10 albino rats were divided into 2 groups and were exposed to a DRL-18-sec. schedule. For one group a block of wood was present for the first 40 days while for the second group no wood was present. Subjects with wood available initially showed more reinforced barpresses primarily due to long interresponse time responses (27+ sec.) and large amounts of collateral wood chewing. After 28 days the two groups were receiving essentially the same number of reinforcements. After 40 days the conditions of wood availability were reversed. The animals with wood now available did not engage in collateral wood chewing, and there was no apparent difference in the performance of the two groups. The results question the hypothesis that collateral activities serve as time-mediational devices.
Data from a previously reported study were re-analyzed to determine whether increased cautiousness could explain age differences in performance requiring selective attention. 175 female volunteers, ranging in age from 17 to 72 yr., were given an auditory task requiring selective attention. An intrusion-to-omission ratio, computed for each subject, showed no significant differences across the age range. Results indicate increased cautiousness on the part of elderly persons cannot adequately explain age differences in performance requiring selective attention.
Following acquisition of an instrumental avoidance response, 36 preschool Ss were given 200 extinction trials. Omission of children's songs served as the aversive event. Three extinction procedures were established: (a) a CS-only procedure in which the music was never omitted, (b) Ii punishment procedure in which music omission was response contingent, and (c) a procedure whereby music omission was unavoidable and inescapable. The results were dependent upon the extinction procedures being compared; however, the CS-only procedure was most resistant to ex tinction. The most commonly used procedure for extinguishing avoidance responses consists of presenting the warning signal (CS) while withholding the aversive stimulus (US) which had been associated with it during acquisition. However, Davenport and Olson (1968) argued that a more appropriate procedure would be to make the US unavoidable and the CS inescapable until the US occurred , since the reinforcing event in acquiring an avoidance response is presumed to be the escape of the CS and/or omission of the US. Using this procedure, Davenport and Olson (1968) reported rapid and reliable decreases in avoidance responding in rats. Hartley (1968) compared two unavoidable and inescapable US procedures (UI) with the typical CS-only extinction procedure in rats. No significant differences were reported between the two UI procedures. Ss in both UI groups extinguished significantly faster than Ss in the CS-only group. Bolles, Moot, and Grossen (I 971) investigated CS-only, punishment, and two UI procedures in the ex tinction of shu ttIebox avoidance in rats. Extinction occurred most readily when Ss acquired an effective alternative response to avoid shock (Le., punishment). When all behaviors avoided shock (i.e., CS-only), avoidance was extremely resistant to extinction. When Ss continued to receive unavoidable shock (Le ., VI procedures) avoidance responding felI to a level intermediate between the two other procedures. Research comparing various extinction of avoidance responding in human Ss has not been extensive. Meyer (1970) investigated CS-only, punishment, and two UI extinction procedures in co lIege Ss. A 6-sec-duration, 40-psi air blast behind the right ear served as the US. Meyer (1970) stated that the CS-only was the least effective and punishment was most effective in *Reprint requests should be sent to the first author,
8 female albino rats were divided into 2 groups that were exposed to a DRL 18-sec. schedule. One group had water available for the first 30 days while the second did not. Ss with water available initially showed more reinforced bar presses but by the end of the second week rats with no water available demonstrated superior performance. After the initial 30 days the conditions of availability of water were reversed. The animals with water available consistently received fewer reinforcements for the remaining 28 days of the experiment. Also, they consumed far less water than did the group which had water available during the initial 30 days. The results are discussed in terms of schedule-induced polydipsia.
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