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Participants recruited from one Historically Black University (HBU) and two predominantly White higher-education institutions evaluated and decided simulated voting rights case summaries in which the plaintiff was either a racially-defined (African American) or a nonracially-defined (farmers) minority group. Contrary to social identity and social justice findings of an in-group bias, the present study showed greater support at all institutions for the voting rights of the African Americans than for the rural farmers, and the greatest support for both minority groups was found at the HBU. Perceived evidence strength was a better predictor of decisions than perceived unfairness, and both of these predictor variables completely mediated the effects of institution-type and involvement of a racially-defined group on decisions.

Link and Heath [1975] have analysed a random walk model for two-choice reaction time on the assumption that the two probability density functions (p.d.f.s) of the step-size, each p.d.f. corresponding to one stimulus, are mirror reflections of each other; and they have demonstrated the critical role played by the symmetry of the moment generating function (m.g.f.) of the step size in the determination of whether or not error and correct reaction times are equal. It is shown here that, given reflection symmetry, m.g.f. symmetry is necessary and sufficient for the random walk model to be equivalent to a sequential probability ratio test.

This article analyzes the game-theoretic stability of three strategies, Tit-For-Tat (TFT), all-Defect (all-D), and all-Cooperate (all-C), that actors might use for repeated plays of the Prisoner's Dilemma (PD). The probability that there will be a next play is assumed to depend on the current behavior of one of the actors—it is w after cooperation and u after a defection—and two cases are examined. The first case is where an actor assumes that the continuation probability depends on its own behavior, and the second is where the continuation probability is assumed to depend on the other actor's behavior. It is shown that the potential for mutual cooperation is higher in the first case than in the second. A detailed examination of the first case reveals that when the ratio (1 - w)/(1 - u) is sufficiently extreme for certain classes of PD, the “cooperative” strategy TFT is stable and the “noncooperative” strategy all-D is unstable. For these classes of PD, it is thus possible both for cooperation to be maintained once it is established, and for cooperation to become established in a world of defectors. The sensitivity of these results to the precision in measurement of payoffs and probabilities is discussed.

This article considers the problem of finding the optimal rule for assigning liability on the basis of fault when there is (a) error in the assessment of fault, (b) a probability distribution of true fault across the population of possible litigants, and (c) a value attached to the deterrence effect of a rule. The discussion is placed in the legal context of Contributory Negligence, and parallels are drawn between the present approach and the ‘economic’ approach to liability. A contributory negligence rule is said to be optimal if it minimizes a weighted sum of the cost of assessment error and the cost of the deviation between a rule and the ‘optimally deterrent’ rule. It is shown that the form of the optimal rule depends on the ‘importance’ of deterrence and on the probability distribution of plaintiffs with respect to fault. Sufficient conditions are given for each of the extant contributory negligence rules to approximate the optimal rule. It is argued that, in designing the law, the preference among rules should be based on the relative plausibility of these sufficient conditions, some of which may be verifiable empirically.

Hypotheses are stated about the relationships among the level of task difficulty chosen by a subject in a sequential task, expectancy of success, own outcome and that of a paired subject, and satisfaction with own outcome. Multiple regression analyses were used to test these hypotheses on data from an experiment in which subjects worked in pairs for six trials. It was found that the difficulty level chosen on a given trial was predicted by the difficulty level, the subject's outcome score, and the subject's satisfaction on the previous trial; that level of satisfaction on a trial was predicted by the subject's own outcome score and the difference in outcome scores between the two subjects on that trial; and that expectancy was predicted by difficulty level on the same trial. These results underscore the important mediating role of outcome evaluation in the control of behavior, and are consistent with previous research showing a dependence of evaluation on social comparison processes. Also consistent with previous research is the observed trend over trials to more difficult tasks. The “slope” of this trend depended on the initial difficulty level, a result which is readily accounted for by a simplified version of our hypotheses.

This paper examines the equilibrium relation between the wage and profit rates for a technology in which technical parameters vary continuously. It is shown that the existence of a wage-profit frontier implies the existence of functional relationships among the technical parameters. These relationships, called herein characteristic functions, can be expressed in terms of one or more than one independent variable, and it is shown that given certain weak conditions on the functions, only in the former case is reswitching of techniques possible. An inequality is established involving the rates of change, as the profit rate varies, of the technical parameters; it is argued that this inequality can be used to construct functions that order the eligible techniques. Finally, it is argued that the characteristic functions can embody specific, nontechnical relations, so that a “technology” should be broadly interpreted as a collection of techniques of production plus “exogenous” relations that determine which techniques are to be included in the technology.

Five groups of fictitious case outlines were prepared about a plaintiff who sued a defendant for damages. Within each group of cases, we independently manipulated evidence about the apparent fault (here labeled the propensity to fault) in the plaintiffs conduct and in the defendant's conduct, as well as evidence about the severity of the harm. Subjects rated the responsibility of the plaintiff and the defendant for the harm and assessed the liability against the defendant. The data were consistent with a hierarchical model of identification and attributional processes in which propensity influences responsibility, which in turn, influences liability. Analyses based on a measure of relative responsibility suggested that the rule, liability should be proportional to fault, was an inadequate description of the data. This finding is discussed in the context of the legal doctrines of contributory and comparative negligence.

An experiment in typing is described in which the visual spacing in the text and the amount of linguistic structure in the material are varied. The results show that average typing speed is decreased both by removing visual spaces from the text and by decreasing the amount of structure in the material. The data are interpreted as evidence that there is response grouping in a typist's output, and a model is stated in which this grouping is attributed to the operation of a response-unit scanner. More detailed analysis by means of this model suggests a picture of serial and parallel information processing to be an adequate representation of the conversion of text into type.

SUMMARY Given a sample from each of three populations, it is sometimes of interest to decide whether the distribution function of one of the populations is a linear mixture of the distribution functions of the other two populations. This paper discusses distribution free procedures for testing such a hypothesis.

The notion of expectancy has often been used in explanations of the relationship between foreperiod variability and simple reaction time. Two interpretations of the notion are distinguished: one is that expectancy or expectancy level is a moment in time, and the other is that expectancy is a regular function of time. The latter interpretation is adopted and it is shown that if expectancy is defined as the conditional probability of signal occurrence, then average reaction time would be linearly related to mean foreperiod duration. It is argued that this result can serve as a basis for unifying apparently diverse explanations of the reaction time—foreperiod relationship. Experimental data are presented which are consistent with the view of expectancy proposed in this paper.

When the Limiting Method is used to measure heat-pain threshold, the observed threshod has been shown to depend on the size of the stimulus increment used (Haslam, 1965). An experiment is reported here which repeats a finding of the experiment referred to above that the variability of threshold is relatively large when the stimulus increment is small. A statistical analysis of the data shows that the previously untested hypothesis that pain threshold is uniform over the population (Hardy, Wolff and Goodell, 1952) is a reasonable one. The psychological implications of threshold variability are discussed in the light of a theoretical model, and a criterion for an optimum interval in the assessment of heat-pain threshold is discussed.

A model developed by Cane (1956) for the study of relative thresholds is modified to apply to absolute thresholds. It is assumed that the fluctuation in the subject's sensation of a stimulus is uniformly distributed, and the model is used to estimate the threshold from data presented by several authors.