Conditioned vocalization in rats.

Abstract

Attempts to condition vocalization in the rat have produced inconsistent results. These inconsistencies might be understood in terms of two crucial variables: the mobility of the subject during conditioning and the variability of the intertrial interval. New research is reported which directly examines the effects of these two variables and supports the importance of immobilizing the subject, but not of varying the intertrial interval during conditioning. It is suggested that vocal behavior in the rat may be conditioned only when no competing species-specific defense reaction (e.g., freezing) is available to the subject. The first attempt to condition shockelicited vocalization in rats was reported in 1932. During the ensuing 40 years, reports have appeared indicating that rat vocal behavior is both easily conditioned and impossible to condition. The present paper attempts to reconcile some of these contradictory results by reference to key procedural differences in these studies. In uncovering which variables are crucial to the vocal conditioning process, it is hoped that a more comprehensive view of vocal behavior in the rat will emerge. Warner (1932) reported sporadic instances of what looked like conditioned vocalizations to shock in one rat. Following this lead, Schlosberg (1934) exposed rats to signal-shock pairings in a Pavlovian conditioning procedure with light or buzzer serving as the conditioned stimulus (CS) and shock as the unconditioned stimulus (US). Variable intertrial intervals (ITIs) regulated stimulus presentations, and all subjects were immobilized in an inverted cage which fit over them like a lid. Schlosberg reported a reliable conditioned vocal response (CR) in his subjects. Almost a decade later, Cowles and Pennington (1943) used a conditioned vocal re1JThe authors are grateful to Annette Ehrlich, David Perrott, E. D. Bailey, Veronika Coltheart, and Harry M. B. Hurwitz for their critical assistance. This paper is dedicated to Juarez, a responsible mouse.