COMBINED‐STIMULUS CONTROL AS A FUNCTION OF THE RESPONSE RATE CONTROLLED BY THE ABSENCE OF THE SINGLE STIMULI¹

Abstract

Rat's bar-press responses were maintained at moderate rates during separate presentations of light and tone by separate but concurrent variable-interval schedules of food and shock presentation. The relative response rate maintained during light-out-no-tone was alternated in four successive phases: in Phases 1 and 3 responding was maintained at a higher rate than that during light and tone alone by a variable-interval food schedule, while in Phases 2 and 4 responding was reduced to a lower rate by a differential-reinforcement-of-otherbehavior food schedule. In test presentations of light, tone and a light-plus-tone combination, administered at the end of each phase, the proportion of responses emitted during light-plus-tone was an inverse function of the relative response rate controlled by light-outno-tone, indicating that the relative training response rate controlled by the absence of the single stimuli determined the control exerted by the combined stimuli. Different relative response rates maintained in training may also be partly responsible for previously observed differences in the form of generalization gradients following the establishment of multistimulus control.When responding is conditioned during each of two single stimuli, the combination of both stimuli frequently controls either a higher (Emurian and Weiss, 1972;Meltzer and Freeman, 1971; Miller, 1969bMiller, , 1971Riess, 1969;Wolf, 1963) or a lower (Miller, 1969a;Reberg and Black, 1969;Van Houten and Rudolph, 1971) response rate than either single stimulus. While the variables responsible for these seemingly discrepant findings remain unclear, it has been pointed out (Weiss and Emurian, 1970) that one procedural variable common to all of the studies may account for the different results. In all of the studies, a third stimulus condition, consisting of a period during which both single stimuli were simultaneously absent, was included in training along with the single-stimulus conditions. In the studies reporting a higher response rate during the combined stimuli, this period controlled a lower response rate than either single stimulus, while in studies reporting a lower re-1I thank Susan Levine, Daniel Dinsmoor, and Dr. Michael D. Zeiler for substantial contributions concerning the present manuscript, which was prepared at the American University and supported in part by Grant MH-16853 to S. J. Weiss. A portion of this research was reported at the Eastern Psychological Association meeting in Boston, April, 1972. Reprints may be obtained from the author, Psychology Department, Bradley University, Peoria, Illinois 61606. sponse rate during the combined stimuli, this period controlled a higher response rate than either single stimulus. Thus, the response rate controlled by the absence of both single stimuli, relative to that controlled by the presence of each single stimulus, was different in studies reporting higher versus lower response rates during the combined stimuli. The present experiment examined the possibility that this difference influe...

DISCRIMINATED RESPONSE AND INCENTIVE PROCESSES IN OPERANT CONDITIONING: A TWO‐FACTOR MODEL OF STIMULUS CONTROL1

“…This comparability includes methods of training and testing (see Weiss, 1972, p. 205). 'Wiltz (1974) reported additive summation during stimulus compounding after training on a baseline similar to that used by Wiltz (1972), where summation was not obtained. This could be due in part to the different conditioning histories in T+L between experiments.…”

“…punishment Wiltz, 1972). In both cases, where responding was maintained by positive reinforcement in all components, T+L would be preferred to tone and light, which were also shock associated (Hearst and Sidman, 1961).…”

“…cSee Footnote 2 (page 368) for a methodological analysis of the studies reported by Wiltz (1972Wiltz ( , 1974.…”

COMBINING STIMULI SIGNALLING RESPONSE‐DEPENDENT FOOD AND SHOCK1

“…On the other hand, when behavior that is at a high level during the absence of two single stimuli is decreased by response-dependent shock delivery during the presence of each of the single stimuli, it decreases further when the single stimuli are combined (Miller, 1969;Reberg and Black, 1969;Van Houten and Rudolph, 1971;Wiltz, 1972).…”

“…Furthermore, combined shock-associated stimuli also fail to enhance suppression when the absence of both single stimuli controls low levels of behavior after having previously controlled high levels of behavior (Wiltz, 1972). Finally, combined stimuli signalling only food delivery suppress behavior to a greater extent than the single stimuli when the absence of both stimuli controls the highest level of behavior in the training schedule (Howerton, 1972).…”