The virgil role

The referral of a patient for subspecialty consultation and examination is but one facet of the primary care physician's involvement with his patient. Using examples from my practice, I argue that the term "gatekeeper" is an inadequate term for describing what the primary care physician does, or should do, for his patient. "Virgil Role" is offered as an alternative expression based on a proposed parallel between Dante's passage through the Inferno accompanied by his mentor-guide, Virgil, and a sick person's journey through his personal Hell of illness and the labyrinthine medical care system, guided by his physician.     

Effect analysis and causation in linear structural equation models

This paper considers total and direct effects in linear structural equation models. Adopting a causal perspective that is implicit in much of the literature on the subject, the paper concludes that in many instances the effects do not admit the interpretations imparted in the literature. Drawing a distinction between concomitants and factors, the paper concludes that a concomitant has neither total nor direct effects on other variables. When a variable is a factor and one or more intervening variables are concomitants, the notion of a direct effect is not causally meaningful. Even when the notion of a direct effect is meaningful, the usual estimate of this quantity may be inappropriate. The total effect is usually interpreted as an equilibrium multiplier. In the case where there are simultaneity relations among the dependent variables in tghe model, the results in the literature for the total effects of dependent variables on other dependent variables are not equilibrium multipliers, and thus, the usual interpretation is incorrect. To remedy some of these deficiencies, a new effect, the total effect of a factorX on an outcomeY, holding a set of variablesF constant, is defined. When defined, the total and direct effects are a special case of this new effect, and the total effect of a dependent variable on a dependent variable is an equilibrium multiplier.For helpful comments, I am grateful to G. Arminger, K. Bollen, W. Faris, R. m. Hauser, T. Petersen, three anonymous Psychometrikas reviewers, and the Editor. For computational assistance, I am grateful to B. D. Kim.     

Reach tracking reveals dissociable processes underlying inhibitory control in 5‐ to 10‐year‐olds and adults

Researchers have proposed that two processes featuring distinct types of inhibition support inhibitory control: a response threshold adjustment process involving the global inhibition of motor output and a conflict resolution process involving competitive inhibition among co‐active response alternatives. To target the development of these processes, we measured the reaching behavior of 5‐ to 10‐year‐olds (Experiment 1) and adults (Experiment 2) as they performed an Eriksen flanker task. This method provided two key measures: initiation time (the time elapsed between stimulus onset and movement onset) and reach curvature (the degree to which a movement deviates from a direct path to the selected target). We suggest that initiation time reflects the response threshold adjustment process by indexing the degree of motoric stopping experienced before a movement is started, while reach curvature reflects the conflict resolution process by indexing the degree of co‐activation between response alternatives over the course of a movement. Our results support this claim, revealing different patterns effects in initiation time and curvature, and divergent developmental trajectories between childhood and adulthood. These findings provide behavioral evidence for the dissociation between global and competitive inhibition, and offer new insight into the development of inhibitory control.     

Reversing how to think about ambiguous figure reversals: spontaneous alternating by uninformed observers

Ambiguous figures are a special class of images that can give rise to multiple interpretations. Traditionally, switching between the possible interpretations of an ambiguous figure, or reversing one's interpretation, has been attributed either to top-down or to bottom-up processes (e.g. attributed to having knowledge of the nature of the ambiguity, or to a form of neuronal fatigue). Here we present evidence that is incompatible with both forms of explanations. Observers aged 5-9 years can reverse ambiguous figures when uninformed about the ambiguity, negating purely top-down explanations. Further, those children who make these 'spontaneous' reversals are more likely to succeed on a high-order theory-of-mind task, negating purely bottom-up explanations.     

A theory of causal learning in children: causal maps and Bayes nets

The authors outline a cognitive and computational account of causal learning in children. They propose that children use specialized cognitive systems that allow them to recover an accurate "causal map" of the world: an abstract, coherent, learned representation of the causal relations among events. This kind of knowledge can be perspicuously understood in terms of the formalism of directed graphical causal models, or Bayes nets. Children's causal learning and inference may involve computations similar to those for learning causal Bayes nets and for predicting with them. Experimental results suggest that 2- to 4-year-old children construct new causal maps and that their learning is consistent with the Bayes net formalism.