Inflated discrete Beta regression models for Likert and discrete rating scale outcomes

Discrete ordinal responses such as Likert scales are regularly proposed in questionnaires and used as dependent variable in modeling. The response distribution for such scales is always discrete, with bounded support and often skewed. In addition, one particular level of the scale is frequently inflated as it cumulates respondents who invari- ably choose that particular level (typically the middle or one extreme of the scale) without hesitation with those who chose that alternative but might have selected a neighboring one. The inflated discrete beta regression (IDBR) model addresses those four critical characteristics that have never been taken into account simultaneously by existing models. The mean and the dispersion of rates are jointly regressed on covariates using an underlying beta distribution. The probability that choosers of the inflated level invariably make that choice is also regressed on covariates. Simulation studies used to evaluate the statistical properties of the IDBR model suggest that it produces more precise predictions than competing models. The ability to jointly model the location and dispersion of (the distribution of) an ordinal response, as well as to characterize the profile of subject selecting an ”inflated” alternative are the most relevant features of the IDBR model. It is illustrated with the analysis of the political positioning on a ”left-right” scale of the Belgian respondents in the 2012 European Social Survey

Default-name and tasting nudges increase salsify soup choice without increasing overall soup choice

Nudging is a popular behavior change technique but the conditions for its effectiveness have not been researched extensively. The current study aimed to test whether the effectiveness of nudging is limited to certain characteristics of the nudged product by focusing on a specific product (salsify soup) within a broader category (soups). Two parallel studies were conducted in two sandwich restaurants in a university setting at which a default-name nudge (“suggestion of the chef”) and a tasting nudge were implemented aimed at increasing the choice for salsify soup using a non-randomized study design during 10 and 12 measurement days. The beta-regression model showed that the default-name nudge increased the proportion of customers that choose the salsify soup during intervention days compared to non-intervention days, p < .001, OR: 1.70. The tasting nudge also increased the proportion of customers that choose the salsify soup from baseline to intervention, p < .001, OR: 6.17 and from baseline to post-intervention, p < .01, OR: 1.87, and decreased from intervention to post-intervention, p < .001, OR: 0.30. Both nudges did not increase the choice for the overall category of soups. The results show that certain types of nudges are able to increase specific products of a category without increasing overall choice of a category in contrast to previous findings

Investigating the conditions for the effectiveness of nudging: Cue-to-action nudging increases familiar vegetable choice

Inulin-type fructans (ITF), which are fibres found in vegetables such as salsify, artichoke and Jerusalem artichoke, are known for their prebiotic capacities and may contribute to preventing obesity. The current study aimed to assess the differential effects of a type-2 and a combined type-1 and -2 nudge to increase the choice for “prebiotic” vegetables at a hot vegetable buffet of a university restaurant, using a nonrandomized intervention study design involving two interventions during five consecutive weeks. An intervention was implemented in which customers were exposed to type-2 nudging in the form of short “cue-to-action” messages placed on their trays and above the hot vegetable buffet, and an additional type-1 nudging intervention was implemented in the form of placing dishes with “prebiotic” vegetables in a more accessible place. On average, 28 servings of hot vegetables were registered on a total of 503 meals sold at the restaurant per day. The beta regression model showed that the “cue-to-action” intervention increased the proportion of customers who used the hot vegetable buffet (p <.001, OR: 1.24), but that the proportion of “prebiotic” vegetables chosen decreased during the “cue-to-action” intervention weeks (p <.01, OR: 0.73). The cue-to-action intervention increased familiar vegetable choice in general and decreased unfamiliar prebiotic vegetable choice. The additional intervention of increasing the accessibility did not change prebiotic vegetable choice. The effectiveness of nudging seems to depend on the specificity and/or the familiarity of the nudged products

Daily Life Stressors and Coping Strategies During Widowhood: A Diary Study After One Year of Bereavement

The present study examined the frequency and types of bereavement-related stressors and coping strategies that 40 widowed people encountered and reported in a diary over the course of 1 week. The results indicated that, after 1 year of bereavement, (1) the most frequent stressors were oriented to the loss of the spouse, (2) specific coping strategies were used and found effective to deal with specific types of stressors, (3) stressors were sometimes dealt with using several successive strategies or no strategy at all, and (4) clusters of stressors and strategies were associated with specific moments of appearance during the day

The composition of cuticular compounds indicates body parts, sex and age in the model butterfly Bicyclus anynana (Lepidoptera)

Chemical communication in insects’ sexual interactions is well-known to involve olfaction of volatile compounds called sex pheromones. In theory, sexual chemical communication may also involve chemicals with low or no volatility exchanged during precopulatory gustatory contacts. Yet, knowledge on this latter type of chemicals is so far mostly restricted to the Drosophila fly model. Here we provide the most comprehensive characterization to date of the cuticular chemical profile, including both volatile and non-volatile compounds, of a model butterfly, Bicyclus anynana. First, we characterized the body distribution of 103 cuticular lipids, mostly alkanes and methyl-branched alkanes, by gas chromatography coupled to mass spectrometry (GC-MS). Second, we developed a multivariate statistical approach to cope with such complex chemical profiles and showed that variation in the presence or abundance of a subset of the cuticular lipids indicated body parts, and traits involved in B. anynana mate choice, namely sex and age. Third, we identified the chemical structure of the 20 most indicative compounds, which were on average more abundant (1346.4 ± 1994.6 ng; mean ± SD) than other, likely less indicative, compounds (225.9 ± 507.2 ng; mean ± SD). Fourth, we showed that wings and legs displayed most of the chemical information found on the entire body of the butterflies. Fifth, we showed that non-random gustatory contacts occurred between specific male and female body parts during courtship. The body parts mostly touched by the conspecific displayed the largest between-sex differentiation in cuticular composition. Altogether, the large diversity of cuticular lipids in B. anynana, which exceeds the one of Drosophila flies, and its non-random distribution and evaluation across individuals, together suggest that gustatory information is likely exchanged during sexual interactions in Lepidoptera