Propensity score estimation with boosted regression for evaluating causal effects in observational studies

Causal effect modeling with naturalistic rather than experimental data is challenging. In observational studies participants in different treatment conditions may also differ on pretreatment characteristics that influence outcomes. Propensity score methods can theoretically eliminate these confounds for all observed covariates, but accurate estimation of propensity scores is impeded by large numbers of covariates, uncertain functional forms for their associations with treatment selection, and other problems. This article demonstrates that boosting, a modern statistical technique, can overcome many of these obstacles. The authors illustrate this approach with a study of adolescent probationers in substance abuse treatment programs. Propensity score weights estimated using boosting eliminate most pretreatment group differences and substantially alter the apparent relative effects of adolescent substance abuse treatment.     

Induced biases in emotional interpretation influence stress vulnerability and endure despite changes in context

Previous research has shown that interpretation biases can be experimentally induced and endure for 24 hours. In two experiments, we show that induced biases not only persist but survive changes in environmental context, including transferring to different rooms with different experimenters. In one experiment, training and testing materials were also presented in different sensory modalities without significantly reducing the magnitude of the induced bias. Furthermore, we found evidence of changes in emotional vulnerability, congruent with the direction of induced bias, which also persisted for 24 hours. Together with earlier results, these findings show that induced biases generalize over contexts and have persisting emotional consequences, suggesting that appropriately adapted training methods may contribute to developing therapeutic techniques within clinical settings.     

Assessment of deviant arousal in adult male sex offenders with developmental disabilities

Ten individuals, residing in a treatment facility specializing in the rehabilitation of sex offenders with developmental disabilities, participated in an arousal assessment involving the use of the penile plethysmograph. The arousal assessments involved measuring change in penile circumference to various categories of stimuli both appropriate (adult men and women) and inappropriate (e.g., 8- to 9-year-old boys and girls). This approach extends the existing assessment literature by the use of repeated measurement and single-subject experimental design. Data from these assessments were analyzed to determine if clear and informative outcomes were obtained. Overall, three general patterns of results emerged. Some participants showed differentiated deviant arousal or higher levels of arousal to specific inappropriate stimuli (deviant is a term used in the existing sex-offender literature to describe this type of arousal). Other participants showed undifferentiated deviant arousal, in which case they showed nonspecific arousal to inappropriate stimuli. The remaining participants showed no arousal to inappropriate stimuli but did show arousal to appropriate stimuli. Implications for assessment, treatment, and future directions are discussed.     

Attending to affect: appraisal strategies modulate the electrocortical response to arousing pictures

Arousing (unpleasant and pleasant) pictures elicit increased neurophysiological measures of perceptual processing. In particular, the electrocortical late positive potential (LPP) is enhanced for arousing, compared with neutral, pictures. To determine whether the magnitude of the LPP is sensitive to the way stimuli are appraised, 16 participants viewed both pleasant and unpleasant pictures and categorized them along an affective or nonaffective dimension. Results indicate that the LPP was reduced for both pleasant and unpleasant pictures when participants made nonaffective, compared with affective, judgments. These results are consistent with previous studies that have used functional neuroimaging to investigate the role of appraisal on emotional processing. The results are further discussed in terms of the utility of using the LPP to study emotion regulation.     

Reappraisal modulates the electrocortical response to unpleasant pictures

Cognitive strategies such as reappraisal reduce the intensity of negative experience and brain activity that is sensitive to emotional salience. The time course of reappraisal-related neural modulation remains unclear, and it is unknown whether the electrocortical response to emotional stimuli is sensitive to reappraisal. Event-related brain potentials were recorded first while participants passively viewed pleasant, unpleasant, and neutral pictures, and then during an emotion regulation block in which participants were instructed to attend to or reappraise unpleasant pictures. The late positive potential (LPP) was enhanced for pleasant and unpleasant pictures in the passive viewing block, and reappraisal resulted in a reliably reduced LPP—a protracted modulation that began 200 msec after stimulus onset. The degree of LPP modulation was positively related to reductions in the self-reported emotional intensity that followed emotion regulation instructions. These results indicate that reappraisal modulates early electrocortical activity that is related to emotional salience, and that the LPP is a useful tool for studying emotion regulation.     

