Reexamining the circumplex model of affect.

The circumplex model of affect has been among the most widely studied representations of affect. Despite the considerable evidence cited in support of it, methods typically used to evaluate the model have substantial limitations. In this article, the authors attempt to correct past limitations by using a covariance structure model specifically designed to assess circumplex structure. This model was fit to 47 individual correlation matrices from published data sets. Analyses revealed that model fit was typically acceptable and that opposing affective states usually demonstrated strong negative correlations with one another. However, analyses also indicated substantial variability in both model fit and correlations among opposing affective states and suggested several characteristics of studies that partially accounted for this variability. Detailed examination of the locations of affective states for 10 of the correlation matrices with relatively optimal characteristics provided mixed support for the model.

Thinking about Russia: plausible pasts and probable futures.

This paper uses both correlational and experimental methods to explore the power of counterfactual cognitions about the past to constrain judgments about the future as well as policy preferences. Study 1 asked 47 specialists on the Soviet Union to assess both the plausibility of controversial counterfactuals and the probability of controversial conditional forecasts. The results reveal deep ideological schisms, with liberals much more likely than conservatives to believe that Stalinism was not inevitable, that the Cold War could have ended earlier, and that Gorbachev might have succeeded in democratizing the Soviet Union if he had been a better tactician, among others. Reactions to these counterfactuals proved to be highly predictive of positions that experts in early 1992 endorsed concerning the advisability of 'shock therapy', expanding NATO eastward, and economic aid to Russia. Study 2 manipulated the salience and plausibility of counterfactual scenarios concerning (a) why the Cold War ended as it did, and (b) how close the US and USSR came to nuclear war. Changes in the counterfactual scenarios that non-experts endorsed produced significant changes in their policy preferences in the direction suggested by the salient counterfactual. Experts, however, were unswayed, often generating counter-arguments against dissonant counterfactuals. Taken together, the studies show that assumptions about what happened in the missing control conditions of history are highly subjective, largely theory-driven and profoundly consequential.

Development of attitude strength over the life cycle: surge and decline.

This article explores the relation of age to manifestations and antecedents of attitude strength. Three studies demonstrate that susceptibility to attitude change is greater during early and late adulthood than during middle adulthood. Three additional studies demonstrate that attitude importance, certainty, and perceived quantity of attitude-relevant knowledge are greater in middle adulthood than during early or late adulthood. These antecedents may therefore explain life cycle shifts in susceptibility to change. Susceptibility to change, importance, certainty, and perceived knowledge differ from one another in terms of their correlations with education, gender, and race, challenging the notion that attitude strength is a unitary construct. Evidence that people incorrectly believe that susceptibility to change declines steadily over the life course reinforces the distinction between operative and meta-attitudinal measures of attitude strength.

Conceptual and methodological issues in testing the circumplex structure of data in personality and social psychology.

Circumplex representations of data have enjoyed widespread popularity in personality and social psychological research. In this article we review the conceptual assumptions implied by circumplex representations and we discuss the limitations of traditional statistical methods for testing these assumptions. A relatively nontechnical overview of a new covariance structure modeling approach to testing circumplex structure is provided. The use of this approach is illustrated with two published data sets. The advantages and disadvantages of this approach relative to more traditional statistical approaches are discussed. The conclusion is that the covariance structure modeling approach has significant advantages in that it provides a closer conceptual match to the theoretical assumptions of circumplex representations, supplies information more directly relevant to circumplex representations and permits more precise and flexible testing of hypotheses derived from circumplex representations.

Entamoeba histolytica: naturally occurring infections in baboons.

Entamoeba chattoni frequently occurs as an intestinal infection in non-human primates. It has been isolated from both wild and captive animals. Morphologically this amoeba resembles E. histolytica. E. histolytica has also been isolated from non-human primates on a number of occasions but these isolations have been from captive animals. In recent years identification of E. histolytica has been enhanced by the introduction of iso-enzyme electrophoresis methods. This technology has been widely applied to amoebae isolated from humans from many parts of the world. Limited work using iso-enzyme electrophoresis on non-human primates in captivity has confirmed the earlier parasitological studies mentioned above as both E. histolytica and E. chattoni were isolated; furthermore zymodeme (strain or species based on the characteristic iso-enzyme electrophoretic pattern) analysis demonstrated that these two organisms could be readily distinguished by this method. The importance of establishing whether E. histolytica occurs in wild primates as a true zoonosis was emphasised by these studies, particularly from the point of view of potential disease transmission. A study of baboons (Papio ursinus) in South African game reserves has been initiated and three surveys have been conducted in the Kruger National Park; these baboons are considered to live in isolation from humans. Of the 210 isolations attempted 65-75% yielded E. chattoni while E. histolytica were cultured from the faeces of 1-3% of the baboons. Although the prevalence rates varied in each of the 3 study locations both species of amoeba were found in baboons from all of them. All the E. histolytica isolated thus far have been non-pathogenic zymodemes.(ABSTRACT TRUNCATED AT 250 WORDS)

The tegument of Schistosoma hippopotami from Hippopotamus amphibius in the Kruger National Park.

