Cocaine tolerance: acute versus chronic effects as dependent upon fixed-ratio size.

The effects of cocaine on operant behavior were studied by examining fixed-ratio value as a factor in the development of tolerance. Pigeons pecked a response key under a three-component multiple schedule, with each bird being exposed to fixed-ratio values that were categorized as small, medium, or large. Administered acutely, cocaine (1.0 to 10.0 mg/kg) produced dose-related decreases in overall rate of responding. Responding maintained by the largest ratio was decreased by lower doses than those required to reduce rates of responding maintained by the other two ratio schedules. Following repeated daily administration of 5.6 mg/kg of cocaine, dose-effect functions (obtained from sessions during the chronic regimen by making substitutions for the daily dose) indicated tolerance under the smaller ratios, but no tolerance or less tolerance under the largest ratio. Thus, whether tolerance developed, and the degree to which it developed, depended on the ratio value. The results are partially consistent with the notion that tolerance to drug effects on schedule-controlled behavior will develop if drug administration initially reduces reinforcement frequency, but they indicate that reinforcement loss alone is not a sufficient condition for the generation of tolerance under such conditions. The findings suggest that amount of responding required for reinforcement, or "effort," may contribute to the development of tolerance to effects of cocaine.     

Read but not write “Idea”: Evidence for a third reading mechanism

Most information processing accounts of reading incorporate either two or three mechanisms by which oral reading may be accomplished. The existence of a “third” mechanism by which words may be read lexically but without semantic mediation remains controversial. We report data from a patient (W.T.) with an infarction involving Wernicke's area who was unable to write, repeat, or comprehend words of low imageability yet read these and other words reliably; the patient could not, however, read nonwords. As the patient was unable to read on the basis of sublexical print-to-sound correspondences and, at least for words of low imageability, was unable to read by means of a semantically mediated process, the data from this patient are most readily accommodated by models of reading incorporating three mechanisms.     

Effects of variable-interval value and amount of training on stimulus generalization.

In Experiment 1 pigeons pecked a key that was illuminated with a 501-nm light and obtained food by doing so according to a variable-interval (VI) schedule of reinforcement, the mean value of which differed across groups: either 30 s, 120 s, or 240 s. The pigeons in all three groups were trained for 10 50-min sessions. Generalization testing was conducted in extinction with different wavelengths of light. Absolute and relative generalization gradients were similar in shape for the three groups. Experiment 2 was a systematic replication of Experiment 1 using line orientation as the stimulus dimension and a mean VI value of either 30 s or 240 s. Again, gradients of generalization were similar for the two groups. In Experiment 3 pigeons pecked a key that was illuminated with a 501-nm light and obtained food reinforcers according to either a VI 30-s or a 240-s schedule. Training continued until response rates stabilized (> 30 sessions). For subjects trained with the 30-s schedule, generalization gradients were virtually identical regardless of whether training was for 10 sessions (Experiment 1) or until response rates stabilized. For subjects trained with the VI 240-s schedule, absolute generalization gradients for subjects trained to stability were displaced upward relative to gradients for subjects trained for only 10 sessions (Experiment 1), and relative generalization gradients were slightly flatter. These results indicate that the shape of a generalization gradient does not necessarily depend on the rate of reinforcement during 10-session single-stimulus training but that the effects of prolonged training on stimulus generalization may be schedule dependent.     

Review of William Paley, <Emphasis Type="Italic">Natural Theology</Emphasis>, edited with an introduction and notes by Matthew D. Eddy and David Knight

Matthew D. Eddy and David Knight’s new edition of William Paley’s Natural Theology deserves to become the standard scholarly edition of what is a historically, theologically, and philosophically important work, despite a certain neglect of philosophical issues on the part of the editors.     

Titrating-delay matching-to-sample in the pigeon

The titrating-delay matching-to-sample (TDMTS) procedure offers researchers an additional behavioral task thought to capture some important features of remembering. In this procedure, the delay between sample offset and comparison onset adjusts as a function of the subject's performance. Specifically, correct matches increase the delay and incorrect matches decrease the delay, and steady-state titrated delays serve as the primary dependent measure. The present series of experiments investigated the effects of several procedural variables on performance in TDMTS procedures in an effort to elucidate better its features to allow for more precision in future use. Experiment 1 reports results from a parametric analysis of fixed-ratio response requirements on the sample key that indicated improved remembering in the form of higher daily titrated delay values as the requirement was increased. Experiment 2 investigated the extent to which the initial delay value in each session affected session-wide delay values. Results indicated that regardless of value of the initial delay, the subjects' performances adjusted the delay values in the direction of the known baseline delay-value levels. Experiment 3 manipulated the step size by which delay values were adjusted and the results indicated that larger step sizes increased both session-to-session variability and within-session range of titrated delay values, although the average values remained approximately the same. These results suggest that the TDMTS task serves as a promising procedure to study what many refer to as memory.     

