Through the eyes of dieters: Biased size perception of food following tempting food primes

Why do some dieters succeed in controlling their diet while others do not? This research focused on a perceptual process—size perception of food objects—that may moderate the success of dieters in self-control dilemmas. We assessed successful and unsuccessful dieters' size perception of palatable food (Study 1) and diet-food (Study 2) after pre-exposing them to tempting food primes. Dieters perceived palatable food as bigger when primed with tempting food (vs. control prime), regardless of self-regulatory success in dieting (Study 1). Palatable food thus looms larger for both unsuccessful and successful dieters when in a “hot” state. In contrast, the perceived size of diet-food was increased by a tempting food prime only for successful dieters, but decreased for unsuccessful dieters (Study 2). These results are interpreted in terms of differences in the mental accessibility of competing goals (eating enjoyment vs. dieting) in successful vs. unsuccessful dieters. Indeed, when the dieting goal was made accessible for all dieters by a diet prime, even unsuccessful dieters perceived diet-food as bigger (Study 2). This research provides insight into a perceptual process that may be detrimental or beneficial in resolving self-control conflicts in the domain of eating and dieting behavior—and probably other domains of self-control as well.     

音乐节奏和共餐人数对就餐时间的影响

本实验采用现场实验研究的方法,对不同音乐节奏和共餐人数条件下大学生就餐时间的差异进行了分析。结果表明:(1)总的来说,音乐节奏对就餐时间的主效应是显著的,快节奏音乐下的就餐时间少于慢节奏下的就餐时间;(2)单人组被试就餐时间显著快于多人组被试共餐时间;(3)音乐节奏和共餐人数对就餐时间存在交互作用;(4)在单人就餐时音乐节奏对就餐时间的效应是显著的,而多人共餐则没有这种效应或效应不显著。     

Evaluating a model of global psychophysical judgments—I: Behavioral properties of summations and productions

The research presented is a partial empirical evaluation of the second author's proposed psychophysical theory [Luce (2002). Psychological Review, 109, 520-532; Luce (2004). Psychological Review, 111, 446-454]. The theory deals with the global percept of subjective intensity, in which there is a psychophysical function Ψ that maps pairs of physical intensities onto the positive real numbers and represents, in an explicit mathematical way, subjective summation and a form of ratio production. A number of behavioral properties have been shown to follow from these specific representations, and in the presence of certain plausible background assumptions these properties are also sufficient for the representations. In four auditory experiments, key behavioral properties of summation over the two ears and a form of generalized ratio production are evaluated empirically. Considerable support is reported for particular forms of Ψ for summations and ratio productions separately. A second article, Steingrimsson and Luce (Journal of Mathematical Psychology, in press), explores the behavioral properties that link summations and productions.     

Class size effects on literacy skills and literacy interest in first grade: A large-scale investigation

This article examines the impact of class size on literacy skills and on literacy interest in beginning readers from zones with specific educational needs in France. The data came from an experiment involving first graders in which teachers and pupils were randomly assigned to the different class types (small classes of 10-12 pupils vs. regular classes of 20-25 pupils).Globally, the findings reveal that class size has a (small) impact on the two basic literacy skills, reading (word recognition task) and spelling (word production task). Children with high literacy interest made more progress than children with low literacy interest. The analysis also explores the effect of four factors - early schooling, age, first language and socio-economic status - on the same type of literacy skills as above. Smaller classes most specifically improved performances in two types of population: children whose first language is French and children from intermediate and average socio-economic brackets. This means, in contrast, that neither the children from the most disadvantaged backgrounds nor the children whose first language was not French benefited from the use of smaller first grade classes. Data in this experiment are examined in the light of studies on the connections between class size, classroom procedures and pupils' engagement.     

Stevens’ Direct Scaling Methods and the Uniqueness Problem

Stevens postulated that we can use the responses of a participant in a ratio scaling experiment directly to construct a psychophysical function representing the participant's sensations. Although Stevens' methods of constructing measurement scales are widely used in the behavioral sciences, the problem of which scale type is appropriate to describe ratio scaling data is still unresolved. To deal with this problem, we develop a theoretical framework to specify the scale type attained by Stevens' direct scaling methods. It is shown, under fairly mild background assumptions, that the behavioral axioms presented in this paper are necessary and sufficient for the psychophysical functions to be ordinal-, interval-, log-interval-, or ratio-scales. Furthermore, suggestions on how to test these behavioral axioms are provided. Requests for reprints should be sent to thomas.     

