Neurobiological studies of risk assessment: A comparison of expected utility and mean-variance approaches

When modeling valuation under uncertainty, economists generally prefer expected utility because it has an axiomatic foundation, meaning that the resulting choices will satisfy a number of rationality requirements. In expected utility theory, values are computed by multiplying probabilities of each possible state of nature by the payoff in that state and summing the results. The drawback of this approach is that all state probabilities need to be dealt with separately, which becomes extremely cumbersome when it comes to learning. Finance academics and professionals, however, prefer to value risky prospects in terms of a trade-off between expected reward and risk, where the latter is usually measured in terms of reward variance. This mean-variance approach is fast and simple and greatly facilitates learning, but it impedes assigning values to new gambles on the basis of those of known ones. To date, it is unclear whether the human brain computes values in accordance with expected utility theory or with mean-variance analysis. In this article, we discuss the theoretical and empirical arguments that favor one or the other theory. We also propose a new experimental paradigm that could determine whether the human brain follows the expected utility or the mean-variance approach. Behavioral results of implementation of the paradigm are discussed

Neurobiological studies of risk assessment: A comparison of expected utility and mean-variance approaches

When modeling valuation under uncertainty, economists generally prefer expected utility because it has an axiomatic foundation, meaning that the resulting choices will satisfy a number of rationality requirements. In expected utility theory, values are computed by multiplying probabilities of each possible state of nature by the payoff in that state and summing the results. The drawback of this approach is that all state probabilities need to be dealt with separately, which becomes extremely cumbersome when it comes to learning. Finance academics and professionals, however, prefer to value risky prospects in terms of a trade-off between expected reward and risk, where the latter is usually measured in terms of reward variance. This mean-variance approach is fast and simple and greatly facilitates learning, but it impedes assigning values to new gambles on the basis of those of known ones. To date, it is unclear whether the human brain computes values in accordance with expected utility theory or with mean-variance analysis. In this article, we discuss the theoretical and empirical arguments that favor one or the other theory. We also propose a new experimental paradigm that could determine whether the human brain follows the expected utility or the mean-variance approach. Behavioral results of implementation of the paradigm are discusse

Adolescent Impulsivity: Findings From a Community Sample

Impulsivity is central to several psychopathological states in adolescence. However, there is little consensus concerning the definition of impulsivity and its core dimensions. In response to this lack of consensus, Whiteside and Lynam (2001, Pers. Individ. Differ. 30, 669-689) have developed the UPPS Impulsive Behavior Scale, which is able to distinguish 4 dimensions of impulsivity in adults: Urgency, lack of Premeditation, lack of Perseverance, and Sensation seeking. The question arises of whether these 4 dimensions also exist in adolescents and also of whether gender differences can be observed. A sample of teenagers (314 girls and 314 boys) completed a French version of the scale (Van der Linden et al., Eur. J. Psychol. Assess., 2005). Based on exploratory and confirmatory analyses, the 4-factor model is replicated in girls, boys, and the whole sample. Concerning gender differences, girls have a higher score for Urgency and boys a higher score for Sensation seeking. Overall, this study suggests that the UPPS is a promising tool for studying impulsivity in adolescenc

Memory for Angry Faces, Impulsivity, and Problematic Behavior in Adolescence

Research has shown that cognitive processes like the attribution of hostile intention or angry emotion to others contribute to the development and maintenance of conduct problems. However, the role of memory has been understudied in comparison with attribution biases. The aim of this study was thus to test if a memory bias for angry faces was related to conduct problems in youth. Adolescents from a junior secondary school were presented with angry and happy faces and were later asked to recognize the same faces with a neutral expression. They also completed an impulsivity questionnaire. A teacher assessed their behavior. The results showed that a better recognition of angry faces than happy faces predicted conduct problems and hyperactivity/inattention as reported by the teacher. The memory bias effect was more pronounced for impulsive adolescents. It is suggested that a memory bias for angry faces favors disruptive behavior but that a good ability to control impulses may moderate the negative impact of this bia

