Smoothing spline ANOVA decomposition of arbitrary splines: an application to eye movements in reading

On the ambiguity of interaction and nonlinear main effects in a regime of dependent covariates

The analysis of large experimental datasets frequently reveals significant interactions that are difficult to interpret within the theoretical framework guiding the research. Some of these interactions actually arise from the presence of unspecified nonlinear main effects and statistically dependent covariates in the statistical model. Importantly, such nonlinear main effects may be compatible (or, at least, not incompatible) with the current theoretical framework. In the present literature, this issue has only been studied in terms of correlated (linearly dependent) covariates. Here we generalize to nonlinear main effects (i.e., main effects of arbitrary shape) and dependent covariates. We propose a novel nonparametric method to test for ambiguous interactions where present parametric methods fail. We illustrate the method with a set of simulations and with reanalyses (a) of effects of parental education on their children's educational expectations and (b) of effects of word properties on fixation locations during reading of natural sentences, specifically of effects of length and morphological complexity of the word to be fixated next. The resolution of such ambiguities facilitates theoretical progress.

Sliding into happiness: A new tool for measuring affective responses to words

Reliable measurement of affective responses is critical for research into human emotion. Affective evaluation of words is most commonly gauged on multiple dimensions-including valence (positivity) and arousal-using a rating scale. Despite its popularity, this scale is open to criticism: It generates ordinal data that is often misinterpreted as interval, it does not provide the fine resolution that is essential by recent theoretical accounts of emotion, and its extremes may not be properly calibrated. In 5 experiments, the authors introduce a new slider tool for affective evaluation of words on a continuous, well-calibrated and high-resolution scale. In Experiment 1, participants were shown a word and asked to move a manikin representing themselves closer to or farther away from the word. The manikin's distance from the word strongly correlated with the word's valence. In Experiment 2, individual differences in shyness and sociability elicited reliable differences in distance from the words. Experiment 3 validated the results of Experiments 1 and 2 using a demographically more diverse population of responders. Finally, Experiment 4 (along with Experiment 2) suggested that task demand is not a potential cause for scale recalibration. In Experiment 5, men and women placed a manikin closer or farther from words that showed sex differences in valence, highlighting the sensitivity of this measure to group differences. These findings shed a new light on interactions among affect, language, and individual differences, and demonstrate the utility of a new tool for measuring word affect. (PsycINFO Database Record