Religion and the Survival of 1010 Hospitalized Veterans

Objective: To examine the effects of religious affiliation and religious coping on survival of acutely-hospitalized medically-ill male veterans following discharge. Sample and Methods: Between 1987 and 1989, comprehensive psychosocial and physical-health evaluations were performed on a consecutive sample of 1010 patients ages 20–39 and 65–102 years admitted to the general medicine and neurology services of the Veterans Administration (VA) Medical Center in Durham, North Carolina. Religious affiliation and religious coping (the degree to which a patient relied on his religious faith for comfort and strength) were among the variables assessed. Subjects or surviving family members were contacted by telephone in 1996–97 to determine vital status; dates of death were confirmed by the Veterans Administration's Beneficiary Identification and Records Locator Subsystem (BIRLS), death certificate, or the National Death Index. Cox proportional-hazards regression was used to model the effects of religious variables on time to death, controlling for demographic, social, psychiatric, and physical-health covariates. Results: Follow-up was obtained on all 1010 patients. During the observation period, 673 patients died. While a higher proportion of conservative Protestants than members of other religious groups died during this time (70.5% vs. 64.3%, p = .04), the association disappeared once covariates were controlled. Religious coping was unrelated to survival in both bivariate and multivariate analyses (hazard ratio 1.00, 95% CI 0.99–1.01). Conclusions: Neither religious affiliation nor dependence on religion as a coping behavior predicted survival in this sample of medically-ill male veterans. Several reasons for the absence of an effect are explored, notably the fact that the mortality force exerted by age, medical diagnosis, and severity of physical-health problems overwhelmed the weaker effects of psychosocial variables.     

Key pecking during extinction after intermittent or continuous reinforcement as a function of the number of reinforcers delivered during training.

Key pecking by 7 pigeons was established and maintained on a multiple variable-ratio variable-ratio (VR) schedule of food presentation. The schedule in one of the components was then changed to fixed-ratio (FR) 1 for a predetermined number of reinforcers. Both components were then changed to extinction (i.e., multiple extinction, extinction). This sequence was repeated a different number of times for each pigeon to determine the relation between the number of reinforcers delivered during each component of the multiple VR FR 1 schedule and the number of responses during extinction. For most pigeons, there were fewer responses during extinction in the presence of a stimulus recently correlated with FR 1, regardless of the number of reinforcers received. The ratio of the total responses in extinction in the former VR component to the total responses in the former FR 1 component increased as the number of reinforcers delivered during each component of the multiple schedule increased. Within-subject replications of the partial-reinforcement extinction effect generally occurred, and there were no overall reductions in the number of responses in extinction with repeated exposures to extinction.     

Repeated post- or presession cocaine administration: roles of dose and fixed-ratio schedule

Effects of repeated administration of cocaine to animals behaving under operant contingencies have depended on when the drug is given. Moderate doses given presession have generally led to a decrease in the drug's effect, an outcome usually referred to as tolerance. When these same doses have been given after sessions, the usual result has been no change or an increase in the drug's effects, with the latter usually referred to as sensitization. In the present study, repeated postsession administration of a relatively small dose of cocaine (3.0 or 5.6 mg/kg) to pigeons responding under a multiple fixed-ratio 5, fixed-ratio 100 schedule of food presentation generally resulted in tolerance to the rate-decreasing effects of the drug. When the same dose was given before sessions, little additional tolerance was observed, although some subjects showed further tolerance in the small-ratio component. A regimen of repeated postsession injection of larger (10.0-23.0 mg/kg) doses suppressed key pecking during the session; responding resumed following discontinuation of postsession administrations. Effects of postsession administration of cocaine, therefore, depended on the dose, with smaller doses leading to tolerance and larger ones to suppression of behavior during the session. Effects of postsession drug administration of either small or large doses were not related to whether effects of postsession drug were experienced mainly in the operant test chamber or in the pigeon's home cage. The results with large postsession doses are compatible with a view that the drug acted as a Pavlovian unconditional stimulus, with the session-related stimuli acting as a long-duration Pavlovian conditional stimulus. Tolerance following postsession administration of the smaller doses challenges the view that it depended on experiencing the drug's effects while the arranged reinforcement contingencies were in effect.