Child well-being in an era of welfare reform: the sensitivity of transitions in development to policy change

This study examined the age-specific pattern of effects of welfare policies on child achievement. Drawing from 7 random-assignment welfare and antipoverty evaluations that provided more than 30,000 observations of children's achievement, this study found that times of developmental transition are the only periods sensitive to the changes in families brought about by these policies. More specifically, small positive effects of welfare and antipoverty policies were found for children making the transition into middle childhood, and small negative effects of these same policies were found for children making the transition out of middle childhood and into early adolescence. Effects were robust across various program groupings and could not be attributed to family characteristics that differ for children of different ages. This research informs the understanding of how changes in employment and income for low-income parents affect development across childhood.     

Familiarization, attention, and recognition memory in infancy: an event-related potential and cortical source localization study

This study investigated the effects of familiarization and attention on event-related potential (ERP) correlates of recognition memory in infants. Infants 4.5, 6, or 7.5 months of age were either familiarized with 2 stimuli that were used during later testing or presented 2 stimuli that were not used later. Then, infants were presented with a recording of Sesame Street to elicit attention or inattention and presented with familiar and novel stimuli. A negative ERP component over the frontal and central electrodes (Nc) was larger in the preexposure familiarization group for novel- than for familiar-stimulus presentations, whereas the Nc did not differ for the group not receiving a familiarization exposure. Spatial independent components analysis of the electroencephelogram and "equivalent current dipole" analysis were used to examine putative cortical sources of the ERP components. The cortical source of Nc was located in areas of prefrontal cortex and anterior cingulate cortex.     

What is enumerated by subitization mechanisms?

Subitization, the rapid enumeration of small numbers of objects, is often held to reflect a general ability to process three or four items simultaneously. However, questions as to which types of visual representations count as items for subitization have, thus far, received relatively little attention. In several new experiments, we instructed participants to enumerate three or four colored regions in a display. In some trials, all of these regions belonged to separate visual objects, whereas in others, two or more belonged to the same object(s). We found far slower enumeration in the latter case than in the former case, a result that cannot be attributed to Stroop interference from the number of attended objects in a display. We conclude that subitization mechanisms cannot operate on small fragments of shape and color alone, even when such fragments are easily individuated from one another. Rather, such mechanisms are compelled to operate on object representations.     

Amplitude and target diameter in motor programming of discrete, rapid aimed movements: Fitts and Peterson (1964) and Klapp (1975) revisited

The reports by Fitts and Peterson [J. Exp. Psychol. 67(2) (1964) 103-113] and Klapp [J. Exp. Psychol. Hum. Percept. Perform. 104(2) (1975) 147-153] concerning the effects of movement amplitude and target diameter on reaction time present conflicting results. Fitts and Peterson reported that reaction time increased when movement amplitude was lengthened. Klapp reported an interaction in which target diameter effect on reaction time was moderated by movement length: for small targets, reaction time decreased with increasing movement length but reaction time remained unchanged (or increased modestly) when target diameter was large. Two experiments were conducted to replicate and examine the inconsistency in the reaction time results. For both experiments movement time results were in agreement with the predictions of Fitts' law. However, the results for reaction time were mixed: support was obtained for Klapp (1975) but not for Fitts and Peterson (1964). Further analysis identified several potential variables that could have influenced reaction time and explained the different effects on reaction time reported by Fitts and Peterson (1964) and Klapp (1975). The potential variables could include: limb posture at the start of a response; number of limb segments required to perform the task; and the effect of pooling reaction time data from targets located right and left of the start point, and from near and far targets.