The regression trunk approach to discover treatment covariate interaction

The regression trunk approach (RTA) is an integration of regression trees and multiple linear regression analysis. In this paper RTA is used to discover treatment covariate interactions, in the regression of one continuous variable on a treatment variable withmultiple covariates. The performance of RTA is compared to the classical method of forward stepwise regression. The results of two simulation studies, in which the true interactions are modeled as threshold interactions, show that RTA detects the interactions in a higher number of cases (82.3% in the first simulation study, and 52.3% in the second) than stepwise regression (56.5% and 20.5%). In a real data example the final RTA model has a higher cross-validated variance-accounted-for (29.8%) than the stepwise regression model (12.5%). All of these results indicate that RTA is a promising alternative method for demonstrating differential effectiveness of treatments. Supported by The Netherlands Organization for Scientific Research (NWO), grant 030-56403 to Jacqueline Meulman for the Pioneer project “Subject-Oriented Multivariate Analysis,” and grant 451-02-058 to Elise Dusseldorp for the Veni project “Modeling interaction effects as small trees in regression and classification.” We thank Bram Bakker for making the data of his doctoral dissertation available, and David Hand, Jerome Friedman, Bart Jan van Os, Philip Spinhoven, and the anonymous reviewers for their helpful suggestions. Special thanks are due to Lawrence Hubert.     

Dissociating mere exposure and repetition priming as a function of word type

The mere exposure effect is defined as enhanced attitude toward a stimulus that has been repeatedly exposed. Repetition priming is defined as facilitated processing of a previously exposed stimulus. We conducted a direct comparison between the two phenomena to test the assumption that the mere exposure effect represents an example of repetition priming. In two experiments, having studied a set of words or nonwords, participants were given a repetition priming task (perceptual identification) or one of two mere exposure (affective liking or preference judgment) tasks. Repetition priming was obtained for both words and nonwords, but only nonwords produced a mere exposure effect. This demonstrates a key boundary for observing the mere exposure effect, one not readily accommodated by a perceptual representation systems (Tulving & Schacter, 1990) account, which assumes that both phenomena should show some sensitivity to nonwords and words.     

Learning in a simple motor system

Motor learning is a very basic, essential form of learning that appears to share common mechanisms across different motor systems. We evaluate and compare a few conceptual models for learning in a relatively simple neural system, the vestibulo-ocular reflex (VOR) of vertebrates. We also compare the different animal models that have been used to study the VOR. In the VOR, a sensory signal from the semicircular canals is transformed into a motor signal that moves the eyes. The VOR can modify the transformation under the guidance of vision. The changes are persistent and share some characteristics with other types of associative learning. The cerebellar cortex is directly linked to the VOR reflex circuitry in a partnership that is present in all vertebrates, and which is necessary for motor learning. Early theories of Marr, Albus, and Ito, in which motor memories are stored solely in the cerebellar cortex, have not explained the bulk of the experimental data. Many studies appear to indicate a site of learning in the vestibular nuclei, and the most successful models have incorporated long-term memory storage in both the cerebellar cortex and the brainstem. Plausible cellular mechanisms for learning have been identified in both structures. We propose that short-term motor memory is initially stored in the cerebellar cortex, and that during consolidation of the motor memory the locus of storage shifts to include a brainstem site. We present experimental results that support our hypothesis.     

The relationship of relatives' attributions to their expressed emotion and to patients' improvement in treatment for anxiety disorders

In a test of Hooley's (1987) attributional model of expressed emotion (EE), attributions for negative behaviors and events in patients' lives were examined in relatives of 74 outpatients with panic disorder with agoraphobia or obsessive-compulsive disorder. Attributions were extracted from 10-minute problem-solving interactions between relatives and patients, whereas EE was assessed during a separate interview with the relative. Consistent with prior findings in relatives of individuals with other disorders, relatives who made greater proportions of attributions of patient responsibility demonstrated significantly higher levels of EE-hostility. In addition, nonspousal relatives (mostly parents) who attributed any negative behaviors or events to a patient's disorder were significantly higher in emotional overinvolvement (EOI); no such relationship was found for spouses. Finally, patients with relatives who made attributions to the patient's disorder received less benefit from behavior therapy than did those whose relatives made no such attributions, even when EE variables were controlled.     

Reliability and validity of the Revised Children's Manifest Anxiety Scale in a French-Canadian sample

The aim of this study was to examine the reliability and validity of a French version of the Revised Children's Manifest Anxiety Scale (RCMAS). A sample of 2,666 school-age French-Canadian children completed the questionnaire. With regard to factor structure, the 5-factor model found in U.S. normative samples was confirmed. The internal consistency of the 5 scales and of the 2 global scales was good to excellent. Test-retest reliabilities after a 6-month period were also similar to those of the original version. Finally, the concurrent validity, assessed by a correlation with the State-Trait Anxiety Inventory for Children, was also found to be good. Results of the present study show that the French version of the RCMAS is a good instrument to assess anxiety in children.     

Motion sickness preceded by unstable displacements of the center of pressure

We exposed standing participants to optic flow in a moving room. Motion sickness was induced by motion that simulated the amplitude and frequency of standing sway. We identified instabilities in displacements of the center of pressure among participants who became sick; these instabilities occurred before the onset of subjective motion sickness symptoms. Postural differences between Sick and Well participants were observed before exposure to the nauseogenic stimulus. During exposure to the nauseogenic stimulus, sway increased for participants who became sick but also for those who did not. However, at every point during exposure sway was greater for participants who became motion sick. The results reveal that motion sickness is preceded by instabilities in displacements of the center of pressure.     

Reach Out and Reduce Prejudice: The Impact of Interpersonal Touch on Intergroup Liking

A brief, casual interpersonal touch results in positive behavior toward the toucher, presumably because touch is a cue to friendship. Research on intergroup contact shows that feelings of friendship toward an individual outgroup member reduce prejudice toward that entire group. Integrating these areas, we examined whether interpersonal touch by an outgroup member could reduce prejudice. In three replications in two studies, interpersonal touch decreased implicit, though not explicit, prejudice toward the toucher's group. Effects of interpersonal touch can extend beyond the toucher to others sharing the toucher's ethnicity, and findings suggest that such effects are automatic and outside conscious awareness.     

Reduction in Memory Specificity Following an Approach/Avoidance Scrambled Sentences Task Relates to Cognitive Avoidant Coping

Overgeneral autobiographical memory (OGM) refers to the tendency to retrieve less specific personal memories. According to the functional avoidance hypothesis, OGM might act as a cognitive strategy to avoid emotionally distressing details of negative memories. In the present study, we investigated the effect of an experimentally induced avoidant state on memory specificity. We primed an avoidant state in half of the participants and an approaching state in the other half by means of a Scrambled Sentences Task (SST). Memory specificity was measured before and after priming. Trait cognitive avoidant coping was assessed prior to the experiment. Analyses indicated that higher trait avoidance was significantly associated with lower memory specificity after the SST and stronger reductions in memory specificity from pre- to post-SST, irrespective of the priming condition. The latter suggests that the SST triggered high avoiders’ avoidance schema in both conditions, possibly because it was experienced as a stressor.