stimuli and responses. The goal of learning was believed to be the isolation of environmental regularities (variability is noise) and the production of consistently reinforced behavior. Some theorists, however, have emphasized the importance of both recognizing and producing variability. For example, Skinner (e.g., 1981) stressed the involvement of response variability in selection by consequences. Other theorists (Ashby & Gott, 1988; Fried & Holyoak, 1984) have stressed the importance of perceived variability to optimal categorization.

In a recent review, Neuringer (2004) examined the production of variability; this work focused on the actor. Our own line of research has examined the observer's discrimination of variability, variability that may be innerent in the environment or produced by other organisms. …

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