Editorial: Basic and translational research on stimulus-stimulus relations.

One of the great challenges for a behavioral science is to provide an account of emergent stimulus–stimulus relations not explained by primary stimulus generalization. For example, the relation between the visual stimulus dog and the sound made when someone says “dog” is often referred to as arbitrary because the two stimuli have no point-to-point correspondence (one is a sound, the other a creature incapable of making the sound “dog”). In humans, through natural language training, these two stimuli are related (an activity) such that they may occasion similar responding. For example, a child suffering from a dog phobia may experience an increased heart rate and jump into the arms of a parent who says, at the front door of a friend’s house, “They have a dog,” just as he would if he saw the dog. This two-member class of arbitrarily related stimuli is expanded when the verbal response “perro” is related as equivalent to “dog” and, subsequently, hearing “They have a perro” elicits the same fear responding in the dog-phobic listener. Emergent stimulus relations have been of interest since the beginnings of experimental psychology (e.g., Anrep, 1923; Bass H Hull, 1939; Shipley, 1933) and since that time, an extensive taxonomy of the variety of stimulus–stimulus relations has been created (see Murphy, 2002; Zentall, Galizio, & Critchfield, 2002). The study of emergent relating behavior experienced a behavior-analytic renaissance, of sorts, in the 1970s when Murray Sidman dropped everything else and began publishing studies on what would come to be called stimulus equivalence (Sidman, 1971; Sidman & Cresson, 1973; Sidman, Cresson, & WillsonMorris, 1974). As most readers know, stimuli are related as equivalent when following If A Then B and If A Then C training, the individual, without further training, demonstrates that A1⁄4A, B1⁄4B, C1⁄4C, B1⁄4A, C1⁄4A, B1⁄4C, and C1⁄4B, typically in a conditional discrimination task where the first symbol serves as a sample stimulus and the second is selected from several available comparison stimuli (Sidman & Tailby, 1982). Substituting a dog for Stimulus A, “dog” for B, and “perro” for C, reveals why this research paradigm was quickly recognized as a means by which a behavior-analytic approach might be applied to the study of complex cognitive phenomena (e.g., Fields, Verhave, & Fath, 1984; Sidman, 1986). That is, an approach focused on identifying the necessary and sufficient conditions for producing emergent relating behavior. This special issue of the Journal of the Experimental Analysis of Behavior (JEAB) focuses on stimulus–stimulus relations. Understanding the varieties of relating behavior has generated an enormous amount of research in human and animal laboratories and the findings have generated new theories that have themselves occasioned additional investigations. As has so often been the case in our science, translational research findings have emerged and, in some circles, have proliferated. This special issue of JEAB offers an opportunity to look back upon what we know, what we are learning today, and to consider the ongoing potential of what has proven to be a fruitful research line. In what follows of this editorial, we walk that path.