Similar consumption and responding across single and multiple sources of drug

Two experiments were conducted to assess whether total response output and total consumption would be similar when drugs are available from single and multiple sources of reinforcement, as predicted by behavioral economics. In Experiment 1, cigarette-deprived smokers were exposed to a concurrent-chains schedule in which equal fixed-ratio schedules served as the initial links, and different reinforcer magnitudes (i.e., number of cigarette puffs) were arranged across alternatives. After the session, obtained unit price was calculated and imposed in the next session when a different number of puffs was available according to a single fixed-ratio schedule. Thus, the unit price at which cigarette puffs could be earned was yoked within subjects across the single and concurrent-chains schedules. When plotted as a function of unit price, similar consumption and response rates were usually obtained across these schedules. Experiment 2 addressed a weakness of Experiment 1, namely, that responding was allocated exclusively to the larger reinforcer magnitude in concurrent-chains conditions, and therefore this schedule may have functioned as a single schedule. In Experiment 2, subjects were instructed to alternate responding between the two alternative schedules. Instructions produced approximately equal response allocation between the two alternatives. Again, similar consumption and response rates were observed across the single and instructed concurrent-chains schedules. These findings are discussed in the context of direct effects and behavioral economics perspectives of drug self-administration.     

Slowing of memory-search performance in men with mild hypertension

Previous reports have associated hypertension with a slowing of cognitive performance, although the component processes involved have not been identified. Our report compares the performance of 24 men with mild hypertension and 28 age-matched normotensive men on a test of short-term memory search in which the duration of component processes could be estimated. The results indicated that the rate of search through short-term memory was slower for the hypertensive than for the normotensives, whereas the duration of encoding and response processes was equivalent for the two groups. This hypertension-related slowing of memory comparison was independent of participants' error rates and education levels.     

Units of interaction, evolution, and replication: organic and behavioral parallels

Organic and behavioral evolution both involve variation, selection, and replication with retention; but the individuals involved in these processes differ in the two kinds of evolution. In this paper, biological units of evolution, selection, and retention are compared with analogous units at the behavioral level. In organic evolution, natural selection operates on variations among organisms within a species, with the result of preserving in future generations of organisms those heritable characteristics that contributed to the organism's survival and reproduction. Species evolve as characteristics of the population change as a result of past selection. Continuity in a lineage in the biosphere is maintained by replication of genes with retention of organismic characteristics across successive generations of organisms. In behavioral evolution, reinforcement operates on variations among responses within an operant, with the result of preserving in future responses those characteristics that resulted in reinforcement. Continuity in a behavioral lineage, within the repertoire of a given organism, appears to involve retention and replication, but the unit of retention and replication is unknown. We suggest that the locus of retention and replication is the nervous system of the behaving organism.     

Response learning confounds assays of inhibitory control on detour tasks

Animal Cognition - The ability to inhibit prepotent actions towards rewards that are made inaccessible by transparent barriers has been considered to reflect capacities for inhibitory control (IC)....     

Three predictions of the economic concept of unit price in a choice context

Economic theory makes three predictions about consumption and response output in a choice situation: (a) When plotted on logarithmic coordinates, total consumption (i.e., summed across concurrent sources of reinforcement) should be a positively decelerating function, and total response output should be a bitonic function of unit price increases; (b) total consumption and response output should be determined by the value of the unit price ratio, independent of its cost and benefit components; and (c) when a reinforcer is available at the same unit price across all sources of reinforcement, consumption should be equal between these sources. These predictions were assessed in human cigarette smokers who earned cigarette puffs in a two-choice situation at a range of unit prices. In some sessions, smokers chose between different amounts of puffs, both available at identical unit prices. Individual subjects' data supported the first two predictions but failed to support the third. Instead, at low unit prices, the relatively larger reinforcer (and larger response requirement) was preferred, whereas at high unit prices, the smaller reinforcer (and smaller response requirement) was preferred. An expansion of unit price is proposed in which handling costs and the discounted value of reinforcers available according to ratio schedules are incorporated.     

Cross-modal, auditory-visual Stroop interference: a reply to Cowan and Barron (1987)

This series of experiments was performed to verify Cowan and Barron's (1987) reported effect of auditory color-word interference on a visual Stroop task. Extant theory predicts effects of irrelevant speech on visual memory tasks involving immediate, ordered recall of the items. Interference between the two sources of information (visual and auditory) is assumed to be located at the phonological store component of the articulatory loop. Perceptual tasks such as the Stroop task, which do not require use of the articulatory loop for rehearsal purposes, should not be similarly susceptible. The present data fail to replicate Cowan and Barron's findings, and are thus consistent with contemporary theory.     

Making sense of sensitivity in the human operant literature

Human operant behavior is often said to be controlled by different variables or governed by different processes than nonhuman operant behavior. Support for this claim within the operant literature comes from data suggesting that human behavior is often insensitive to schedules of reinforcement to which nonhuman behavior has been sensitive. The data that evoke the use of the terms sensitivity and insensitivity, however, result from both between-species and within-subject comparisons. We argue that because sensitivity is synonymous with experimental control, conclusions about sensitivity are best demonstrated through within-subject comparisons. Further, we argue that even when sensitivity is assessed using within-subject comparisons of performance on different schedules of reinforcement, procedural differences between studies of different species may affect schedule performance in important ways. We extend this argument to age differences as well. We conclude that differences across populations are an occasion for more precise experimental analyses and that it is premature to conclude that human behavior is controlled by different processes than nonhuman behavior.     

GENETIC AND ENVIRONMENTAL CONTRIBUTIONS TO VARIANCE IN AGE AT FIRST SEXUAL INTERCOURSE

Abstract— Little is known about the relative importance of genetic and environmental factors as determinants of age at first sexual intercourse. In this study, subjects were 5,080 individuals from the Australian Twin Registry (3,310 females, 1,770 males, age range 27–70 years, median 40 years) who completed a semistructured interview by telephone in 1992–1993. Self-reported age at first intercourse correlated higher for identical (monozygotic) twins than for nonidentical (dizygotic) twins. Structural equation model fitting found that the genetic contribution to variance was considerably greater among twins aged 40 years or less (72% for males and 49% for females) than for those aged from 41 to 70 years (0% for males and 32% for females). Among the older cohort, there was evidence that somewhat different aspects of the shared social environment influenced age at onset in males and females. In a more laissez-faire social climate in recent decades, it is likely that biological and psychological characteristics that are partly under genetic control significantly influence the age at which a person commences sexual activity.