Problem solving by worker bumblebees Bombus impatiens (Hymenoptera: Apoidea)

During foraging, worker bumblebees are challenged by simple to complex tasks. Our goal was to determine whether bumblebees could successfully accomplish tasks that are more complex than those they would naturally encounter. Once the initial training to successfully manipulate a simple, artificial flower was completed, the bees were either challenged with a series of increasingly difficult tasks or with the most difficult task without the opportunity for prior learning. The first experiment demonstrated that the bees learned to slide or lift caps that prevented their access to the reinforcer sugar solution through a series of tasks with increasing complexity: moving one cap either to the right or to the left, or lifting it up. The second experiment demonstrated that the bees learned to push balls of escalating masses (diameters 1 and 1.27 cm) from the access to the hidden rewarding (sugar syrup) reservoir of artificial flowers. In both experiments, when bees with experience with only the simplest task (i.e. an artificial flower without a barrier to the reinforcer) were presented next with the most complex or difficult task, they failed. Only by proceeding through the series of increasingly difficult tasks were they able to succeed at the most difficult. We also noted idiosyncratic behaviours by individual bees in learning to succeed. Our results can be interpreted within the context of Skinnerian shaping and possibly scaffold learning.     

Testing the difficulty theory of the SON‐R –17, a non‐verbal test of intelligence

Fischer's (1973) linear logistic test model can be used to test hypotheses regarding the effect of covariates on item difficulty and to predict the difficulty of newly constructed test items. However, its assumptions of equal discriminatory power across items and a perfect prediction of item difficulty are never absolutely met. The amount of misfit in an application of a Bayesian version of the model to two subtests of the SON‐R –17 is investigated by means of item fit statistics in the framework of posterior predictive checks and by means of a comparison with a model that allows for residual (co)variance in the item parameters. The effect of the degree of residual (co)variance on the robustness of inferences is investigated in a simulation study.     

Reliance,Trust, and Belief

Abstract

An adequate theory of the nature of belief should help us explain the most obvious features of belief as we find it. Among these features are: guiding action and reasoning non-inferentially; varying in strength in ways that are spontaneously experience-sensitive; ‘aiming at truth’ in some sense and being evaluable in terms of correctness and warrant; possessing inertia across time and constancy across contexts; sustaining expectations in a manner mediated by propositional content; shaping the formation and execution of plans; generalizing spontaneously projectively; and being independent of the will and resisting instrumentalization. Using the method of ‘creature construction’, I attempt to show how we can build an attitude with these features step-by-step from simpler components, thereby avoiding the problems of regress or circularity affecting a number of influential accounts of belief.     

The effect of psychological stress and expectation on auditory perception: A signal detection analysis

Both psychological stress and predictive signals relating to expected sensory input are believed to influence perception, an influence which, when disrupted, may contribute to the generation of auditory hallucinations. The effect of stress and semantic expectation on auditory perception was therefore examined in healthy participants using an auditory signal detection task requiring the detection of speech from within white noise. Trait anxiety was found to predict the extent to which stress influenced response bias, resulting in more anxious participants adopting a more liberal criterion, and therefore experiencing more false positives, when under stress. While semantic expectation was found to increase sensitivity, its presence also generated a shift in response bias towards reporting a signal, suggesting that the erroneous perception of speech became more likely. These findings provide a potential cognitive mechanism that may explain the impact of stress on hallucination‐proneness, by suggesting that stress has the tendency to alter response bias in highly anxious individuals. These results also provide support for the idea that top‐down processes such as those relating to semantic expectation may contribute to the generation of auditory hallucinations.     

School System Evaluation by Value Added Analysis Under Endogeneity

Value added is a common tool in educational research on effectiveness. It is often modeled as a (prediction of a) random effect in a specific hierarchical linear model. This paper shows that this modeling strategy is not valid when endogeneity is present. Endogeneity stems, for instance, from a correlation between the random effect in the hierarchical model and some of its covariates. This paper shows that this phenomenon is far from exceptional and can even be a generic problem when the covariates contain the prior score attainments, a typical situation in value added modeling. Starting from a general, model-free definition of value added, the paper derives an explicit expression of the value added in an endogeneous hierarchical linear Gaussian model. Inference on value added is proposed using an instrumental variable approach. The impact of endogeneity on the value added and the estimated value added is calculated accurately. This is also illustrated on a large data set of individual scores of about 200,000 students in Chile.