The effects of extrinsic reinforcement on intrinsic motivation

In this paper, the role of extrinsic reinforcement in intrinsic motivation is discussed in terms of Deci's cognitive attribution theory. The competing response hypothesis and the frustration hypothesis are presented as alternative modes of analysis. “Undermining” is the phenomenon proposed by the cognitive attribution theorists that accounts for reported decrements in intrinsically motivated behaviors following external rewards. The literature regarding undermining in token economy research is critically evaluated. The author concludes that: (a) Cognitive attribution theory lacks parsimony, in that extant reinforcement analysis can account for undermining with equal facility. (b) Undermining is of little significance as a concept, due to its elusive and transient impact on operant behavior.     

Children born at risk: What's happening in kindergarten?

Many studies examine the development of infants born at risk for medical and developmental problems during the early years of life, but far fewer follow these children into their school years. This project compared high-risk vs. low-risk children in their performance on the WPPSI at pre- and postkindergarten levels. In general, both groups of children demonstrated increases in performance; however, their patterns of performance were different. The high-risk children showed increases predominantly in the Performance areas of the test, whereas the low-risk children demonstrated increases predominantly in the Verbal areas.     

Concordance of apolipoprotein B concentration with the Friedewald,Martin-Hopkins,and Sampson formulas for calculating LDL cholesterol

IntroductionTwo new formulas, the Martin-Hopkins and the Sampson formula, were recently developed to overcome shortcomings of the Friedewald formula for calculating LDL-cholesterol. We aimed to compare the concordance of the two formulas with apolipoprotein B (apoB), a surrogate marker of the number of LDL particles.Materials and methodsIn a study of serum lipid data of 1179 patients who consulted the AZ St-Jan Hospital Bruges for cardiovascular risk assessment, the correlation and concordance of the Friedewald, Martin-Hopkins and Sampson formulas with apoB concentration, measured by immunonephelometry, were determined and compared.ResultsThe Martin-Hopkins formula showed significantly higher correlation coefficient than the Friedewald formula with apoB in the entire dataset and in patients with low LDL-cholesterol < 1.8 mmol/L. Both Martin-Hopkins and Sampson formulas yielded > 70% concordance of LDL-cholesterol with regard to treatment group classification based on population-equivalent thresholds of apoB in hypertriglyceridemic patients (2-4.5 mmol/L), with the highest concordance (75.6%) obtained using Martin-Hopkins formula vs. 60.5% with Friedewald formula.ConclusionThe Martin-Hopkins (and, to a lesser extent, Sampson) formula is more closely associated with the number of LDL particles than Friedewald formula. This, in combination with literature evidence of lesser accuracy of the Friedewald formula, is an argument to switch from Friedewald to a modified, improved formula.