The probability of war in then-crises problem: Modeling new alternatives to Wright's solution

In hisStudy of War, Q. Wright considered a model for the probability of warP during a period ofn crises, and proposed the equationP=1–(1–p) ⁿ , wherep is the probability of war escalating at each individual crisis. This probability measure was formally derived recently by Cioffi-Revilla (1987), using the general theory of political reliability and an interpretation of the n-crises problem as a branching process. Two new, alternate solutions are presented here, one using D. Bernoulli's St. Petersburg Paradox as an analogue, the other based on the logic of conditional probabilities. Analysis shows that, while Wright's solution is robust with regard to the general overall behavior ofp andn, some significant qualitative and quantitative differences emerge from the alternative solutions. In particular,P converges to 1 only in a special case (Wright's) and not generally.C.C.-R. acknowledges support provided by the Merriam Laboratory for Analytic Political Research, the Research Board of the University of Illinois, and grant SES-84-00877 from the U.S. National Science Foundation.     

Interactions between area and numerosity

Summary The concept of filled area, i.e. the impressionistic ensemble of parts of a stimulus field occupied by dots, is used to account for various kinds of numerosity illusions due to perceptual interaction between a number of dots and their spatial arrangement. A measure of filled area is derived from a model for the perceptual clustering of dots on the basis of relative proximity. It is shown that the quantified concept of filled area successfully predicts illusion data from earlier studies. Subsequently, a two-alternatives forced-choice numerosity experiment is reported, the data of which gave further evidence of the predictive power of the filled-area hypothesis. Our approach is discussed with respect to spatial features of dot stimuli that might be in rivalry with the filled-area factor in numerosity-estimation tasks.     

Does spreading activation summate?

Summary Network models of semantic memory assume implicitly or explicitly that the degree of activation of a node is a monotonic function of the total amount of excitation reaching that node from all sources. For example, the activation level of the node representing apple should be greater if it is receiving excitation due to the activation of the nodes for fruit and pear than if only one of these neighboring nodes is activated. This notion was tested by presenting semantic primes 80 ms or 320 ms before a letter string (e.g., apple or ipple) requiring a lexical decision. The prime stimuli consisted of a pair of simultaneous items that were identical in the single prime condition (e.g., fruit/fruit or pear/pear) or different in the double prime condition (e.g., fruit/pear or pear/fruit), and were either related (target = apple) or unrelated (target = copper) to the target, or neutral. As predicted by the summation of semantic activation assumption of network models there was a larger priming effect (in the 320 ms SOA condition) following the simultaneous activation of two related nodes than following the activation of only one node.This research was supported by grants to the first author from the Natural Sciences and Engineering Research Council of Canada.     

Many stimuli are frightening,but some are more frightening than others: The contributions of preparedness,dangerousness, and unpredictability to making a stimulus fearful

The nonrandom distribution of situational fears has been explained by evolutionary survival relevance of specific fears. Thirty-eight stimuli were taken from the literature on preparedness and were scored on fearfulness, objective dangerousness, and spatiotemporal unpredictability by three separate groups of students. The same items were scored on survival relevance by 15 biologists. Fearfulness of cues significantly correlated not only with survival relevance but also, and even more strongly, with dangerousness and unpredictability. While the fear/survival relevance association virtually disappeared when the unpredictability contribution was partialed out, the fear/unpredictability correlation was only marginally affected when controlling for survival relevance. This suggests that nonrandomness of feared stimuli may result from the spatiotemporal unpredictability that is attributed to these stimuli. The current practice of using snakes and spiders as phobia-relevant, and flowers and mushrooms as neutral, cues was not justified by the ratings of the 15 independent experts.This study was supported in part by a grant from the Dutch Organization for Fundamental Research (ZWO/Psychon, 560-268-001).     

Risk and behavior: The mediating role of risk appraisal

The main issue of this paper concerns the mediating role of risk appraisal in the relation between past and future behavior. We expected previous risky behavior to heighten risk appraisal, which, in turn, should stimulate preventive behavior. Results ofthree tests of this mediation hypothesis showed that past behavior was strongly related to future behavior; people who behaved hazardously in the past indicated that they tend to do so in the future. Generally, the expected relation between past behavior and risk appraisal was supported. More risky behavior in the past was associated with a heightened risk appraisal. Results also indicate a relation between risk appraisal and future behavior, but in the opposite direction as predicted. Heightened risk appraisal was related to increased levels of risk in future behavior. When predicting future behavior by both risk appraisal and past behavior the effect of risk appraisal on future behavior disappeared, while past behavior remained a strong predictor of future behavior. In a few cases risk appraisal still predicted future behavior when past behavior was controlled for. Unfortunately, these cases showed the opposite relation; i.e., heightened risk appraisal was related to more risky future behavior. Implications of these findings for research on the role of risk appraisal will be discussed.     

No counterregulation after breaking the external restraint of children.

At the present, it is unknown how restraint and binge eating/counterregulation are exactly related. Earlier studies on this relationship suffer from two main shortcomings: the studies are all correlational in nature or could not rule out the contribution of confounding variables such as weight loss. The present study investigated whether a break of restraint is a sufficient condition for the occurrence of counterregulation by studying a restrained sample which is not liable to dieting practices and weight loss. The externally imposed restraint on children with regard to eating sweets was broken. However, after breaking their external restraint the children did not counterregulate. It is discussed whether restraint of food intake is really as important for binge eating as it is claimed to be or whether it is merely a consequence or an epiphenomenon of binge eating.     

Surface perception in pictures.

Subjects adjusted a local gauge figure such as to perceptually "fit" the apparent surfaces of objects depicted in photographs. We obtained a few hundred data points per session, covering the picture according to a uniform lattice. Settings were repeated 3 times for each of 3 subjects. Almost all of the variability resided in the slant; the relative spread in the slant was about 25% (Weber fraction). The tilt was reproduced with a typical spread of about 10 degrees. The rank correlation of the slant settings of different observers was high, thus the slant settings of different subjects were monotonically related. The variability could be predicted from the scatter in repeated settings by the individual observers. Although repeated settings by a single observer agreed within 5%, observers did not agree on the value of the slant, even on the average. Scaling factors of a doubling in the depth dimension were encountered between different subjects. The data conformed quite well to some hypothetical fiducial global surface, the orientation of which was "probed" by the subject's local settings. The variability was completely accounted for by single-observer scatter. These conclusions are based upon an analysis of the internal structure of the local settings. We did not address the problem of veridicality, that is, conformity to some "real object."     

Imputation of missing categorical data by maximizing internal consistency

This paper suggests a method to supplant missing categorical data by reasonable replacements. These replacements will maximize the consistency of the completed data as measured by Guttman's squared correlation ratio. The text outlines a solution of the optimization problem, describes relationships with the relevant psychometric theory, and studies some properties of the method in detail. The main result is that the average correlation should be at least 0.50 before the method becomes practical. At that point, the technique gives reasonable results up to 10–15% missing data.We thank Anneke Bloemhoff of NIPG-TNO for compiling and making the Dutch Life Style Survey data available to use, and Chantal Houée and Thérèse Bardaine, IUT, Vannes, France, exchange students under the COMETT program of the EC, for computational assistance. We also thank Donald Rubin, the Editors and several anonymous reviewers for constructive suggestions.