DNA markers associated with general and specific cognitive abilities

Multivariate quantitative genetic research suggests a hierarchical model of cognitive abilities where genetic effects are largely general, cutting across most cognitive abilities. Some genetic effects, however, are specific to certain cognitive abilities. These results lead to a hypothesis for molecular genetic research: Although most genes associated with one cognitive ability will be related to other cognitive abilities, some genes will be specific to a particular cognitive ability. The current research explored this hypothesis in an analysis of data in specific cognitive abilities from 86 children from 6 to 12 years of age from a larger allelic association study of general cognitive ability. Eight DNA markers were entered simultaneously in separate multiple regression analyses predicting each of four specific cognitive ability factors (Verbal, Spatial, Perceptual Speed, Memory), as well as WISC-R subtest scores. Four marjers (CTGB33, EST00083, HLA, and SOD2) showed similar effects across the cognitive ability scales, suggesting that they are related to general cognitive ability (g). These associations became negligible when the effects of ‘g’ (WISC-R IQ) were removed. Three markers (ADH5, DM, and NGFB) continued to be significantly associated with specific cognitive ability scales after the effects of ‘g’ were removed. Although preliminary, these molecular genetic results support the hierarchical model predicted by quantitative genetic research.     

Form recognition: Individual strategies in multivariate cue utilization

Twenty-five Ss were each presented 1,250 trials in a form-recognition task requiring S to find a form among 25 other forms on each trial. Fifty different eight-sided randomly derived polygons were used as stimuli, each presented in 25 different problems. Factors based on physical measures of the stimuli were correlated with observed latencies using multiple regression to assess cue-utilization strategies, while beta-weight profiles and intercorrelations of the Ss’ predicted latencies were used as indices of individual differences. Multiple correlations of physical-factor scores with observed latencies accounted for a significant proportion of the variance for all Ss, while between-S correlations of predicted latencies were never below .90. By all criteria employed, use of stimulus information was highly consistent among Ss. Replication of the experiment for one S revealed good reliability and nearly identical strategies.     

The role of bigram frequency in the perception of words and nonwords

Memory & Cognition - Adult subjects decided whether strings of four, five, or six letters formed words or nonwords. Words and nonwords were equally probable stimuli, and there were equal...     

Stages of readiness to quit smoking: population prevalence and correlates.

We examined the population prevalence and correlates of stages in smokers' readiness to quit, using data from 1,048 smokers recruited in a self-weighting, multistage, systematic clustered area sample from 0.44% of South Australian dwellings, with an 89% response rate. Smokers in the precontemplation stage comprised 24.1% of the sample, smokers in the contemplation stage comprised 47.2%, and smokers in the preparation stage comprised 28.7%. No sociodemographic variables (i.e., age, sex, marital status, educational level) were found to be significant independent predictors of membership in the different stages. The five significant independent predictors of being in the precontemplation stage (vs. the contemplation stage) were (a) having a higher confidence of quitting, (b) seeing fewer health risks associated with smoking, (c) not having made an attempt to quit, (d) seeing quitting as more difficult, and (e) smoking 25 or more cigarettes a day. The two significant independent predictors of being in the contemplation stage (vs. the preparation stage) were (a) having lower confidence of quitting and (b) not having tried to quit. We discuss implications for the understanding of smoking behavior in populations and also consider how cessation campaigns might address the factors associated with different stages of readiness to quit.     

An investigation into the validity of role play as a procedure for counsellor skill assessment

The aim of this study was to determine the validity of role play as a method for assessing counsellor skill. Video recordings of twelve counsellors' performance in both real and simulated counselling interactions were analysed. Skill assessment included molar ratings of eight skill areas and molecular measures of 28 behaviours. A comparison of counsellor performance between conditions indicated that there was little difference between the real and role-play situations. It is concluded that the modified extended role-play format employed in the present study might be a valid technique for assessment of counselling skills.     

Failure to replicate a QTL association between a DNA marker identified by EST00083 and IQ

In a paper published in this journal, a possible QTL association was reported between general cognitive ability and a marker, identified by an expressed sequence tag, EST00083 (Skuder et al., 1995). In two small samples, the frequency of the common allele of this DNA marker, which was shown to be in the threonine transfer RNA gene in mitochondrial DNA, was significantly greater in a high-IQ group than in a low-IQ group. As part of the ongoing IQ QTL Project (Plomin et al., 1995), we have attempted to replicate this QTL association. First, we found that the QTL association remained significant when we compared 51 high- and 51 -average IQ subjects, drawn in part from the samples used in the previous report. However, when we examined the association in new samples of 40 extremely high-IQ subjects and 50 average-IQ subjects, the association did not replicate. This underlies the need for replication in case-control studies of allelic association.     

Objective and subjective bulimic episodes in the classification of bulimic-type eating disorders: Another nail in the coffin of a problematic distinction

We sought to further explore the validity of the distinction between objective bulimic episodes (OBEs) and subjective bulimic episodes (SBEs) in the study of bulimic-type eating disorders. Drawing on data obtained at the second, interview phase of a large-scale epidemiological study, we identified mutually exclusive subgroups of women with bulimic-type eating disorders who engaged in regular OBEs but not SBEs (n = 37) or regular SBEs but not OBEs (n = 52). These subgroups were compared on a wide range of outcomes, including socio-demographic characteristics, current levels of eating disorder psychopathology, general psychological distress and impairment in role functioning, current and lifetime impairment in quality of life specifically associated with an eating problem, (self)-recognition of an eating problem, health service utilization and use of psychotropic medication. The only difference between groups was that participants who reported regular OBEs were heavier than those who reported regular SBEs. The findings converge with those of previous research in suggesting that bulimic-type eating disorders characterized by regular SBEs, but not OBEs, do not differ in any clinically meaningful way from those characterized by regular OBEs, but not SBEs. Inclusion of bulimic-type eating disorders characterized by regular SBEs as a provisional category requiring further research in DSM-V appears warranted.