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JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOREFFECTS OF dl-AMPHETAMINE UNDER CONCURRENTVI DRL REINFORCEMENTEVALYN F. SEGAL1WALTER REED ARMY INSTITUTE OF RESEARCH ANDLABORATORY OF PSYCHOPHARMACOLOGY, UNIVERSITY OF MARYLAND2Three adult, food-deprived rats were given IP injections of dl-amphetamine sulfate underDRL and concurrent VI DRL reinforcement schedules. The drug results were as follows.(1) The IRT distributions of DRL responses shifted to the left, but some temporal dis-crimination remained. (2) The IRT distributions of VI responses shifted slightly to the left.(3) The distinguishing characteristics of VI and DRL IRT distributions were preserved.(4) The frequency distribution of number of VI responses between two consecutive DRLresponses was relatively unaffected. (5) Over-all response rates on the two components of theconcurrent schedules increased more or less proportionately.These findings imply that the primary behavioral effect of dl-amphetamine was a motorexcitatory one. The drug's disruption of timing behavior was not due to a derangement ofinternal timing mechanisms, nor to interference with the topography or pattern of behavior.Rather, it might be a secondary result of the accelerated emission of overt behavior patternsmediating the temporal spacing of DRL bar presses.Several reviews of psychopharmacologicalresearch on the amphetamines have appearedwithin recent years (Brady, 1957; Dews &Morse, 1961; Owen, 1960; Sidman, 1959).From these reviews and the supporting data,some principles of amphetamine action aregradually emerging that promise to unify thevast and paradoxical body of amphetaminefindings. The following are among the princi-ples with the best experimental support. (1)Amphetamine reduces food and water con-sumption (Dews & Morse, 1961) and possiblysome vague entity called "appetite" (Owen,1960). (2) In carefully circumscribed condi-tions, amphetamine increases the total amountof "spontaneous activity" (Dews & Morse,1961). (3) Amphetamine enhances "condi-tioned emotionality,"3 especially aversively1This research was completed during the writer'stenure of a Postdoctoral Research Fellowship from theNational Institute of Neurological Diseases and Blind-ness, under the sponsorship of Dr. J. V. Brady. Thanksare due to the Laboratory of Psychopharmacology ofthe University of Maryland for provision of some ofthe research facilities under Grant No. MY-1604 fromthe National Institute of Mental Health, and to Mr.C. R. Schuster for advice and assistance in the conductof the experiment.'Present address: San Diego State College."Dews and Morse (1961) think that the evidence onthis point is no more than 'suggestive; nonetheless, ithas sufficient experimental support to qualify as apromising integrative principle.aroused emotionality (Brady, 1957; Teitel-baum & Derks, 1958) and "post-drug depres-sion" (Verhave, 1958), but perhaps also "eu-phoric" types of emotion (Dews & Morse, 1961;Miller, 1956, 1957). (4) Amphetamine differ-entially affects behavior maintained by differ-ent reinforcement schedules (Dews & Morse,1961) and by different parameters of a givenschedule (Dews, 1960). (5) Amphetamine in-fluences rates of responding both by shorten-ing long (5 sec or more) IRT's and lengthen-ing short (less than 1 sec) IRT's (Dews, 1958;Dews & Morse, 1961; Morse & Herrnstein,1956).Another finding, which is not so well con-firmed as those above but yet is mentioned inthe experimental literature, is that appropri-ate doses of amphetamine affect discriminativebehavior. Apparently, simple discriminationsare not affected (Dews, 1955; Sidman, 1956a,1956b), but complex "conditional" discrimina-tions are (Dews, 1955). Moreover, impairmentof "sensory responsiveness" or "attentiveness"is suggested by failure to respond to stimulisignalling the brief availability of food(Teitelbaum & Derks, 1958; Weissman, 1959).The failure of food consumption may, ofcourse, be interpreted simply as a consequenceof reduced "hunger." However, as Teitelbaumand Derks (1958) contend, and this writerconcurs, animals under amphetamine often105VOLUME 5, NUMBERIJANUARY, 1 962