Abstract. Four rats were trained to barpress for water reinforcement under a variable interval 60 sec schedule. 1XTine acute administrations of (--)Ag-trans-tetrahydrocannabinol, in amounts ranging from 0.25 to 16.0 mg/kg, produced doserelated effects on responding; overall response rate increased at lower doses, while higher doses produced ataxia and a complete suppression of responding. Increased response rates reflected changes both in response spacing and in the lengths of postreinforcement pauses. It was concluded that marihuana has a biphasic effect on variable interval water-reinforced behavior in rats. Key words: Marihuana (Cannabis) --(--)39-trans-Tetrahydrocannabinol(Ag-TttC) --Psychopharmacology --Operant Behavior --Schedule of Reinforcement.Both the unconditioned behavior and conditioned shock avoidance behavior of animals have been shown to be either increased or decreased by marihuana or a tetrahydroeannabinol (THC) derivative (e.g., Barry and Kubena, 1971 ; Garriott, King, Forney and Hughes, 1967;Holtzman, Lovell, Jaffe and Freedman, 1969;Kubena and Barry, 1970; Seheckel, Boff, Dahlen and Smart, 1968). A greater consistency between findings has been obtained with simple appetitive reinforcement operant conditioning schedules where the usual effect of marihuana has been to suppress the ongoing rate of response in rats and pigeons (e.g
Pigeons' choice responding on 10-sec interpolated probes was studied after baseline training on multiple variable-interval variable-interval schedules of food reinforcement. Unreinforced choice following training with three different relative reinforcement rates (Experiment 1), with a 3-ply multiple schedule (Experiment 2), and with three different relative reinforcement durations (Experiment 3) was examined. Least squares lines were fit to choice relative response rate and schedule relative response rate as functions of training relative reinforcement rate; choice slope was significantly greater than schedule slope in all three experiments. This result is counter to the prediction of Herrnstein's (1970) theory that these slopes should not differ. Lues's (l959l theory also failed to account for the data. It was concluded that choice responding was controlled by both approach to the stimulus associated with the smaller mean interreinforcerinterval or the longer duration, and avoidance of the other stimulus.Herrnstein's (1970) theory specifies the relation between response strength and reinforcement rate in the components of multiple and concurrent schedules. Since Herrnstein further proposes that "choice is nothing but behavior set into the context of other behavior" (p. 255), relative response frequency should be the same whether measured simultaneously or successively, once component response strengths are established by the schedule. That is, Herrnstein's equation for multiple-schedule relative response frequency is also the equation for choice relative response frequency following multiple-schedule training. This prediction, that schedule and choice relative rates should be equivalent functions of reinforcement, was evaluated by investigating choice responding on interpolated probes following asymptotic multiple-schedule training.The choice probe results also permit further evaluation of the applicability of Luce's (1959) choice model in extinction tests. Luce (1977) has noted that matching on concurrent schedules is consistent with his model. However, Herrnstein and Loveland (1976), who employed a transfer test similar to that used here, found that choice results were more extreme than predicted by Luce's model. Herrnstein and Loveland (1976) employed this scale in predicting choice. The question of interest here is whether or not the model applies when choice is predicted by a scale derived from previous choice tests, not schedule responding. If the theory applies in this situation, we would have a basis for a ratio scale of relative response strength as a function of relative reinforcement rate for multipleschedule training, which is what the matching law provides for concurrent-schedule training. Nevin (1974) has reviewed arguments for the desirability of such a scale, with response strength conceived as a psychological construct that varies with parameters of reinforcement.Experiment 1 studied choice following three different relative reinforcement rates. To extend the generality of the results and...
A digital interface to support the SKED software system in recent versions of the PDP-8 computer. One printed circuit card of interface logic and optical isolators can be installed in the OMNIBUS to provide 24 input and 36 output lines to external panels containing input simulation switches and input or output indicators.
Three experiments investigated stimulus control of key pecking in pigeons by varying the distance of vertices movement for a six-point complex visual shape. Ease of discrimination learning was monotonically related to the distance of vertices movement when the directions of vertices movement were held constant. As suggested by selective attention theory, steep generalization gradients were obtained following intradimensional differential training but not following nondifferential training or interdimensional differential training. These results indicate that, unlike the dimension of angular orientation or tilt, distance of vertices movement provides a consistent functional representation of complex shape similarity.
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