An alternative to the operant-response-based CER procedure is described in which suppression of licking behavior in rats provided a measure of the CER. The results indicated that acquisition and resistance to extinction of conditioned suppression of licking varied directly with the intensity of shock used during training. These Fmdings were discussed in relation to similar results reported for conditioned suppression of operant behavior.Conditioned suppression oflever pressing is a well-established procedure for studying the principles of emotional conditioning (cf. Beecroft, 1967, pp. SO-53). First utilized by Estes & Skinner (1941) and subsequently standardized by Kamin and his associates (e.g., Annau & Kamin, 1961), this procedure involves the conditioning of an emotional response (fear) by pairing shock with some neutral stimulus. In the experiments by Kamin, rats are reinforced for lever pressing on a VI 2.5-min schedule during 2-h daily sessions. After operant response rate has stabilized, four trials of CS-shock pairings are presented each day. Since the conditioned emotional response (CER) is assumed to be incompatible with operant responding, the extent to which the Ss refrain from lever pressing during the 3-min CS will provide a measure of the CER.In the present experiment, instead of using ongoing operant behavior as a base against which the CER is superimposed, acquisition and extinction of the emotional response occurred against a background of consummatory responding, i.e., licking. Although Leaf & Muller (1965) have used suppression of licking as an indicator of the strength of a CER acquired in a nonlicking situation, their procedure is limited to providing a one-trial test. The present study is analogous to the Kamin procedure in that it provides a trial by trial measure of CER.Annau & Kamin (1961) have reported that acquisition and resistance to extinction of an operant-response-based CER are increasing functions of UCS intensity. In the present experiment it was expected that by varying shock intensity, similar functions would be obtained for a consummatory-response-based CER. METHOD Subjects The Ss were 32 male Holtzman albino rats, either 250 days of age and previously used in a runway study (N = 16) or 90 days of age and experimentally naive (N = 16). The Ss from each age group were equally represented in each of the shock·intensity conditions. Apparatus A modified commercially manufactured conditioning chamber (Scientific Prototype A·1oo), with the manipulandum and food cup removed, was set in a ventilated, sound-insulated box (Lehigh Valley A·64). Clear Plexiglas windows at the front (3 x 5 in.) and rear (6 x 6 in.) replaced portions of the metal walls. Two 6·W, 120·V ac incandescent lamps were mounted behind the front windows 6 in. above the grid floor and served as one component of the compound CS. The other component of the CS, white noise of 82 dB, was produced by means of a Grason-Stadler 901B noise generator. Continuous illumination was provided by one 6-W, 12O-Vac lamp located 4 i...

Two experiments tested the hypothesis that the decremental effects of massed practice are due to the development of a negative drive (Hull's Ir). The results indicated that the decremental effects of massed practice on either the pursuit rotor or the two-hand coordinator do not transfer to depress performance or reminiscence on the other task. The results did not support Hull's drive interpretation but were explained by theories attributing decrement to a decreased level of arousal.

Two groups of 12 rats received extensive lever-pressing-discrimination training to 4 intensities of auditory stimulation (85, 90, 95, 100 db); one intensity was SA and three were S D . For one group, the lowest intensity stimulus was non-reinforced; for the other group the highest intensity stimulus was die S A . After 24 days, non-reinforcement in each group was switched to stimulation of the other extreme and performance was assessed for an additional 15 days. Results indicated: (a) that during the first phase response strength was a positive function of the distance, along the intensity continuum, from the non-reinforced stimulus, (b) that after non-reinforcement contingencies were changed, performance was immediately disrupted and tended to be replaced by the functional relation of the initial phase, and (e) that S A response rate was positively related to S A intensity. THE POSITIVE RELATION BETWEEN stimulus intensity and response strength,termed stimulus intensity dynamism (sm), has been interpreted in a number of ways. Although Hull (1952) assigned sn> to the role of a primary molar law, other investigators have conceptualized it in terms of stimulus generalization (Perkins, 1953;Logan, 1954), adaptation level (Grice & Hunter, 1964 ), and decision models (Grice, 1968 ).The Perkins-Logan hypothesis, that sro results from inhibition which generalizes from a non-reinforced zero-intensity background stimulus, was supported in two studies reported by Gray. One investigation (Gray, 1965a) indicated that in an instrumental conditioning situation, discrimination training is necessary to generate sro. Although unpublished, a second study was referred to in a review article of sro (Gray, 1965b, Footnote 4, p. 185). It indicated that a negative relation between discriminative stimulus (S D ) intensity and response rate during each S D was produced in rats reinforced for responding in the presence of white noise varying in intensity from 0 to 90 db but never reinforced in the presence of a 100 db noise. Similar evidence was recently obtained in a discriminated lever-press avoidance situation (Birkimer & James, 1967). When shock never followed

In four studies, with rats as Ss, acquisition and. where appropriate.~\ tinction trials were presented against a baseline of ongoing licking. At shock intensities of 0.1. 0.5. 1.0, or 2.0 mA, acquisition performance was a function of number of CS-DS pairings; spacing of trials (one or two per day) did not affect acquisition performance. Resistance to extinction could be predicted from terminal acquisition performance and reached a maximum after three CS-lIS pairings.

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