Analysis of a guided-response procedure in visual discriminations by rats.

A guided-response procedure was used to train a visual pattern discrimination by rats in a modified Sutherland box. The method consisted of guiding the animal to the correct choice by means of a retractable bridge that led to reinforcers, followed by gradually removing this prompt. This method was compared to a stimulus-fading procedure, in which the initial differences between discriminative stimuli were gradually faded until they differed only with respect to the critical dimension for discrimination, and to a trial-and-error procedure. Both gradual procedures resulted in fewer errors compared to the trial-and-error procedure. The higher efficiency of the fading procedures was attributed to less aversiveness derived from performance with few errors and to the use of step-by-step requirements relative to the criterion performance.     

Pigeons' choices in situations of diminishing returns: fixed- versus progressive-ratio schedules.

In two different discrete-trial procedures, pigeons were faced with choices between fixed-ratio and progressive-ratio schedules. The latter schedules entail diminishing returns, a feature analogous to foraging situations in the wild. In the first condition (no reset), subjects chose between a progressive-ratio schedule that increased in increments of 20 throughout a session and a fixed-ratio schedule that was constant across blocks of sessions. The size of the fixed ratio was varied parametrically through an ascending and then a descending series. In the reset condition, the same fixed-ratio values were used, but each selection (and completion) of the fixed ratio reset the progressive-ratio schedule back to its minimal value. In the no-reset procedure, the pigeons tended to cease selecting the progressive ratio when it equaled or slightly exceeded the fixed-ratio value, whereas in reset, they chose the fixed ratio well in advance of that equality point. These results indicate sensitivity to molar as well as to molecular reinforcement rates, and those molar relationships are similar to predictions based on the marginal value theorem of optimal foraging theory (e.g., Charnov, 1976). However, although previous results with monkeys (Hineline & Sodetz, 1987) appeared to minimize responses per reinforcement, the present results corresponded more closely to predictions based on sums-of-reciprocals of distance from point of choice to each of the next four reinforcers. Results obtained by Hodos and Trumbule (1967) with chimpanzees in a similar procedure were intermediate between these two relationships. Variability of choices, as well as median choice points, differed between the reset and no-reset conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Choice in transition: A comparison of melioration and the kinetic model

Transition-state choice behavior of pigeons was examined in two experiments designed to test predictions of melioration and the kinetic model. Both experiments began with an initial training condition during which subjects were maintained on concurrent variable-interval schedules. In Experiment 1, subjects were then exposed to concurrent variable-ratio schedules, whereas in Experiment 2, subjects were then exposed to concurrent extinction. Contrary to the predictions of melioration, but consistent with the kinetic model, acquisition of preference on concurrent variable-ratio schedules followed a negatively accelerated logistic trajectory, and preference remained stable in concurrent extinction. Predictions made by the kinetic model concerning rates of switching between alternatives were also supported.     

Choice in the repeated-gambles experiment

Humans chose 10 times between two roulette wheels projected on a monitor. During the first trial, the left wheel provided a hypothetical $100 with p = .94, and the right wheel provided $250 with p = .39. A titration procedure adjusted the probability of a $250 win across trials to permit estimation of an indifference point between alternatives. In Experiment 1, intertrial-interval duration (25 vs. 90 s) and whether sessions began with an intertrial interval or a trial were varied in a 2 × 2 design in this risky-choice procedure. Risk aversion (preference for the $100 wheel) increased with intertrial interval but was unaffected by whether sessions began with a trial or an intertrial interval. In Experiment 2, all sessions began with a trial, and subjects were informed that the experiment ended after 10 trials. Intertrial-interval duration had no effect on choice. In Experiment 3, intertrial-interval duration and whether subjects were given $10 or $10,000 before beginning were varied among four groups in a 2 × 2 design. In all other ways, the procedure was unchanged from Experiment 2. Intertrial interval had no effect on choice, but the $10,000 groups showed less risk aversion than the $10 groups. These results can be explained more readily in terms of Kahneman and Tversky's (1984) notion of “framing of the prospect” than in terms of Rachlin, Logue, Gibbon, and Frankel's (1986) behavioral account of risky choice.     

Matching, delay-reduction, and maximizing models for choice in concurrent-chains schedules.

Models of choice in concurrent-chains schedules are derived from melioration, generalized matching, and optimization. The resulting models are compared with those based on Fantino's (1969, 1981) delay-reduction hypothesis. It is found that all models involve the delay reduction factors (T - t2L) and (T - t2R), where T is the expected time to primary reinforcement and t2L, t2R are the durations of the terminal links. In particular, in the case of equal initial links, the model derived from melioration coincides with Fantino's original model for full (reliable) reinforcement and with the model proposed by Spetch and Dunn (1987) for percentage (unreliable) reinforcement. In the general case of unequal initial links, the model derived from melioration differs from the revised model advanced by Squires and Fantino (1971) only in the factors affecting the delay-reduction terms (T - t2L) and (T - t2R). The models of choice obtained by minimizing the expected time to reinforcement depend on the type of feedback functions used. In particular, if power feedback functions are used, the optimization model coincides with that obtained from melioration.     

Responding on concurrent-chains schedules in open and closed economies.

