Adjusting researchers’ approach to adjustment: On the use of covariates when testing interactions

A common design in social psychology involves the use of two independent variables, an experimental manipulation and a measured individual difference, and the interest is in the interaction between them. In such designs, there are often obvious covariate(s), correlated with the measured independent variable, which the researcher wishes to control. Typically this is done by including the covariate in the analytic model. We show that in most cases this is an inadequate model. In general, the interaction between the two independent variables will be estimated without bias only when the interaction between the covariate and the manipulated independent variable is included in the analysis. We present simulations showing the factors affecting the magnitude of the bias and provide a survey of recent social psychological literature illustrating the frequency of the problem. Finally, we discuss cases where both independent variables are manipulated and the covariate is a potential mediator.     

Coaction and upward social comparison reduce the illusory conjunction effect: Support for distraction-conflict theory

This article proposes an integration of Festinger’s (1954) social comparison theory and Baron’s (1986) distraction-conflict theory of the social facilitation-inhibition effect, which successfully predicts attentional focusing in coaction when social comparison represents a distraction. Two experiments confronted participants with the illusory conjunction task (Treisman, 1998), where illusions occur because of the lack of attentional processing of central cues. If coaction, like upward comparison, is distracting and thereby enhances the attention allocated to central cues (here the target’s features) at the expense of peripheral cues (here distractors), then a reduction should be found in the illusions. Experiment 1 indeed showed a lower rate of conjunctive errors under upward comparison than under downward comparison. Experiment 2 specified that this effect was due to downward comparison effectively reducing distraction, with upward comparison only maintaining it, as compared to mere coaction.     

Delay discounting: Interactions between personality and cognitive ability

Delay discounting describes the extent to which the value of a reward decreases as the delay to obtaining that reward increases. Lower discounting rates predict better outcomes in social, academic, and health domains. The current study investigates how personality and cognitive ability interact to predict individual differences in delay discounting. Extraversion was found to predict higher discounting rates at the low end of the cognitive distribution, while emotional stability was found to predict lower discounting rates at the high end of the cognitive distribution. These findings support recent models of discounting behavior and suggest that personality and cognitive ability interact in shaping decision making.     

Increasing convergence between imagined and executed movement across development: evidence for the emergence of movement representations

Motor imagery (MI) has become a principal focus of interest in studies on brain and behavior. However, changes in MI across development have received virtually no attention so far. In the present study, children (N = 112, 6 to 16 years old) performed a new, computerized Virtual Radial Fitts Task (VRFT) to determine their MI ability as well as the age‐related confluence between performance in executed and imagined movement conditions. Participants aimed at five targets, which were positioned along radial axes from a central target circle. The targets differed in width (2.5, 5, 10, 20 or 40 mm), resulting in an index of difficulty (ID) that varied from 6.9 to 2.9 bits. Performance was indexed by the linear relationship between ID and Movement Time (MT). The findings showed that executed task performance was slower than imagined performance. Moreover, conformance to Fitts’ Law during executed movement performance was obtained from a very young age. Most importantly, correlations between imagined and executed movements were low in the young participants but gradually increased across age. These age‐related changes in MI are hypothesized to reflect the children's emerging ability to represent internal models for prospective actions, consistent with the gradual unfolding of feedforward control processes.     

Modeling continuity and discontinuity in utterance length: a quantitative approach to changes, transitions and intra-individual variability in early grammatical development

The confluence of an anomaly such as a growth spurt or a temporary regression on the one hand and a temporary increase in intra-individual variability on the other hand, forms a strong indicator of a major transition in early language development. Data concern one-word (W1), two- and three-word (W2-3), and four-and-more-word (W4+) utterances from two French children during their second and third years. A dynamic growth model was fitted, based on a structure of supportive, conditional and competitive relationships. Using a statistical simulation method, we showed two striking peaks of variability in addition to a temporary regression or rapid growth in the proportions of W1, W2-3 and W4+ utterances. We argue that these phenomena show transitions corresponding to critical points in grammatical development, which could be indicative of the emergence of simple combinatorial and syntactic stages of language successively. Our results emphasize the relevance of time-serial data and of intra-individual variability in the study of developmental transitions in general.     

Toward the use of approach/avoidance tendencies as attitude measures: Individual- and group-level variability of the ingroup bias

Approach/avoidance paradigms could constitute an interesting alternative in measuring intergroup attitudes, notably if they overcome one criticism often addressed toward classic indirect tasks: Measuring attitudes beyond the influence of cultural knowledge. Using intergroup stimuli and a population likely to be exposed to a similar cultural knowledge, we observed two informative results regarding this issue: Approach/avoidance effects measured by the Visual Approach/Avoidance by the Self Task (VAAST) varied across participants (i.e., consistent with the variability of intergroup attitudes; Experiment 1) and both participants of dominant and non-dominant groups produced an ingroup bias (Experiment 2). A last experiment (Experiment 3) showed that compatibility scores in the VAAST predict trustworthiness ratings of the ingroup/outgroup. This experiment also investigated potential differences between the VAAST and the IAT. These results suggest that approach/avoidance tasks (notably the VAAST) could be relevant to assess personal attitudes when it comes to normatively sensitive topics.