Tribute to Jean-Yves Jaffray

Tribute to Jean-Yves Jaffray by the French Group of Decision Theory.     

Free energy methods for Bayesian inference: efficient exploration of univariate Gaussian mixture posteriors

Because of their multimodality, mixture posterior distributions are difficult to sample with standard Markov chain Monte Carlo (MCMC) methods. We propose a strategy to enhance the sampling of MCMC in this context, using a biasing procedure which originates from computational Statistical Physics. The principle is first to choose a “reaction coordinate”, that is, a “direction” in which the target distribution is multimodal. In a second step, the marginal log-density of the reaction coordinate with respect to the posterior distribution is estimated; minus this quantity is called “free energy” in the computational Statistical Physics literature. To this end, we use adaptive biasing Markov chain algorithms which adapt their targeted invariant distribution on the fly, in order to overcome sampling barriers along the chosen reaction coordinate. Finally, we perform an importance sampling step in order to remove the bias and recover the true posterior. The efficiency factor of the importance sampling step can easily be estimated a priori once the bias is known, and appears to be rather large for the test cases we considered.     

Significant others and the dynamics of the family network (from the Proches et Parents survey to the Biographies et Entourage survey)

With the increase in separations, family recomposition, and new modes of cohabitation, the contours of the family have become less clearly defined. It has become important to separate the family group from its statistical framework – the household – while taking account, in both time and space, of the interpersonal relationships built up over the life-course. In response to these objectives, the French National Institute of Demographic Studies (INED) conducted two surveys, Proches et Parents in 1990 and Biographies et Entourage in 2001, which use new concepts to address these new family realities: the local family circle which, for an individual, includes family members living in the same municipality, with whom he/she has a close and strong relationship in terms of mutual support and regular contact, and the concept of entourage (contact circle), which includes close relatives, all co-resident persons, whether relatives or not, but also significant others who have marked the individual's life. Far from being limited to the immediate family, the universe of familial and elective relationships covers a much more complex reality whose contours may be limited to the family or extended to a wider circle of relatives and friends. It describes an affective and residential proximity that reveals a mutual support network of varying strength, which may or may not be solicited, which may be avoided or, on the contrary, revived in response to events affecting its members.     

Can ‘art Professions’ Be Bourdieuean Fields Of Cultural Production? The Case Of The Architecture Competition

The difference between ‘artistic and literary fields’ and universes such as architecture usually recognized as ‘art professions’ but which enjoy a far lesser ‘degree of autonomy’ than such fields seemingly constitutes an obstacle to the broader application of the notion of a ‘field of cultural production’ sought by Bourdieu in his Rules of Art. The author of this paper overcomes this obstacle by employing his notion of the ‘field effect’, with the architecture competition serving as the test case. Following Bourdieu, the author replaces the notion of profession with that of the field, for the former is a representation fostered by professional groups themselves. Architecture is a field, but, because architects require clients to construct and realize their works, one unlike the artistic and literary fields, which are markets of symbolic goods where ‘distinterest’ reigns and an autonomy unthinkable elsewhere is enjoyed. However, much like artists and unlike any other ‘professionals’, architects enter competitions, suggesting that this practice is an analytically relevant indicator of the field effect. After defining several of the elements of Bourdieu's relational conceptual matrix (field, illusio, collusion, doxa and space of possibles) and demonstrating that the Baptistery competition in Florence (1401) conforms to Bourdieu's historical beginning point for the process of 'autonomization' of artistic production, I examine a number of competitions from 1401 to 1989 (Berlin Jewish Museum) along with the general properties of competitions (structure and organization, publication and exhibition of results, competitors' economically irrational behaviour, practices of designers and jurors and the associated universe of beliefs), analysing them as those of an artistic field. It is concluded that when architects enter competitions, architecture, at least provisionally resembles an artistic field, for there is a field effect shown by a high degree autonomy, disinterest and the creation of an upside-down world.     