Pigeons' key pecks were reinforced according to concurrent-chains schedules of reinforcement. The programmed average time from the onset of the initial links to a terminal link entry was held constant across conditions while the value of variable-interval schedules in the terminal links was varied. Performance was assessed under two economic conditions: (a) an open economy in which session duration was limited to 1 hr and subjects were maintained at 80% of their free-feeding body weights with postsession food when necessary; and (b) a closed economy in which sessions were 23.5 hr long and no deprivation regimen was in effect. In all cases, the relative rate of responding in the initial links matched the reduction in overall delay to primary reinforcement correlated with entry into one terminal link relative to the reduction in delay correlated with entry into the other terminal link. Although the sum of responses made in the initial links and terminal links was found to increase, then decrease, as the rate of food presentation decreased in the closed economy, there was no consistent effect of overall rate of food presentation on total responding in the open economy. The choice data suggest that relative delay reduction predicts choice accurately, regardless of economic context.     

Reinforcing effects of caffeine in coffee and capsules.

In a residential research ward the reinforcing and subjective effects of caffeine were studied under double-blind conditions in volunteer subjects with histories of heavy coffee drinking. In Experiment 1, 6 subjects had 13 opportunities each day to self-administer either a caffeine (100 mg) or a placebo capsule for periods of 14 to 61 days. All subjects developed a clear preference for caffeine, with intake of caffeine becoming relatively stable after preference had been attained. Preference for caffeine was demonstrated whether or not preference testing was preceded by a period of 10 to 37 days of caffeine abstinence, suggesting that a recent history of heavy caffeine intake (tolerance/dependence) was not a necessary condition for caffeine to function as a reinforcer. In Experiment 2, 6 subjects had 10 opportunities each day to self-administer a cup of coffee or (on different days) a capsule, dependent upon completing a work requirement that progressively increased and then decreased over days. Each day, one of four conditions was studied: caffeinated coffee (100 mg/cup), decaffeinated coffee, caffeine capsules (100 mg/capsule), or placebo capsules. Caffeinated coffee maintained the most self-administration, significantly higher than decaffeinated coffee and placebo capsules but not different from caffeine capsules. Both decaffeinated coffee and caffeine capsules were significantly higher than placebo capsules but not different from each other. In both experiments, subject ratings of "linking" of coffee or capsules covaried with the self-administration measures. These experiments provide the clearest demonstrations to date of the reinforcing effects of caffeine in capsules and in coffee.     

When Manipulation Gets Personal

Many accounts of moral responsibility have emerged recently that question the importance of conscious choice for moral responsibility. Instead of this ‘volitional’ requirement, these ‘attributionist’ accounts claim that agents are responsible for their actions when their actions reflect who they are and what they value. This paper argues that attributionist accounts are too quick to dismiss the connection between volition and moral responsibility. By excising conscious control from their accounts, attributionists leave open the undesirable possibility that an agent may fulfil all necessary conditions for moral responsibility even when she is under the conscious control of another person. Through analyzing situations in which attributionist conditions for moral responsibility are met while an agent is controlled by someone else, the link between an agent's volition and her moral responsibility becomes more apparent.     

German students’ current choice of profession in the field of psychotherapy

The psychoanalytic societies in Germany as in many other countries are concerned by a decline in the number of candidates for full psychoanalytic training. While this situation is partly attributable to changes both in society and in educational and healthcare systems, it is questionable whether psychoanalytic training institutions have yet found adequate responses to it. Under the banner of ‘evidence‐based treatment’, behaviour therapy has come to be widely disseminated, with major implications for the teaching of different psychotherapy paradigms at universities. To investigate the determinants of this trend in the specific German situation, a large‐scale, multi‐method exploratory study supported by IPA's DPPT programme was undertaken, focusing on the reasons given by a population (N = 679) of German psychology, medical, and education students for embarking on training in psychoanalysis or behaviour therapy. The results suggest that behaviour therapy is more compatible with the prevailing scientific understanding and with current societal and cultural trends, owing in part to inadequacies or bias in university teaching of the various paradigms of psychotherapy. While most of the psychology students expressed a preference for behavioural training, the psychotherapy option proved less attractive for their counterparts in the fields of medicine and education. Semi‐standardized qualitative interviews were used to gain a deeper understanding of the students’ decisions for or against training in a specific paradigm, and led to the identification of seven decision‐making prototypes. Possible reasons for the students’ decisions are discussed, and concrete proposals and recommendations are presented.     

Choice of Weapon or Weapon of Choice? Examining the Interactions between Victim Characteristics in Single‐victim Male Sexual Homicide Offenders

As most studies report that the majority of sexual homicide offenders (SHOs) prefer to kill with their own hands, research has largely neglected to examine the choice of weapon by these offenders. The US Supplementary Homicide Reports show that although a large number of SHOs murder their victim using personal weapons (e.g. bare hands and manual or ligature strangulation), the majority use an alternative weapon (e.g. edged weapons, contact weapons, and firearms). The present study hypothesises that the choice of weapon is in part influenced by victim characteristics. To identify specific combinations and interactions between victim characteristics and the choice of a personal or edged weapon during the commission of a sexual homicide, a combination of exhaustive chi‐square automatic interaction detector and conjunctive analysis is used on a sample of 2,472 single‐victim male SHOs from a 36‐year period of Supplementary Homicide Report data (1976–2011). Findings show that SHOs choose their weapon according to some victim characteristics. Implications of the findings are discussed in light of police suspect prioritisation. Copyright © 2014 John Wiley & Sons, Ltd.