An optimization approach for mapping and measuring the divergence and correspondence between paths

Many domains of empirical research produce or analyze spatial paths as a measure of behavior. Previously, approaches for measuring the similarity or deviation between two paths have either required timing information or have used ad hoc or manual coding schemes. In this paper, we describe an optimization approach for robustly measuring the area-based deviation between two paths we call ALCAMP (Algorithm for finding the Least-Cost Areal Mapping between Paths). ALCAMP measures the deviation between two paths and produces a mapping between corresponding points on the two paths. The method is robust to a number of aspects in real path data, such as crossovers, self-intersections, differences in path segmentation, and partial or incomplete paths. Unlike similar algorithms that produce distance metrics between trajectories (i.e., paths that include timing information), this algorithm uses only the order of observed path segments to determine the mapping. We describe the algorithm and show its results on a number of sample problems and data sets, and demonstrate its effectiveness for assessing human memory for paths. We also describe available software code written in the R statistical computing language that implements the algorithm to enable data analysis.     

Effects of practice on variability, effects of variability on transfer

Five experiments examined how practice early in skill acquisition affected variability and accuracy during skill retention (Experiments 1-5) and skill transfer (Experiments 3, 4, 5). Lag constraints required that each path from apex to base of a computer-generated pyramid display differ from some number (the lag) of immediately prior paths. Location constraints specified end points at which paths must exit the pyramid. In all experiments, an early optimal period for acquiring a variability level was identified. Both low and high levels of variability were sustained during retention; high levels facilitated transfer. The results suggest that (a) early practice that requires high variability sensitizes learners to changes in condition and (b) such perception-performance links facilitate transfer by activating appropriate alternative strategies/schema or initiating their construction.     

Children's use of geometry for reorientation

Research on navigation has shown that humans and laboratory animals recover their sense of orientation primarily by detecting geometric properties of large-scale surface layouts (e.g. room shape), but the reasons for the primacy of layout geometry have not been clarified. In four experiments, we tested whether 4-year-old children reorient by the geometry of extended wall-like surfaces because such surfaces are large and perceived as stable, because they serve as barriers to vision or to locomotion, or because they form a single, connected geometric figure. Disoriented children successfully reoriented by the shape of an arena formed by surfaces that were short enough to see and step over. In contrast, children failed to reorient by the shape of an arena defined by large and stable columns or by connected lines on the floor. We conclude that preschool children's reorientation is not guided by the functional relevance of the immediate environmental properties, but rather by a specific sensitivity to the geometric properties of the extended three-dimensional surface layout.     

With a little help from my cross-group friend: reducing anxiety in intergroup contexts through cross-group friendship

The authors induced cross-group friendship between Latinos/as and Whites to test the effects of cross-group friendship on anxiety in intergroup contexts. Cross-group friendship led to decreases in cortisol reactivity (a hormonal correlate of stress; W. R. Lovallo & T. L. Thomas, 2000) over 3 friendship meetings among participants high in race-based rejection sensitivity (R. Mendoza-Denton, G. Downey, V. J. Purdie, A. Davis, & J. Pietrzak, 2002) and participants high in implicit prejudice (A. G. Greenwald, B. A. Nosek, & M. R. Banaji, 2003). Cross-group partners' prior intergroup contact moderated the relationship between race-based rejection sensitivity and cortisol reactivity. Following the manipulation, participants kept daily diaries of their experiences in an ethnically diverse setting. Implicitly prejudiced participants initiated more intergroup interactions during the diary period after making a cross-group friend. Participants who had made a cross-group friend reported lower anxious mood during the diary period, which compensated for greater anxious mood among participants high in race-based rejection sensitivity. These findings provide experimental evidence that cross-group friendship is beneficial for people who are likely to experience anxiety in intergroup contexts.     

Characterization and sociocultural predictors of neuropsychological test performance in HIV+ Hispanic individuals

Hispanic individuals in the U.S. have been disproportionately impacted by HIV/AIDS, yet little is known regarding the neuropsychological sequelae of HIV within the Hispanic population. This study characterized neuropsychological (NP) test performance of HIV+ English-speaking Hispanic participants (n = 51) and investigated the combined roles of sociocultural factors (e.g., ethnicity, socioeconomic status [SES] proxy, and reading level) on NP test performance among our HIV+ Hispanic and non-Hispanic White participants (n = 49). Results revealed that the pattern of NP impairment in HIV+ Hispanic participants is consistent with the frontal-striatal pattern observed in HIV-associated CNS sequelae, and the overall prevalence of global NP impairment was high compared to previous reports with more ethnically homogeneous, non-Hispanic White cohorts. Multivariate prediction models that considered both sociocultural factors and CD4 count revealed that reading level was the only unique predictor of global NP functioning, learning, and attention/working memory. In contrast, ethnicity was the only unique predictor of abstraction/executive functioning. This study provides support for the use of neuropsychological evaluation in detecting HIV-associated NP impairment among HIV+ Hispanic participants and adds to the growing literature regarding the importance of considering sociocultural factors in the interpretation of NP test performance.     

Distribution of Spatial Visualization and Mathematical Problem Solving Scores: A Test of Stafford's X-linked Hypotheses

This study investigated distribution of spatial visualization scores (Space Relations test of the Differential Aptitude Test) and mathematical problem solving scores (Mental Arithmetic Problems) obtained by 161 male and 152 female, 9th grade, white students for fit to the distributions predicted by the X-linked hypotheses of recessive inheritance of these skills. Data did not support the X-linked hypotheses. No significant sex-related differences were found between mean scores of tests of spatial visualization or mathematical problem solving.