Association of biochemical and subjective indicators of drinking habits with performance on different neurobehavioral tasks

The present paper outlines the association of biochemical and subjective indicators of alcohol consumption. Due to its relevance as a potential confounding variable in occupational neurotoxicology, both sources of information about drinking habits were related to neurobehavioral test performance. A sample of 308 rotogravure printers and control subjects from a cross-sectional longitudinal study in various German printing plants was studied. Duration of employment was 4 months to 44 years (mean = 14.9, sd = 9.67). Mean age was 38.4 years (range 21 - 60). From venous blood samples three parameters considered to be sensitive for increased consumption of alcohol were used. They were carbohydrate-deficient transferrin (CDT), gamma glutamyl transferase (GGT), and mean cell volume (MCV). During the medical interview subjects with any chronic liver disease were identified and excluded from data analysis. Additionally, information about weekly consumption of alcohol was assessed and transformed to grams per day (g/d) values. Neurobehavioral testing included simple reaction time (SPES version), switching attention, symbol digit substitution, and digit span (EURONEST version). Additionally, a questionnaire of neurotoxic complaints was administrated. Other covariates, i.e. verbal ability, history of solvent exposure, and age were controlled. GGT and CDT were elevated in 10.5% and 6.6% of the population. 3.5% of the subjects reported daily consumption higher than 60 gram. There were positive correlations of CDT and GGT with the subjective indicator of drinking habits. The magnitude of these relationships were low, but the associations were significant. MCV was not correlated with subjective reports of drinking habits, but it showed convergent correlations with CDT and GGT. Comparison of these two parameters with performance on neurobehavioral tasks yielded only one negative association, i.e. between the memory-loaded tasks factor and GGT. CDT and subjective estimation of alcohol consumption were not related to any cognitive function tested in this study. Especially, the digits-backward task was negatively correlated with increased GGT.     

Biomechanical analysis of masticatory system configuration in Neandertals and Inuits

Johnson-Laird and Byrne (1991) present a theory of conditional inference based upon the manipulation of mental models. In the present paper, the theory is critically examined with regard to its ability to account for psychological data, principally with respect to the rate at which people draw the four basic inferences of modus ponens (MP), denial of the antecedent (DA), affirmation of the consequent (AC) and modus tollens (MT). It is argued first that the theory is unclear in its definition and in particular with regard to predictions of problem difficulty. Clarification and specification of principles are consequently provided here. Next, it is argued that there are a number of phenomena in the conditional reasoning literature for which the theory cannot account in its present form. Specifically, (a) the relatively frequency of DA and AC inferences on affirmative conditional is not as predicted by the theory, (b) differences occur between inferences on if then and only if rules beyond the capacity of the theory to explain and (c) there is no account of the "negative conclusion bias" observed when negated components are introduced into the rules. A number of revisions to the mental model theory of conditional reasoning are proposed in order to account for these findings.