When effect sizes disagree: the case of r and d

The increased use of effect sizes in single studies and meta-analyses raises new questions about statistical inference. Choice of an effect-size index can have a substantial impact on the interpretation of findings. The authors demonstrate the issue by focusing on two popular effect-size measures, the correlation coefficient and the standardized mean difference (e.g., Cohen's d or Hedges's g), both of which can be used when one variable is dichotomous and the other is quantitative. Although the indices are often practically interchangeable, differences in sensitivity to the base rate or variance of the dichotomous variable can alter conclusions about the magnitude of an effect depending on which statistic is used. Because neither statistic is universally superior, researchers should explicitly consider the importance of base rates to formulate correct inferences and justify the selection of a primary effect-size statistic.     

Incremental validity analyses of the violence risk appraisal guide and the psychopathy checklist: screening version in a civil psychiatric sample

This study compares two instruments frequently used to assess risk for violence, the Violence Risk Appraisal Guide (VRAG) and the Psychopathy Checklist: Screening Version (PCL:SV), in a large sample of civil psychiatric patients. Despite a strong bivariate relationship with community violence, the VRAG could not improve on the predictive validity of the PCL:SV alone, even though the VRAG includes several ostensible violence risk factors other than psychopathy. Moreover, incremental validity analyses indicated that the remaining VRAG items accounted for little or no variance in violent outcomes once psychopathy scores were controlled. Conversely, the PCL:SV continued to account for considerable variance after controlling for the VRAG. These results reflect the limited validity of the VRAG items in civil psychiatric samples beyond the variance that is explained by the PCL:SV alone.     

Harm, intent, and the nature of aggressive behavior: measuring naturally occurring aggression in barroom settings

The research goals were to use the constructs of harm and intent to quantify the severity of aggression in the real-world setting of the bar/club, to describe the range of aggressive behaviors and their relationship to harm and intent, and to examine gender differences in the form and severity of aggression. Systematic observations were conducted by trained observers on 1,334 nights in 118 bars/clubs. Observers documented a range of aggressive acts by 1,754 patrons in 1,052 incidents, with many forms of aggression occurring at more than one harm and intent level. Women used different forms of aggression, inflicted less harm, and were more likely to have defensive intent compared with men. Implications of the findings for research and measurement of aggression and applications to preventing aggression and violence are discussed.     

The development of landmark and beacon use in young children: evidence from a touchscreen search task

Children ages 2, 3 and 4 years participated in a novel hide-and-seek search task presented on a touchscreen monitor. On beacon trials, the target hiding place could be located using a beacon cue, but on landmark trials, searching required the use of a nearby landmark cue. In Experiment 1, 2-year-olds performed less accurately than older children on landmark trials but performed equivalently on beacon trials. In Experiment 2, the number of items on the screen was reduced and 2-year-olds' performance improved. Use of the landmark transformation technique in Experiment 3 revealed that older children formed a more precise landmark-target spatial relationship than 2-year-olds. Experiment 4 showed that the transformation itself was not responsible for the youngest participants' decreased accuracy in Experiment 3. Overall, beacons were utilized effectively by all participants, but the use of landmark cues is refined between the ages of 2 and 4.     

The supplementary motor area in motor and perceptual time processing: fMRI studies

The neural bases of timing mechanisms in the second-to-minute range are currently investigated using multidisciplinary approaches. This paper documents the involvement of the supplementary motor area (SMA) in the encoding of target durations by reporting convergent fMRI data from motor and perceptual timing tasks. Event-related fMRI was used in two temporal procedures, involving (1) the production of an accurate interval as compared to an accurate force, and (2) a dual-task of time and colour discrimination with parametric manipulation of the level of attention attributed to each parameter. The first study revealed greater activation of the SMA proper in skilful control of time compared to force. The second showed that increasing attentional allocation to time increased activity in a cortico-striatal network including the pre-SMA (in contrast with the occipital cortex for increasing attention to colour). Further, the SMA proper was sensitive to the attentional modulation cued prior to the time processing period. Taken together, these data and related literature suggest that the SMA plays a key role in time processing as part of the striato-cortical pathway previously identified by animal studies, human neuropsychology and neuroimaging.     

Adolescent and parent perceptions of media influence on adolescent sexuality

Empirical evidence suggests that television and other media influence adolescents' attitudes and behaviors. Much of the research in this area is based on surveys in which adolescents are asked to rank the relative importance of a fixed set of factors such as parents, peers, and media. We reviewed data from focus groups conducted with adolescents and their parents to examine the extent to which adolescents identify--without prompting--media as a source of influence on sexual behavior. Adolescents seemed indifferent to media influence (e.g., media influence was mentioned in only one adolescent focus group), but their parents expressed significant concern about media influence. Future research should investigate the extent to which influences exist outside of adolescents' consciousness. For now, parents and sexuality educators may need to convince adolescents that concerns about the media are valid before trying to change media-influenced behavior.     

Stages of change in anxiety: psychometric properties of the University of Rhode Island Change Assessment (URICA) scale

Readiness for change is increasingly cited as an important variable in the health behaviours literature, yet there remains a dearth of research related to this construct in mental health. This study examined the psychometric properties of the University of Rhode Island Change Assessment (URICA) scale in two samples. In Study 1 (n = 252), undergraduates completed the URICA and were administered measures of hopelessness, the consequences of worry, self-esteem, anxious symptomatology, and social desirability. The reliability and validity of the URICA were generally supported, although the goodness-of-fit with the intended subscales was only moderate. The Precontemplation, Contemplation and Maintenance subscales correlated as expected with ancillary measures, but the Action subscale did not. In Study 2 (n = 81), individuals with panic disorder were administered the URICA at initial assessment and following cognitive behavioural therapy. The URICA demonstrated excellent reliability, significantly predicted treatment retention and dropout, and showed modest utility for predicting treatment outcome. Confirmatory factor analysis, however, revealed an inadequate fit to the intended subscales. The implications of these findings are discussed and directions for future research highlighted.     

Reexamining the vocabulary spurt

The authors asked whether there is evidence to support the existence of the vocabulary spurt, an increase in the rate of word learning that is thought to occur during the 2nd year of life. Using longitudinal data from 38 children, they modeled the rate of word learning with two functions, one with an inflection point (logistic), which would indicate a spurt, and one without an inflection point (quadratic). Comparing the fits of these two functions using likelihood ratios, they found that just 5 children had a better logistic fit, which indicated that these children underwent a spurt. The implications for theories of cognitive and language development are considered.