Robust Inference for Univariate Proportional Hazards Frailty Regression Models

We consider a class of semiparametric regression models which are one-parameter extensions of the Cox [J. Roy. Statist. Soc. Ser. B 34 (1972) 187-220] model for right-censored univariate failure times. These models assume that the hazard given the covariates and a random frailty unique to each individual has the proportional hazards form multiplied by the frailty. The frailty is assumed to have mean 1 within a known one-parameter family of distributions. Inference is based on a nonparametric likelihood. The behavior of the likelihood maximizer is studied under general conditions where the fitted model may be misspecified. The joint estimator of the regression and frailty parameters as well as the baseline hazard is shown to be uniformly consistent for the pseudo-value maximizing the asymptotic limit of the likelihood. Appropriately standardized, the estimator converges weakly to a Gaussian process. When the model is correctly specified, the procedure is semiparametric efficient, achieving the semiparametric information bound for all parameter components. It is also proved that the bootstrap gives valid inferences for all parameters, even under misspecification. We demonstrate analytically the importance of the robust inference in several examples. In a randomized clinical trial, a valid test of the treatment effect is possible when other prognostic factors and the frailty distribution are both misspecified. Under certain conditions on the covariates, the ratios of the regression parameters are still identifiable. The practical utility of the procedure is illustrated on a non-Hodgkin's lymphoma dataset.Comment: Published by the Institute of Mathematical Statistics (http://www.imstat.org) in the Annals of Statistics (http://www.imstat.org/aos/) at http://dx.doi.org/10.1214/00905360400000053

fMRI biomarkers of social cognitive skills training in psychosis: Extrinsic and intrinsic functional connectivity.

Social cognitive skills training interventions for psychotic disorders have shown improvement in social cognitive performance tasks, but little was known about brain-based biomarkers linked to treatment effects. In this pilot study, we examined whether social cognitive skills training could modulate extrinsic and intrinsic functional connectivity in psychosis using functional magnetic resonance imaging (fMRI). Twenty-six chronic outpatients with psychotic disorders were recruited from either a Social Cognitive Skills Training (SCST) or an activity- and time-matched control intervention. At baseline and the end of intervention (12 weeks), participants completed two social cognitive tasks: a Facial Affect Matching task and a Mental State Attribution Task, as well as resting-state fMRI (rs-fMRI). Extrinsic functional connectivity was assessed using psychophysiological interaction (PPI) with amygdala and temporo-parietal junction as a seed region for the Facial Affect Matching Task and the Mental State Attribution task, respectively. Intrinsic functional connectivity was assessed with independent component analysis on rs-fMRI, with a focus on the default mode network (DMN). During the Facial Affect Matching task, we observed stronger PPI connectivity in the SCST group after intervention (compared to baseline), but no treatment-related change in the Control group. Neither group showed treatment-related changes in PPI connectivity during the Mental State Attribution task. During rs-fMRI, we found treatment-related changes in the DMN in the SCST group, but not in Control group. This study found that social cognitive skills training modulated both extrinsic and intrinsic functional connectivity in individuals with psychotic disorders after a 12-week intervention. These findings suggest treatment-related changes in functional connectivity as a potential brain-based biomarker of social cognitive skills training

EXPLORING ILLUSIONS OF HEIGHT IN SUIT DESIGN

Objective: The goal of this research was to explore how the design of clothing, specifically the design of the suit, can create height illusions. Background: Taller people enjoy many advantages, such as increased income and perceived attractiveness. These advantages motivate people to try to appear taller than they actually are, and clothing experts provide advice on how to accomplish this. However, there is little empirical evidence to validate the illusory effects clothing might have on overall height perception. The few studies that have explored illusions of body size created by clothing design have been limited in two important ways – the test stimuli have included unnatural body shapes and have failed to include naturalistic context (i.e., surrounding depth and size cues available in real scenes). Method: In the first phase, participants (nonexperts in clothing design) provided suggestions for how to appear taller by changing clothes. In the second phase, participants 1) viewed photographs of a variety of targets wearing suit designs that are commonly believed to manipulate viewers’ perceptions of height, 2) rated the targets on traits associated with height such as income and attractiveness, and 3) estimated the heights of these individuals. This study focused on the potential effects of suit color, specifically overall lightness (light vs. dark) and monochromaticity (monochromatic vs. lightness blocking). The effects of these designs were tested with and without contextual information by presenting targets within a natural streetscape or on a white background. Results: In the first phase, we found that nonexperts provided similar suggestions as experts in clothing design, including those pertaining to monochromaticity and lightness. In the second phase, we found that estimates were more accurate with more contextual information, and that clothing can impact height estimations, where monochromatic outfits yielded taller height estimates, although other outfit comparisons did not have effects. Outfits overall did not impact ratings such as income and attractiveness, although estimated height did correlate with these same social attributes. In an exploration of the impact of contextual and target-specific cues other than clothing on height estimations, we found that height perception was potentially dependent on a variety of factors such as the target\u27s race, location (indoors vs. outdoors), stance, and the presence of nearby people. Scientific merit: This study increased our understanding of the conditions under which illusions of size in simple geometric stimuli generalize to the manipulation of size perception in real-world scenes. Broader impact: A better understanding of biases in height perception is relevant to domains in which such estimates are used to identify individuals (e.g., criminal justice) as well as domains in which visual characteristics of individuals are associated with errors in judgments of performance-based merit. (e.g., personnel selection and promotion)

THE EFFECTS OF ALTERNATE-LINE SHADING ON VISUAL SEARCH IN GRID-BASED GRAPHIC DESIGNS

Objective: The goal of this research was to determine whether alternate-line shading (zebra-striping) of grid-based displays affects the strategy (i.e., “visual flow”) and efficiency of serial search. Background: Grids, matrices, and tables are commonly used to organize information. A number of design techniques and psychological principles are relevant to how viewers’ eyes can be guided through such visual works. One common technique for grids, “zebra-striping,” is intended to guide eyes through the design, or “create visual flow” by alternating shaded and unshaded rows or columns. Method: 13 participants completed a visual serial search task. The target was embedded in a grid that had 1) no shading, 2) shading of alternating rows, or 3) shading of alternating columns. Response times and error rates were analyzed to determine search strategy and efficiency. Results: Our analysis found evidence supporting a weak effect of shading on search strategy. The direction of shading had an impact on which parts of the grid were responded to most rapidly. However, a left-to-right reading bias and middle-to-outside edge effect were also found. Overall performance was reliably better when the grid had no shading. Exploratory analyses suggest individual differences may be a factor. Conclusion: Shading seems to create visual flow that is relatively weak compared to search strategies related to the edge effect or left-to-right reading biases. In general, however, the presence of any type of shading reduced search performance. Application: Designers creating a grid-based display should not automatically assume that shading will change viewers search strategies. Furthermore, although strategic shading may be useful for tasks other than that studied here, our current data indicate that shading can actually be detrimental to visual search for complex (i.e., conjunctive) targets