Schistosoma hippopotami were collected from the right heart chambers and pulmonary arteries of Hippopotamus amphibius culled in the Kruger National Park. The schistosomes were subjected to scanning electron microscopy as well as optical microscopy. The results indicate that S. hippopotami is not conspecific to S. mansoni as suggested in the literature. On account of the morphology of certain tegumental structures of both male and female parasites, it is suggested that S. hippopotami is adapted to the pulmonary arterial circulation of its host.

Notes on the occurrence of tubercular spines in Schistosoma margrebowiei and Schistosoma mattheei.

Scanning electron microscopical (SEM) studies on the tegument of the bovid schistosomes, Schistosoma margrebowiei and Schistosoma mattheei have yielded conflicting results; certain authors observed the tubercles on the tegument of these species to be spined, while others reported that they are spineless. The present study indicates that the protrusion of tubercular spines is subject to phenotypic plasticity regulated by external factors such as the identity of the host species and whether or not the schistosome is paired.

Phenotypic differences in Schistosoma mattheei ova from populations sympatric and allopatric to S. haematobium.

Schistosoma mattheei ova were collected from cattle in different localities in South Africa and after hatching, miracidia were used to infest Bulinus (Physopsis) globosus. Cercariae harvested from these snails were used to infest the definitive host Praomys (Mastomys) coucha and eggs from the resulting female S. mattheei were collected. These ova were compared with a Schistosoma haematobium X S. mattheei hybrid similarly collected from an infested P. (M.) coucha. The results indicate that S. mattheei populations which are sympatric to S. haematobium possess S. haematobium characteristics. It is suggested that the gene pools of populations of the parasite in these areas are infiltrated with S. haematobium genes via the S. mattheei X S. haematobium hybrid originating from human hosts.

False-positive reactions in the serological diagnosis of schistosomiasis.

Stool and urine samples from children living in an area in the Western Transvaal in which human schistosomiasis was not endemic were examined for parasites and the indirect fluorescent antibody test was performed on their sera. Since none of these children passed any schistosome ova in their excreta but approximately half of them had a positive serological reaction they must have been infected with either Schistosoma mattheei, which is common in snails and cattle in the area, or avian schistosomes. In view of the occurrence of such 'false-positive' results, general practitioners are advised not to rely too heavily on serological tests in the diagnosis of schistosomiasis.

Schistosoma mattheei Veglia & LE Roux, 1929, egg output from cattle in a highly endemic area in the eastern Transvaal.

The results of 6-month estimations of S. mattheei faecal egg counts on 513 cattle in a highly endemic area of the eastern Transvaal over a 2-year period are given. After an initial high egg output of short duration the egg counts stabilized at a low level. The frequency of high egg counts in young cattle which died naturally was more than twice that of all other cattle, suggesting that S. mattheei egg counts in highly endemic areas is debatable, and it is suggested that egg counts in man might follow a similar pattern.

Schistosoma Weinland, 1858 from Hippopotamus amphibius Linnaeus, 1758 in the Kruger National Park.

Adults of Schistosoma edwardiense Thurston, 1964, were recovered from Hippopotamus amphibius in the Kruger National Park. Small round to oval Schistosoma margrebowiei-like eggs, presumed to be those of S. edwardiense, were found fairly frequently in the faeces of infected hippopotami together with a few Schistosoma haematobium-like eggs the identity of which remains uncertain. Biomphalaria sp., exposed to the droppings of infected hippopotami, shed cercariae thought to be those of S. edwardiense. No evidence of schistosoma adults was found at necropsy in rodents exposed to these cercariae. The parasite appears to be host specific to the hippopotamus. Arguments, based on biological and anatomical characteristics are put forward regarding Schistosoma hippopotami Thurston, 1963 as synonymous with Schistosoma mansoni.

Excretion of Schistosoma mattheei eggs from man, baboons and cattle living in their normal environment.

Egg excretion of S. mattheei was studied for about a year from man, baboons and cattle living in their normal environment. Although the excretory pattern was not unequivocal from man, there was a tendency of egg counts to decline with time: the baboons showed a seasonal pattern and the cattle a stable pattern throughout the year.