Post-Separation Conflict Trajectories: A Longitudinal Study

Although previous studies have shown that parental separation and parental conflict contribute independently to the adaptation difficulties of young people, there is, as of yet, no precise portrait of how post-separation conflicts evolve. Indeed, some fundamental questions remain unanswered: (1) Do parents who experience few conflicts during their break-up continue to enjoy a harmonious relationship afterward? (2) When parents have a conflictual relationship in the first years after separating, do problems eventually subside? (3) Are a family's characteristics associated with the way a post-separation conflict evolves? The present, exploratory study attempts to provide some answers to these three questions. The sample was composed of 123 boys and girls from 8 to 11 years old. The children and their parents were interviewed on two separate occasions at a 1-year interval. The first interview (time 1) took place 2.5 years after the separation on average. The children were notably asked to give their perception of the parental conflict. Four post-separation conflict trajectories were brought to light. Analysis also targeted three more-specific variables that distinguished these conflict trajectories, namely family income, quality of the relationship with the mother, and the degree of agreement at the time of separation.     

Aesthetic revolt and the remaking of national identity in Québec, 1960–1969

Based on archival and ethnographic data, this article analyzes the iconic-making, iconoclastic unmaking, and iconographic remaking of national identifications. The window into these processes is the career of Saint John the Baptist, patron saint of French Canadians and national icon from the mid-nineteenth century until 1969, when his statue was destroyed by protesters during the annual parade in his honor in Montréal. Relying on literatures on visuality and materiality, I analyze how the saint and his attending symbols were deployed in processions, parades, and protests. From this analysis, I develop the sociological concept of aesthetic revolt, a process whereby social actors rework iconic symbols, redefining national identity in the process. The article offers a theoretical articulation and an empirical demonstration of how the context, content, and the form of specific cultural objects and symbols—national icons—are intertwined in public performance to produce eventful change, and shows why and how the internal material logic and the social life of these icons shape the articulation of new national identities.     

Family Benefits and Fertility: An Econometric Analysis

A population's growth potential is significantly underestimated by conventional calculations of population momentum which assume an immediate drop to replacement level fertility. Here we assume that the growth rate of births linearly declines to zero over a specified time interval, and find simple and intuitively meaningful expressions for the size of the ultimate birth cohort and the resultant population momentum. In particular, we find that the increase in the number of births over the transition is equal to growth at the initial rate for half the time needed to attain a constant birth level. Thus our formula readily calculates the growth potential of a population under a gradual approach to stationarity without the need for a numerical projection. Calculations for actual and hypothetical populations are presented to show the demographic impact of such gradual approaches to zero growth.     

Biomechanical analysis of older adults stepping up: a method of evaluating balance

The aim of this study was to analyze differences in biomechanical parameters between elderly and control participants when stepping up, to evaluate control of balance. Eleven control and 14 elderly participants performed a step from an initial static posture onto a 7-cm-high force plate. For the spontaneous-velocity condition, elderly participants performed a slower progression velocity than control participants. Elderly participants spent proportionally more time in stance phase, with a corresponding decrease in swing phase, than the control participants, irrespective of movement velocity. In contrast, at spontaneous velocity the parameters related to ground-reaction force (GRF) showed that anteroposterior and mediolateral forces at toe-off of the support limb and the slope of vertical force during weight transfer were significantly smaller for the elderly than for control participants. These GRF parameters depended on the stepping-up velocity. The elderly develop a spatiotemporal strategy and reduced movement velocity to control support balance.     

Enhanced rate of resting energy expenditure in women using hormone-replacement therapy: preliminary results

Hormone-replacement therapy (HRT) attenuates the menopause-associated alterations in body composition. It is not known, however, whether this effect is a result of a concomitant increase in energy expenditure. The authors examined whether women submitted to a long-term HRT treatment presented greater energy expenditure than women who had never used HRT. We compared 13 postmenopausal women using HRT (>1 yr) with 13 age- (+/-2 yr) and body-mass-index-matched (BMI; +/-1.5 kg/m2) postmenopausal women not using HRT. Resting energy expenditure (REE; indirect calorimetry), body composition, and daily (DEE) and physical activity (PAEE) energy expenditure (accelerometry) were obtained. Although BMI, fat mass, fat-free mass, DEE, and PAEE were similar between groups, the HRT group displayed a significantly greater REE than the no-HRT group (Delta +222 kcal/day). In conclusion, the authors observed that a long-term treatment with HRT is associated with a greater REE in postmenopausal women. These results need to be confirmed.