The symmetrical law of effect and the matching relation in choice behavior

In a concurrent-chains procedure, pigeons chose between outcomes that differed in the rate of response-independent delivery of food and electric shocks. The application of functional measurement techniques confirmed the matching relation—between choice and rate of reinforcement value—for two of three pigeons. Scale values of the outcomes were extracted for the two birds that conformed to matching, and the value of a single occurrence of shock per minute—in terms of negative food units—was estimated. A second experiment with concurrent chains provided a test of these parameter estimates. The close correspondence between predicted and obtained choice behavior found in Experiment II indicated that the estimates of outcome value were indeed reliable. Both experiments together support the contention that the effects on choice behavior of positive and aversive stimuli appear to be equal, though opposite in sign.     

The role of discriminative stimuli in concurrent performances

Key pecking in pigeons was examined under concurrent and parallel arrangements of two independent and simultaneously available variable-interval schedules. Pecks on the changeover key alternated the schedule of reinforcement for responses on the main key. Under concurrent schedules, discriminative stimuli were paired with the reinforcement schedule arranged in each component and changeover responses also alternated these stimuli. Under parallel schedules, changeover responses alternated the effective reinforcement schedule, but did not change the discriminative stimulus. On concurrent procedures, changeover response rate was inversely related to the difference in reinforcement rate between the two components, whereas on parallel schedules no consistent relationship was found. With both schedules, absolute response and reinforcement rates were positively related, although for a given set of reinforcement frequencies, rates were often higher on the concurrent schedules. On concurrent schedules, relative response rates and relative times were equal to relative reinforcement rates. On parallel schedules these ratios were positively related, but response and time ratios were much smaller than were obtained with comparable concurrent schedules. This inequality was most pronounced when absolute reinforcement frequencies were lowest.     

Response and time allocation in concurrent second-order schedules

Six pigeons were trained on two-key concurrent variable-interval schedules in which the required response was the completion of a fixed number of key pecks. When the required number of pecks was equal on the two keys, response- and time-allocation ratios under-matched obtained reinforcement rate ratios. A similar result was found when the required number of pecks was unequal, except that performance, measured in response terms, was biased to the shorter required number of pecks and was less sensitive to reinforcement-rate changes. No such differences were found in the data on time spent responding. When the variable-interval schedules were kept constant and the required numbers of pecks were systematically varied, response ratios changed inversely with the ratio of the required number of pecks, but time-allocation ratios varied directly with the same independent variable. Thus, on response measures, pigeons “prefer” the schedule with the smaller peck requirement, but on time measures they “prefer” the schedule with the larger peck requirement. This finding is inconsistent with a commonsense notion of choice, which sees response and time-allocation measures as equivalent.     

Quantitative studies of reinforcement relativity

Three experiments examined an application of the matching law to the area of reinforcement relativity. In Experiment I, rats ran in a wheel and drank a sucrose solution. Equations derived from the matching law made fairly accurate predictions of the amounts of time spent running and drinking when licks and wheel revolutions had to occur in fixed proportions. In Experiment II, rats were required to spend four times as much time drinking as running, but the absolute durations of the cycles of drinking and running were varied. Except for the shortest cycle size tested, durations were close to those predicted. Experiments III investigated a tendency for obtained durations of running and drinking to be slightly longer than predicted. Simply shortening the periods when these behaviors were available increased their values. It was concluded that the matching law equations provided reasonably accurate predictions in some experiments, but changes in motivation set the limits of such accuracy.     

The effect of punishment on free-operant choice behavior in humans

During Phase I, three female human subjects pressed a button for monetary reinforcement in five variable-interval schedules specifying different frequencies of reinforcement. On alternate days, responding was also punished (by subtracting money) according to a variable-ratio 34 schedule. In the absence of punishment, response rates conformed to Herrnstein's equation for single variable-interval schedules. Punishment suppressed responding at all frequencies of reinforcement. This was reflected in a change in the values of both constants in Herrnstein's equation: the value of the theoretical maximum response-rate parameter was reduced, and the parameter describing the reinforcement frequency corresponding to the half-maximal response rate was elevated. During Phase II, the same five schedules (A) were in operation (without punishment), but in addition, a concurrent variable-interval schedule (B) of standard reinforcement frequency was introduced. On alternate days, responding in Component B was punished according to a variable-ratio 34 schedule. In the absence of punishment, absolute response rates conformed to equations proposed by Herrnstein to describe performance in concurrent schedules; the ratios of the response rates in the two components and the ratios of the times spent in the two components conformed to the Matching Law. When responding in Component B was punished, response rates in Component B were reduced and those in Component A were elevated, these changes being reflected in distortions of the matching relationship.     

