A functional class refers to a circumstance in which responding is controlled by features of stimuli that are common to all the class members. We argue that behavior with respect to conceptual stimuli entails more than discrimination among classes and generalization within classes. We suggest that an analysis of substitution of stimulus functions may contribute to understanding the distinctions among functional classes of different varieties, including conceptual classes.
Keywords: conceptual stimuli, functional classes, conceptual classes, generalization, discrimination.
Notions such as abstractions, categories and concepts are relevant to the study of verbal behavior and cognition. Since the term "concept formation" was introduced in the behavior analytic literature by Keller and Schoenfeld (1950), it has been used to describe behaviors related to the discrimination of properties of stimuli.
Herrnestein & Loveland (1964), for example, demonstrated successful discrimination in pigeons with respect to pictures of trees, water, people, animals, etc. Their findings were interpreted as indicative of pigeons organizing stimuli into classes just as humans acquire repertoires of verbal categories (Cook, 2002; Sutton & Roberts, 2002).
Interpreting processes of discrimination and generalization as a demonstration of concept formation has resulted in the attribution of complex behaviors to non-human animals. Specifically, it has been suggested that responding differentially with respect to classes of stimuli may be evidence of complex behavioral events such as categorizing, abstracting or relating (Vaughn, 1988; Vonk and McDonald, 2002).
Interestingly, discussions of how these events may be related to verbal behavior or to the study of cognitive events remain unexplored for the most part. As a result, the implications of asserting that organisms acquire concepts are unclear and leave important theoretical issues unresolved. To be resolved is whether animals are capable of cognitive processes historically assumed to be exclusive to humans or if concept acquisition is unrelated to verbal behavior and thereby part of the behavioral repertoire that is common to both humans and animals.
Referring to behavior with respect to properties of stimuli as conceptual behavior adds little to the analysis of stimulus class acquisition. Alternatively, we contend that acquiring a verbal repertoire entails more than discriminative responding with respect to stimulus classes. Rather, it requires the additional component of responding with respect to a stimulus that, being arbitrary in form, substitutes for the shared functions of the class members. We argue that the notion of conceptual responding be restricted to circumstances involving responding of this sort, wherein conceptual behavior may also be characterized as verbal in nature. We will discuss how processes of stimulus and response substitution (see Kantor, 1982) are crucial to the definition of stimulus classes that involve conceptual behavior.
Concepts as Classes of Stimuli
Historically, the terms concepts, categories and classes have been used synonymously. Keller and Schoenfeld (1950) defined a concept as a group of stimuli with respect to which organisms respond similarly, this group being said to constitute a class. Similarly, Zentall, Galizio & Critchfield, (2002) defined categories as classes of stimuli which occasion common responses in a given context.
Different types of concepts have been defined in terms of the number of formal similarities among stimuli in the class. Other distinctions among types of concepts refer to classes of stimuli sharing formal properties versus classes of stimuli sharing functional characteristics only. For example, Zental et al (2002) differentiate perceptual concepts from relational and associative concepts. Perceptual concepts are defined as instances of responding with respect to stimuli that share one or more physical features, while relational concepts refer to responding differentially to more abstract properties of stimuli (e. …