Rapid Diagnostic Tests for Non-Malarial Febrile Illness in the Tropics

The recent roll-out of rapid diagnostic tests (RDTs) for malaria has highlighted the decreasing proportion of malaria-attributable illness in endemic areas. Unfortunately, once malaria is excluded, there are few accessible diagnostic tools to guide the management of severe febrile illnesses in low resource settings. This review summarizes the current state of RDT development for several key infections, including dengue fever, enteric fever, leptospirosis, brucellosis, visceral leishmaniasis and human African trypanosomiasis, and highlights many remaining gaps. Most RDTs for non-malarial tropical infections currently rely on the detection of host antibodies against a single infectious agent. The sensitivity and specificity of host-antibody detection tests are both inherently limited. Moreover, prolonged antibody responses to many infections preclude the use of most serological RDTs for monitoring response to treatment and/or for diagnosing relapse. Considering these limitations, there is a pressing need for sensitive pathogen-detection-based RDTs, as have been successfully developed for malaria and dengue. Ultimately, integration of RDTs into a validated syndromic approach to tropical fevers is urgently needed. Related research priorities are to define the evolving epidemiology of fever in the tropics, and to determine how combinations of RDTs could be best used to improve the management of severe and treatable infections requiring specific therapy

Low quality of routine microscopy for malaria at different levels of the health system in Dar es Salaam

ABSTRACT: BACKGROUND: Laboratory capacity to confirm malaria cases in Tanzania is low and presumptive treatment of malaria is being practiced widely. In malaria endemic areas WHO now recommends systematic laboratory testing when suspecting malaria. Currently, the use of Rapid Diagnostic Tests (RDTs) is recommended for the diagnosis of malaria in lower level peripheral facilities, but not in health centres and hospitals. In this study, the following parameters were evaluated: (1) the quality of routine microscopy, and (2) the effects of RDT implementation on the positivity rate of malaria test results at three levels of the health system in Dar es Salaam, Tanzania. METHODS: During a baseline cross-sectional survey, routine blood slides were randomly picked from 12 urban public health facilities in Dar es Salaam, Tanzania. Sensitivity and specificity of routine slides were assessed against expert microscopy. In March 2007, following training of health workers, RDTs were introduced in nine public health facilities (three hospitals, three health centres and three dispensaries) in a near-to-programmatic way, while three control health facilities continued using microscopy. The monthly malaria positivity rates (PR) recorded in health statistics registers were collected before (routine microscopy) and after (routine RDTs) the intervention in all facilities. RESULTS: At baseline, 53% of blood slides were reported as positive by the routine laboratories, whereas only 2% were positive by expert microscopy. Sensitivity of routine microscopy was 71.4% and specificity was 47.3%. Positive and negative predictive values were 2.8% and 98.7%, respectively. Median parasitaemia was only three parasites per 200 white blood cells (WBC) by routine microscopy compared to 1226 parasites per 200 WBC by expert microscopy. Before RDT implementation, the mean test positivity rates using routine microscopy were 43% in hospitals, 62% in health centres and 58% in dispensaries. After RDT implementation, mean positivity rates using routine RDTs were 6%, 7% and 8%, respectively. The sensitivity and specificity of RDTs using expert microscopy as reference were 97.0% and 96.8%. The positivity rate of routine microscopy remained the same in the three control facilities: 71% before versus 72% after. Two cross-sectional health facility surveys confirmed that the parasite rate in febrile patients was low in Dar es Salaam during both the rainy season (13.6%) and the dry season (3.3%). CONCLUSIONS: The quality of routine microscopy was poor in all health facilities, regardless of their level. Over-diagnosis was massive, with many false positive results reported as very low parasitaemia (1 to 5 parasites per 200 WBC). RDTs should replace microscopy as first-line diagnostic tool for malaria in all settings, especially in hospitals where the potential for saving lives is greates