Biology and a Theology of Evolution

The challenge and stimulus to theology that is constituted by the scientific version of Genesis which will prevail for the foreseeable future is expounded in relation to the significance of the succeeding stages of the life process and to the general features of biological evolution. A responsive theology of evolution is discerned as involving a renewal of insights associated with the themes of immanence, panentheism, the Wisdom and Word of God, and a sacramental universe. Such a revitalized theology allows one to conceive of humanity and Jesus the Christ in a fully evolutionary perspective without loss of an emphasis on the particularity of the Incarnation.     

The Matching Law And Amount-dependent Exponential Discounting As Accounts Of Self-control Choice

Studies with humans have found evidence for amount-dependent temporal discounting, that is, that the sensitivity of choice to reinforcer delay varies inversely with reinforcer magnitude. To test whether similar results could be obtained with nonhumans, pigeons were trained on a two-component concurrent-chains procedure in which the durations of food reinforcement in the terminal links were equal within components but unequal between components. Terminal-link schedules were varied over four conditions to allow separate estimates of sensitivity to delay to be obtained for the large and small reinforcer-magnitude components. Although sensitivity to delay was greater in the small-magnitude component for all subjects, the effect was quite small. The difference in sensitivity was generally less than one standard error, and t tests on parameter differences failed to reach significance. Several models for temporal discounting, including an amount-dependent exponential function, were fitted to the data from the first four conditions. The resulting parameter estimates were used to make predictions for a self-control condition in which one terminal link arranged a smaller, less delayed reinforcer and the other arranged a larger, more delayed reinforcer. For all models, predictions were considerably more accurate when sensitivity to delay was the same regardless of reinforcer magnitude. The results support the independence of delay and magnitude as required by a version of the matching law, and provide strong evidence against amount-dependent exponential discounting as an account of self-control choice. A new two-parameter discounting function, consistent with the matching law, is proposed that has wide empirical generality for both human and nonhuman data.     

Kant: The Audacity of Judgement

In the legal judgement reason demands that it extend itself beyond the mere subjective limits of the self in order that it might fashion a judgement that speaks for the other. This is the universal necessity of the judgement. No claim of truth or the moral law can guarantee that others will agree with this judgement: thus disputation is the risk which reason takes in order to judge at all. The author examines this audacity of judgement by reference to Kant's autonomy of reason, which risks itself in the thought that thinks. This revised version was published online in June 2006 with corrections to the Cover Date.     

The Professional Autonomy of the Medical Doctor in Italy

This contribution deals with the issue of the professional autonomy ofthe medical doctor. Worldwide, the physician's autonomy is guaranteedand limited, first of all, by Codes of Medical Ethics. InItaly, the latest version of the national Code of MedicalEthics (Code 1998) was published in 1998 by the Federation ofprovincial Medical Associations (FnomCeO). The Code 1998acknowledges the physician's autonomy regarding the scheduling, thechoice and application of diagnostic and therapeutic means, within theprinciples of professional responsibility. This responsibility has tomake reference to the following fundamental ethical principles:(1) the protection of human life; (2) the protection of thephysical and psychological health of the human being; (3) therelief from pain; (4) the respect for the freedom and the dignityof the human person, without discrimination; (5) an up-to-datescientific qualification (Art. 5). The authors underline that autonomyis an anthropological – and consequently ethical –characteristic of the human person. Different positions on autonomy inbioethics (individualistic, evolutionistic, utilitarian andpersonalistic models) are explained. The relation between theprofessional autonomy of the physician and the autonomy of the patientand of colleagues is discussed. In fact, the medical doctor isobliged: (1) to respect the fundamental rights of the person,first of all his/her life; (2) to ensure the continuity of thecare, even if he can only relieve the patient's suffering; (3) tomaintain, except under certain circumstances, professional secrecy andconfidentiality regarding patients and their medical records. Moreover,the physician cannot deny the patient correct and appropriateinformation. He/she should not perform any diagnostic or therapeuticactivity without the informed consent of the patient and the medicaldoctor must give up medical treatment in case of documented refusal ofthe individual. Furthermore, the medical doctor has the right to raiseconscientious objections if he/she is requested to perform medicalactions that are contrary to his/her conscience or medical opinion,unless this attitude would seriously and immediately harm the patient.Regarding the relationships with colleagues, the physician is obliged tosolidarity, mutual respect, and care of sick colleagues. Finally, theauthors discuss the Italian legislation affecting the physician'sprofessional autonomy: (1) the SSN health care Acts; (2) theso-called Charter for Public Health Care Services; (3) the Acts onprivacy; (4) Good Clinical Practice.