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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 paper examines the changes over time in the spatial dispersion of facilities in a bounded one-dimensional habitat. Each facility produces a single good for a unique market area and demand for the good varies inversely with distance to the nearest facility and increases uniformly over time. Production and transportation cost functions are not assumed to be linear, and it is assumed that market areas are chosen so as to minimise the average cost of producing and transporting unit amount of the good. Conditions relating the demand function to the transportation cost function are given which are necessary and/or sufficient for the size of the market area to decrease over time. It is shown that if the market area has constant size, ‘balanced growth’ occurs if and only if the demand function is of the Pareto type. Finally, the relevance to this analysis of economies of scale is discussed.

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.

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.