Dopamine and the origins of human intelligence

A general theory is proposed that attributes the origins of human intelligence to an expansion of dopaminergic systems in human cognition. Dopamine is postulated to be the key neurotransmitter regulating six predominantly left-hemispheric cognitive skills critical to human language and thought: motor planning, working memory, cognitive flexibility, abstract reasoning, temporal analysis/sequencing, and generativity. A dopaminergic expansion during early hominid evolution could have enabled successful chase-hunting in the savannas of sub-Saharan Africa, given the critical role of dopamine in counteracting hyperthermia during endurance activity. In turn, changes in physical activity and diet may have further increased cortical dopamine levels by augmenting tyrosine and its conversion to dopamine in the central nervous system (CNS). By means of the regulatory action of dopamine and other substances, the physiological and dietary changes may have contributed to the vertical elongation of the body, increased brain size, and increased cortical convolutedness that occurred during human evolution. Finally, emphasizing the role of dopamine in human intelligence may offer a new perspective on the advanced cognitive reasoning skills in nonprimate lineages such as cetaceans and avians, whose cortical anatomy differs radically from that of primates.     

多巴胺对动物冲动性的影响

冲动性是注意缺陷障碍、物质成瘾以及病理性赌博等常见精神疾病的主要症状, 已经成为人们日益关注的焦点。研究发现, 前额叶–纹状体神经回路多巴胺参与了冲动性的调节, 但是研究结果并不一致, 多巴胺在冲动性中发挥的作用, 可能会受到三个不同因素的影响。首先, 冲动性具有多维度特征, 多巴胺对冲动的多种亚结构的作用存在差异; 其次, 多巴胺可以通过多个脑区以及与其他递质系统的交互作用影响冲动性; 最后, 多巴胺在调节冲动性的过程中可能还受到多种变量的影响, 如个体差异、环境线索等。     

Closely observed texts

This paper discusses a central theme of the novel What Maisie Knew by Henry James, namely the development of a child's consciousness and internal world in a hostile psychological environment. It explores the way in which the novel dramatizes the problems for a child, in such circumstances, of knowing and understanding her own experience and the adult world. The paper charts the difficulties for Maisie in negotiating a child's ordinary tasks and stages of psychic growth, and in particular the Oedipal situation. It also explores the parallel in the novel between the child's attempts to know and the attempts of the reader of fiction to know, and the use of reading as a metaphor for perception and learning.     

Blocking observed in human eyelid conditioning

The status of blocking in human eyelid conditioning was examined in a series of four experiments modelled on rabbit nictitating membrane (NMR) procedures to ensure comparability with the animal literature. The first three employed Tones and Lights as CSs and a preliminary experiment established equivalent salience of these stimuli. The fourth employed all light conditioned stimuli (CSs). Each of the experiments balanced order of presentation of blocked and non-blocked stimuli in extinction; each yielded reliable evidence of blocking tested in extinction. However, the blocking effects were attenuated or abolished in those groups receiving the to-be-blocked stimulus on the first trial in extinction. The results show blocking to be a relatively weak, easily disrupted phenomenon compared with rabbit studies. They suggest that rapid re-appraisal of stimulus significance plays a more important role in human subjects than has been observed in animal studies.     

Blocking observed in human eyelid conditioning

Four eyelid conditioning experiments designed to be comparable to rabbit nictitating membrane (NMR) studies examined the blocking phenomenon in humans. All experiments utilized a within-subjects design, with Stage 1 of discrimination, Stage 2 of compound training, and a final test stage comparing responding to the blocked and non-blocked CSs. In two of the experiments (1 and 4) the comparison was made within subjects over all extinction trials. In Experiment 3 the test phase consisted of further reinforced training of the blocked and non-blocked CSs. These three experiments produced evidence of blocking when all extinction trials were entered into the analysis. Experiment 2, which involved a between-subjects comparison, failed to demonstrate the blocking effect. Wide variability both between and within subjects obscured the experimental effects. Post-experimental questionnaires designed to assess awareness of stimulus relations failed to identify a subjective blocking effect and showed no relationship to conditioned eyelid responding     

Trait Extraversion and Dopamine Function

An influential theory within personality neuroscience suggests that trait extraversion is underpinned by individual differences in dopamine function. In a review of the relevant literature, we evaluate this theory in light of the evidence from molecular genetics, neuroimaging, and psychopharmacology. Evidence linking individual differences in extraversion with dopamine‐relevant genes, structural volume of dopamine‐rich brain regions (e.g., in striatal and ventral prefrontal areas), dopamine receptor availability, and frontal alpha asymmetry is mixed at best. Evidence concerning both scalp recorded (electroencephalogram) and hemodynamic (functional magnetic resonance imaging) neural responses to rewards appears somewhat more promising. Perhaps the best evidence concerns extraversion‐dependent responses – both neural and behavioural – to dopaminergic drugs. Future research in this area must go beyond the demonstration of theoretically consistent associations and attempt to provide more specific causal evidence for the dopamine hypothesis of extraversion. A further challenge is to expand this hypothesis to incorporate other neurobiological processes that are likely to underlie this trait.     

Configural-like effects observed in the course of second-order conditioning in rats

After receiving first-order CER (conditioned emotional response) conditioning, four groups of rats were exposed to the first-order conditioned stimulus (CS₁) and a new stimulus (CS₂) according to one of three paradigms. For different groups, CS₂ preceded CS₁, was simultaneously compounded with it, or was explicitly unpaired with it. There was evidence of second-order conditioning (SOC) only when CS₂ preceded CS₁, with the effect diminishing when SOC training was continued for a long time. Though suppression to CS₁ extinguished in the course of SOC training, animals which had experienced CS₂ preceding CS₁ suppressed almost completely when later tested with CS₁ alone. This “protection-from-extinction” is formally similar to an analogous effect observed in the simultaneous compound group. Animals appear to “configure” elements of both simultaneous and successive compounds.     