Nonparametric Estimation of Standard Errors in Covariance Analysis Using the Infinitesimal Jackknife

The infinitesimal jackknife provides a simple general method for estimating standard errors in covariance structure analysis. Beyond its simplicity and generality what makes the infinitesimal jackknife method attractive is that essentially no assumptions are required to produce consistent standard error estimates, not even the requirement that the population sampled has the covariance structure assumed. Commonly used covariance structure analysis software uses parametric methods for estimating parameters and standard errors. When the population sampled has the covariance structure assumed, but fails to have the distributional form assumed, the parameter estimates usually remain consistent, but the standard error estimates do not. This has motivated the introduction of a variety of nonparametric standard error estimates that are consistent when the population sampled fails to have the distributional form assumed. The only distributional assumption these require is that the covariance structure be correctly specified. As noted, even this assumption is not required for the infinitesimal jackknife. The relation between the infinitesimal jackknife and other nonparametric standard error estimators is discussed. An advantage of the infinitesimal jackknife over the jackknife and the bootstrap is that it requires only one analysis to produce standard error estimates rather than one for every jackknife or bootstrap sample.     

Regularized Partial and/or Constrained Redundancy Analysis

Methods of incorporating a ridge type of regularization into partial redundancy analysis (PRA), constrained redundancy analysis (CRA), and partial and constrained redundancy analysis (PCRA) were discussed. The usefulness of ridge estimation in reducing mean square error (MSE) has been recognized in multiple regression analysis for some time, especially when predictor variables are nearly collinear, and the ordinary least squares estimator is poorly determined. The ridge estimation method was extended to PRA, CRA, and PCRA, where the reduced rank ridge estimates of regression coefficients were obtained by minimizing the ridge least squares criterion. It was shown that in all cases they could be obtained in closed form for a fixed value of ridge parameter. An optimal value of the ridge parameter is found by G-fold cross validation. Illustrative examples were given to demonstrate the usefulness of the method in practical data analysis situations. We thank Jim Ramsay for his insightful comments on an earlier draft of this paper. The work reported in this paper is supported by Grants 10630 from the Natural Sciences and Engineering Research Council of Canada to the first author.     

Combining standardized mean differences using the method of maximum likelihood

A maximum likelihood procedure for combining standardized mean differences based on a noncentratt-distribution is proposed. With a proper data augmentation technique, an EM-algorithm is developed. Information and likelihood ratio statistics are discussed in detail for reliable inference. Simulation results favor the proposed procedure over both the existing normal theory maximum likelihood procedure and the commonly used generalized least squares procedure.     

Preschoolers’ nonsymbolic arithmetic with large sets: Is addition more accurate than subtraction?

Adult and developing humans share with other animals analog magnitude representations of number that support nonsymbolic arithmetic with large sets. This experiment tested the hypothesis that such representations may be more accurate for addition than for subtraction in children as young as 3½ years of age. In these tasks, the experimenter hid two equal sets of cookies, visibly added to or subtracted from the sets, and then asked 3½-year-olds which set had more cookies. Initial set size was either large (7 or 9) or very large (18 or 30), and the final sets differed by either a high proportion (ratio of 1:2) or a low proportion (difference of 1 cookie). Children’s addition performance exceeded chance, as well as their subtraction performance, across set sizes and proportions, whereas subtraction performance did not exceed chance. Arithmetic performance was also independent of counting ability. Addition performance was remarkably accurate when ratios between outcomes were close to 1, in contrast to previous findings. Interpretations for the asymmetry between addition and subtraction are discussed with respect to the nature of representations for nonsymbolic arithmetic with large sets.     

Gender Differences in Body Size Dissatisfaction Among Individuals With Low,Medium, or High Levels of Body Focus

The authors designed the present study to test whether women reported higher levels of body dissatisfaction than did men even when the 2 genders were matched on a measure of degree of body focus. Sixty undergraduates (30 men, 30 women) were screened on attention-to-body-shape scores and divided into high, medium, and low body-shape-focus groups. The participants also completed questionnaires that provided information on age, education, vocabulary ability, levels of depression, and body-image assessment. The groups did not differ (ps > .05) on age, education, vocabulary ability, or levels of depression. However, women in all 3 body-shape-focus categories indicated a larger discrepancy between their real vs. ideal body images (p < .01) than did the men. In the high-body-focus group, there was an 11:1 ratio between women's and men's reported real-ideal body-shape discrepancies. Women showed greater body dissatisfaction than did men, even when the genders were matched on a measure of body focus.