Information processing abilities in twins reared apart

A battery of information processing measures and psychometric tests of specific and general cognitive abilities was administered to a sample of 105 individuals which included 34 monozygotic and 13 dizygotic reared apart twin pairs or triplets. Correlations between information processing parameters and psychometric abilities as well as twin resemblances for the information processing parameters were examined. In a principal components analysis of the information processing parameters, three components were identified which accounted for 67% of the total variation; Overall Speed of Response (OSR), Speed of Information Processing (SIP), and Speed of Spatial Processing (SSP). OSR was significantly correlated with WAIS IQ, and psychometric measures of verbal reasoning, spatial ability, and perceptual speed and accuracy. SIP was significantly correlated with WAIS IQ, measures of verbal reasoning, and one of the perceptual speed and accuracy measures. SSP was significantly correlated with measures of both spatial ability and perceptual speed and accuracy. Due to the small size of the dizygotic twin sample, no strong conclusions could be drawn regarding the magnitude of their resemblance. The correlation between component scores of reared apart monozygotic twins was significant for OSR, but not for SIP or SSP.     

Proactive interference plays a role in the word-length effect

The word-length effect is the advantage that lists of short words show over lists of long words in immediate recall. Typically, the word-length effect is used as strong support for decay-based theories of immediate retention. However, the present two experiments show that the traditional word-length effect emerges only after several trials in an experimental session, a result reminiscent of earlier findings in distractor-based short-term forgetting experiments. These results suggest that any complete account of the word-length effect will need to consider a role for proactive interference.     

Regional cerebral glucose metabolism in aphemia: A case report

Local cerebral metabolism was determined in a patient suffering aphemia following cerebral infarction using the 18FDG-PET technique. The syndrome was characterized by profound ictal nonfluency with sparing of other language functions. Speech subsequently improved so that content and grammar were appropriate but mild dysprosody persisted. Conventional CT showed no lesion of the left hemisphere while PET revealed a discrete focus of hypometabolism on the left which partially resolved on serial studies. The metabolic lesion could be localized to the region of the inferior precentral gyrus and the adjacent subcortical space.     

ADHD and Behavioral Inhibition: A Re-examination of the Stop-signal Task

The current study investigates two recently identified threats to the construct validity of behavioral inhibition as a core deficit of attention-deficit/hyperactivity disorder (ADHD) based on the stop-signal task: calculation of mean reaction time from go-trials presented adjacent to intermittent stop-trials, and non-reporting of the stop-signal delay metric. Children with ADHD (n = 12) and typically developing (TD) children (n = 11) were administered the standard stop-signal task and three variant stop-signal conditions. These included a no-tone condition administered without the presentation of an auditory tone; an ignore-tone condition that presented a neutral (i.e., not associated with stopping) auditory tone; and a second ignore-tone condition that presented a neutral auditory tone after the tone had been previously paired with stopping. Children with ADHD exhibited significantly slower and more variable reaction times to go-stimuli, and slower stop-signal reaction times relative to TD controls. Stop-signal delay was not significantly different between groups, and both groups’ go-trial reaction times slowed following meaningful tones. Collectively, these findings corroborate recent meta-analyses and indicate that previous findings of stop-signal performance deficits in ADHD reflect slower and more variable responding to visually presented stimuli and concurrent processing of a second stimulus, rather than deficits of motor behavioral inhibition.     

Stability and change in religiousness during emerging adulthood

Understanding the development of religiousness is an important endeavor because religiousness has been shown to be related to positive outcomes. The current study examined mean-level, rank-order, and individual-level change in females' religiousness during emerging adulthood. Genetic and environmental influences on religiousness and its change and stability were also investigated. Analyses were completed with an epidemiological study of 2 cohorts of twins: 1 assessed at ages 14 and 18 and a 2nd at 20 and 25. Mean levels of religiousness decreased significantly with age, while rank-order stability was high. Individual-level change was also evident. Analyses also supported the hypotheses that more change would occur in the younger cohort compared with the older cohort and that more change would occur in religious service attendance than the general index of religiousness. Twin analyses suggested that the heritability of religiousness increased with age, while the shared environmental influences decreased. For the younger cohort, change was genetic in origin, while stability was environmental. In the older cohort, change was influenced by nonshared environment and stability by both genes and family environment.     

Learning myopia: an adaptive recency effect in category learning

Recency effects (REs) have been well established in memory and probability learning paradigms but have received little attention in category earning research. Extant categorization models predict REs to be unaffected by learning, whereas a functional interpretation of REs, suggested by results in other domains, predicts that people are able to learn sequential dependencies and incorporate this information into their responses. These contrasting predictions were tested in 2 experiments involving a classification task in which outcome sequences were autocorrelated. Experiment 1 showed that reliance on recent outcomes adapts to the structure of the task, in contrast to models' predictions. Experiment 2 provided constraints on how sequential information is learned and suggested possible extensions to current models to account for this learning.     

Perceptions of the parent-adolescent relationship: a longitudinal investigation

A self-report measure of conflict and aspects of warmth in the parent-child relationship was completed by 1,330 11-year-old twins, 1,176 of whom completed the inventory again 3 years later. On average, adolescents' perceptions of the quality of the parent-child relationship declined consistently and moderately between age 11 and age 14. Conflict with parents increased, whereas all aspects of warmth decreased; changes were significantly greater for girls than boys. Variances increased with age, primarily because of increases in the magnitude of genetic effects. Heritability estimates ranged from .09 to .31 at intake and .35 to .45 at follow-up and tended to be higher for boys than girls. Changes in the parent-child relationship are interpreted as reflecting genotype-environment correlation processes whereby adolescents increasingly influence their relationships with their parents.