Inventoried and observed stress in parent-child interactions

It has been hypothesized that parental stress results in poor parent-child interactions. However, this has not been adequately researched due to the difficulty in measuring and quantifying parenting stress and parent-child interaction quality. Two measures were employed in the present study to evaluate the parent-child relationship. The Marschak Interaction Method (MIM) was used to provide a context in which to assess the quality of parent-child interactions, and the Parenting Stress Index (PSI) was used as a measure of stress in the family system. The present study (1) developed a standardized behavioral rating system for the MIM, (2) tested 46 parent-child dyads with the MIM and PSI, and (3) assessed which subscales of the PSI were the best predictors of parent-child behavior observed during the MIM. Parents reporting more stress on the PSI were rated as displaying significantly lower quality (more negative) parentchild interactions. In addition, parents’ socioeconomic status accounted for 65 % of the variance, and parental stress accounted for an additional 9% of the variance, in MIM behavior ratings.     

Hand dominance influences the processing of observed bodies

In motor tasks, subgroups of lefthanders have been shown to differ in the distribution of attention about their own bodies. The present experiment examined whether similar attentional biases also apply when processing observed bodies. Sixteen right handers (RHs), 22 consistent left handers (CLHs) and 11 relatively ambidextrous inconsistent left handers (ILHs) performed an own body transformation task in which they were instructed to make speeded left–right judgements about a schematic human figure. Attentional biases associated with handedness were found to extend to observed bodies: CLHs’ judgements were faster to the figure’s left side, while ILHs, like RHs, showed facilitated performance to the figure’s right side. These results demonstrate a novel embodiment effect whereby the processing of a static schematic human figure is modulated by an individual’s personal motor capabilities. This finding suggests that motor simulation may contribute to whole body perception in the absence of actual or implied actions.     

Quantitative measurement of observed workload in the analysis of aircrew performance

A methodology for the quantitative evaluation of observed workload was proposed. The model was designed to provide point estimations of observed workload at any time during the performance of a set of tasks. The model was also designed to provide information about the task-scheduling strategies used to complete a set of tasks. The proposed model was then tested with data from a full mission flight simulation. The model predictions correlated significantly with expert ratings of workload management made during the flight simulation. The model was also able to distinguish between low- and high-performing aircrews when performance was based on the number of errors made during flight simulations.     

Dopamine D1 receptors in the anterior cingulate cortex regulate effort-based decision making

The anterior cingulate cortex (ACC) has been implicated in encoding whether or not an action is worth performing in view of the expected benefit and the cost of performing the action. Dopamine input to the ACC may be critical for this form of effort-based decision making; however, the role of distinct ACC dopamine receptors is yet unknown. Therefore, we examined in rats the effects of an intra-ACC D1 and D2 receptor blockade on effort-based decision making tested in a T-maze cost-benefit task. In this task, subjects could either choose to climb a barrier to obtain a high reward in one arm or a low reward in the other arm without a barrier. Unlike vehicle-treated rats, rats with intra-ACC infusion of the D1 receptor antagonist SCH23390 exhibited a reduced preference for the high-cost- high-reward response option when having the choice to obtain a low reward with little effort. In contrast, in rats with intra-ACC infusion of the D2 receptor antagonist eticlopride, the preference for the high-cost-high-reward response option was not altered relative to vehicle-treated rats. These data provide the first evidence that D1 receptors in the ACC regulate effort-based decision making.     

Errors in subtractions: judged and observed frequencies

In a first study 10 adults, aged 24-44 years, solved all 105 subtraction problems in the form M - N = , where 0 < or = M < or = 13, 0 < or = N < or = 13 and N < or = M. Each participant solved every problem 10 times and in total there were 10 500 answers. Answers, response latencies and errors were registered. Retrospective verbal reports were also given, indicating how a solution was reached: (1) via a (conscious) reconstructive cognitive process or (2) via an (unconscious) reproductive (retrieval) process. The participants made 291 errors (2.8%) when solving the subtractions in study 1. The rate of self-correction was very high, 92%. In a second study 27 undergraduate students estimated overall error rates, including self-corrected errors for the 105 subtraction problems used in the first study. Judged and actual error rates were compared. The participants systematically underestimated error rates for error prone problems and overestimated error rates for error free problems. The participants were fairly accurate when they predicted problems that were most error prone, with a hit rate of 0.67 for the (18) problems predicted as the most error prone ones. In contrast, predictions of which problems were error free were very poor with a hit rate of only 0.20 of the problems predicted as error free really having no errors in study 1. The correlation between judged error rates and frequencies for actually made errors was 0.69 for answers belonging to reconstructive solutions. In contrast, there was no significant correlation between judged and actual error rates at all for retrieved solutions, possibly reflecting the inaccessibility to consciousness of quick retrieval processes.     

Factor structure in groups selected on observed scores

A new method is proposed for estimating factor means and factor covariances in a group of individuals selected on their observed scores. The selection variable is, for example, the total score on an admissions test. Given a factor model for the test items based on the group of test takers, we may be interested in the factor structure for those in the top quartile. The differences in factor means and covariances between this selected group and the full group gives useful information both on successful test performance and on test validity. The new method draws on the classic Pearson-Lawley selection formulas. It avoids the fallacy of factor analysis on the selected group, which would lead to incorrect estimates. The new method is applied to a simple factor structure model for the GMAT test. Although the majority of the GMAT items test verbal skills, it is found that a quantitative factor shows the greatest change in moving from average to top quartile test takers.