Risk perception is a phenomenon in search of an explanation. Several approaches are discussed in this paper. Technical risk estimates are sometimes a potent factor in accounting for perceived risk, but in many important applications it is not. Heuristics and biases, mainly availability, account for only a minor portion of risk perception, and media contents have not been clearly implicated in risk perception. The psychometric model is probably the leading contender in the field, but its explanatory value is only around 20% of the variance of raw data. Adding a factor of "unnatural risk" considerably improves the psychometric model. Cultural Theory, on the other hand, has not been able to explain more than 5-10% of the variance of perceived risk, and other value scales have similarly failed. A model is proposed in which attitude, risk sensitivity, and specific fear are used as explanatory variables; this model seems to explain well over 30-40% of the variance and is thus more promising than previous approaches. The model offers a different type of psychological explanation of risk perception, and it has many implications, e.g., a different approach to the relationship between attitude and perceived risk, as compared with the usual cognitive analysis of attitude.

Risk perception is sometimes measured by means of judgments about worry, sometimes as perceived risk more directly. However, perceived level of risk calls for a more intellectual judgment and worry tends to refer to emotional reactions. These two are therefore not the same and need not be strongly correlated. Results reported here show that perceived risk and worry are indeed weakly correlated, both for generalized worry and for more specific measures of worry matched with the same hazard as risk ratings. A distinction is suggested between cognitive, abstract hazards and concrete, sensory hazards, with implications for the worry-perceived risk relationship. It was furthermore found by means of cluster analysis that there were groups of subject displaying different dynamics of risk and worry.

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The present study investigated the extent to which inter-personal skills, personality, and emotional intelligence (EI) were related to the extent of usage of the Internet, as measured with the Internet Addiction Scale, on a sample of undergraduates. EI was assessed by performance measures derived from the identification and labeling of emotions as shown in pictures of facial expressions, and as interpreted from descriptions of social episodes. Use of the Internet was related to loneliness and adherence to idiosyncratic values (strong effects), and also to poorer balance between work and leisure and emotional intelligence (weaker effects). Big Five personality dimensions were also included in the study. No link was found between personality and usage of the Internet. Results suggest that frequent users tend to be lonely, to have deviant values, and to some extent to lack the emotional and social skills characteristic of high EI.

All episodes of Clostridium difficile associated diarrhea (CDAD) diagnosed in a defined population of 274,000 including one tertiary and two primary hospitals and their catchment areas were studied during 12 months. The annual CDAD incidence in the county was 97 primary episodes per 100,000, and 78% of all episodes were classified as hospital associated with a mean incidence of 5.3 (range, 1.4 to 6.5) primary episodes per 1,000 admissions. The incidence among hospitalized individuals was 1,300-fold higher than that in the community (33,700 versus 25 primary episodes per 100,000 persons per year), reflecting a 37-fold difference in antibiotic consumption (477 versus 13 defined daily doses [DDD]/1,000 persons/day) and other risk factors. Three tertiary hospital wards with the highest incidence (13 to 36 per 1,000) had CDAD patients of high age (median age of 80 years versus 70 years for other wards, P < 0.001), long hospital stay (up to 25 days versus 4 days), or a high antibiotic consumption rate (up to 2,427 versus 421 DDD/1,000 bed days). PCR ribotyping of C. difficile isolates available from 330 of 372 CDAD episodes indicated nosocomial acquisition of the strain in 17 to 27% of hospital-associated cases, depending on the time interval between index and secondary cases allowed (2 months or up to 12 months), and only 10% of recurrences were due to a new strain of C. difficile (apparent reinfection). In other words, most primary and recurring episodes were apparently caused by the patient's endogenous strain rather than by one of hospital origin. Typing also indicated that a majority of C. difficile strains belonged to international serotypes, and the distribution of types was similar within and outside hospitals and in primary and relapsing CDAD. However, type SE17 was an exception, comprising 22% of hospital isolates compared to 6% of community isolates (P ‫؍‬ 0.008) and causing many minor clusters and a silent nosocomial outbreak including 36 to 44% of the CDAD episodes in the three high-incidence wards.

Perceived risk and related attitudes have been implicated as major factors in many of the difficult policy problems that face modern society (nuclear power, genetically modified food, etc). Experts often argue that no or very small risks are involved; people are still worried. Why? The standard answer is lack of trust. Data on trust and risk perception, however, point to only a weak relationship between the two ( r approximately 0.3). It is suggested here that the reason for the surprisingly minor importance of trust is that people believe that there are clear limits to how much science and experts know. Results are presented from studies of risk perception of the public, experts, and politicians. Politicians and members of the public believe that there are many unknown effects of technology and such beliefs were strongly related to their perceived risk. Experts on nuclear waste, on the other hand, seemed to believe that little is unknown in their field of expertise. Regression analyses of risk perception showed the unknown-effects factor to be a more important explanatory factor than trust for the public and politicians.KEY WORDS: Trust; risk perception; demand for risk mitigation; experts; politicians the understanding of risk perception and policy attitudes.(3-6) Many papers on trust and risk perception treat the matter mostly as a theoretical problem and present no data. It seems to be simply assumed that the relationship is very strong.Empirical data, however, do not support this commonsense notion. Examples of empirical investigations of the matter converge on the conclusion that the relationship is not strong, but rather weak to moderate. (Higher correlations might have resulted, in some cases, from the use of more reliable measures of trust and perceived risk.) Pijawka and Mushkatel (7) studied risk perception of nuclear waste and trust in the federal government, federal agencies, and state and local government. They specified trust as a belief that decisions taken will protect public safety (probably in general). The correlations with risk perception expressed a 5-10% explained variance in perceived risk on the basis of trust. The same level was reported by Bord and O'Connor (8) in a study of a hazardous waste site. Trust measures were of those in general. Hallman and Wandersman (9) investigated a hazard-

Due to unfortunate choices of response scale and psychometric model earlier analyses of mood adjective check lists have given a confused and complex picture of the area. When an adequate response scale was applied and a simplex rather than a common factor analysis model was utilized it was found, in two empirical studies, that mood was possible to describe with a few bipolar factors. A theory is suggested where mood is seen as basically two‐dimensional: one dimension being activity and the other pleasantness. More or less specific definitions of the content of experience with reference to the situation may then be used to define further dimensions, such as social orientation.

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