An object-oriented simulation of a brain system underlying human aggression

Neural structures involved in aggression were incorporated into a model on the basis of neuro-anatomical data. A software program written in Smalltalk, the Brain Structure Simulator (Seguin, 1994) was used to simulate the effects of activity levels of different brain structures. Relationships among brain structures were then tested by changing activity levels of key structures. Results were consistent with research reports on the brain basis of aggression (Albert, Walsh, & Jonik, 1993; Pontius, 1984).     

Is visual attention automatically attracted by one’s own name?

Subjects were presented with briefly exposed visual displays of words that were common first names with a length of four to six letters. In the main experiment, each display consisted of four words: two names shown in red and two shown in white. The subject’s task was to report the red names (targets), but ignore the white ones (distractors). On some trials the subject’s own name appeared as a display item (target or distractor). Presentation of the subject’s name as a distractor caused no more interference with report of targets than did presentation of other names as distractors. Apparently, visual attention was not automatically attracted by the subject’s own name.     

Reducing MMPI-2 defensiveness: the effect of specialized instructions on retest validity in a job applicant sample

The MMPI-2 is often used for screening job applicants when public safety or security are at risk. Inherent in such applications is concern for profile validity and test defensiveness. In this study, we examine the impact of revised instructions on profile validity for a group of job applicants who initially produced invalid profiles. Participants were 271 male applicants for airline pilot positions. Of these, 72 produced invalid defensive MMPI-2 profiles during preemployment screening. The MMPI-2 was readministered to these applicants with instructions informing them of validity scales and instructing them to respond in a more open, honest manner. Comparisons were made between valid and invalid profiles for initial administrations and between valid and invalid profiles at readministration. Some clinical scales were more elevated for valid, nondefensive profiles. Most content scales showed more elevation for valid profiles, and 12% of the applicants who were retested produced significant elevations (T>or=65) on the content scales. Profiles were similar to those produced by employed pilots of a previous study.     

Reading performance and general cognitive ability in twins with reading difficulties and control pairs

The etiology of the observed relationship between general cognitive ability and reading performance was investigated by analyzing data from samples of twin pairs tested in the Colorado Learning Disabilities Research Center. Bivariate phenotypic and genetic structural equation models were fitted to data from 486 twin pairs selected for reading deficits (276 identical and 210 same-sex fraternal) and 314 control pairs (195 identical and 119 same-sex fraternal). Subtests of the Peabody Individual Achievement test (Reading Recognition, Reading Comprehension, and Spelling) were used as measures of reading performance, and verbal and performance IQ scores from the Wechsler Intelligence Scale for Children-Revised (WISC-R) or Wechsler Adult Intelligence Scale-Revised (WAIS-R) were used as indices of general cognitive ability. The results of these confirmatory factor analyses indicate that shared environmental influences do not contribute significantly to covariation between general cognitive ability and reading performance. In contrast, genetic influences contribute substantially to the relationship between the two latent factors. Moreover, the genetic and phenotypic variances of reading performance in the proband group are larger than those in controls, whereas both the genetic and phenotypic correlations between reading performance and general cognitive ability are lower in probands. These results are consistent with recent reports that reading disability may be caused by one or more genes with major effects.     

The dimensionality of the flanker compatibility effect: A psychophysiological analysis

The psychophysiological approach was used to evaluate the effects of feature similarity and intrinsic response mapping on the flanker compatibility effect. Symbol (e.g., < > < and < / <) and letter arrays (e.g., HCH and SCS) were used. Results showed that delays in stimulus evaluation and both peripheral and central response competition contributed to the compatibility effect, with the contribution of these processes depending on feature similarity and the intrinsic response mapping of the stimuli. For letter stimuli, the difference in the size of the compatibility effect for similar and dissimilar arrays could be accounted for in terms of stimulus evaluation. For symbol arrays, differences in size of the compatibility effect could be accounted for by response competition. Thus, symbol and letter arrays do not appear to be processed differently; what is different is the degree to which stimulus and response-related processes are affected by incompatibility.     

Food-deprivation effects on punished schedule-induced drinking in rats.

Food-deprived rats (at 80% of their free-feeding weights) were exposed to a fixed-time 60-s schedule of food-pellet presentation and developed schedule-induced drinking. Lick-dependent signaled delays (10 s) to food presentation led to decreased drinking, which recovered when the signaled delays were discontinued. A major effect of this punishment contingency was to increase the proportion of interpellet intervals without any licks. The drinking of yoked control rats, which received food at the same times as those exposed to the signaled delay contingency (masters), was not consistently reduced. When food-deprivation level was changed to 90%, all master and yoked control rats showed decreases in punished or unpunished schedule-induced drinking. When the body weights were reduced to 70%, most master rats increased punished behavior to levels similar to those of unpunished drinking. This effect was not observed for yoked controls. Therefore, body-weight loss increased the resistance of schedule-induced drinking to reductions by punishment. Food-deprivation effects on punished schedule-induced drinking are similar to their effects on food-maintained lever pressing. This dependency of punishment on food-deprivation level supports the view that schedule-induced drinking can be modified by the same variables that affect operant behavior in general.     

Controlling the Ground Reaction Force During Lifting

The control of the ground reaction force vector relative to the center of gravity (CoG) was examined while subjects performed a back-lifting task. Six male subjects (aged 24.0 +/- 2.5 years) repeatedly lifted a barbell. A biomechanical analysis that used a linked segment model revealed that the summed rotations of body segments during lifting yielded a specific rate of change of the angular momentum of the entire body. This equaled the external moment provided by Fsubg; relative to CoG. This implies that multisegment movements involve control of the angular momentum of the entire body through an appropriately directed Fsubg;. Thus, in dynamic tasks Fsubg; is pointed away from rather than lined up with the CoG, as is the case in static tasks.     

A general linear model for estimating effect size in the presence of publication bias

When the process of publication favors studies with smallp-values, and hence large effect estimates, combined estimates from many studies may be biased. This paper describes a model for estimation of effect size when there is selection based on one-tailedp-values. The model employs the method of maximum likelihood in the context of a mixed (fixed and random) effects general linear model for effect sizes. It offers a test for the presence of publication bias, and corrected estimates of the parameters of the linear model for effect magnitude. The model is illustrated using a well-known data set on the benefits of psychotherapy.Authors' note: The contributions of the authors are considered equal, and the order of authorship was chosen to be reverse-alphabetical.