Underpowered samples,false negatives,and unconscious learning

The scientific community has witnessed growing concern about the high rate of false positives and unreliable results within the psychological literature, but the harmful impact of false negatives has been largely ignored. False negatives are particularly concerning in research areas where demonstrating the absence of an effect is crucial, such as studies of unconscious or implicit processing. Research on implicit processes seeks evidence of above-chance performance on some implicit behavioral measure at the same time as chance-level performance (that is, a null result) on an explicit measure of awareness. A systematic review of 73 studies of contextual cuing, a popular implicit learning paradigm, involving 181 statistical analyses of awareness tests, reveals how underpowered studies can lead to failure to reject a false null hypothesis. Among the studies that reported sufficient information, the meta-analytic effect size across awareness tests was d _z = 0.31 (95 % CI 0.24–0.37), showing that participants’ learning in these experiments was conscious. The unusually large number of positive results in this literature cannot be explained by selective publication. Instead, our analyses demonstrate that these tests are typically insensitive and underpowered to detect medium to small, but true, effects in awareness tests. These findings challenge a widespread and theoretically important claim about the extent of unconscious human cognition.     

Correlating the internal length in strain gradient plasticity theory with the microstructure of material

The internal length is the governing parameter in strain gradient theories which among other things have been used successfully to interpret size effects at the microscale. Physically, the internal length is supposed to be related with the microstructure of the material and evolves during the deformation. Based on Taylor hardening law, we propose a power-law relationship to describe the evolution of the variable internal length with strain. Then, the classical Fleck–Hutchinson strain gradient theory is extended with a strain-dependent internal length, and the generalized Fleck–Hutchinson theory is confirmed here, by comparing our model predictions to recent experimental data on tension and torsion of thin wires with varying diameter and grain size. Our work suggests that the internal length is a configuration-dependent parameter, closely related to dislocation characteristics and grain size, as well as sample geometry when this affects either the underlying microstructure or the ductility of the material.     

Effect of Stress Level on Different Forms of Self-Touch in Pre- and Postadolescent Girls

Self-touch serves for regulation of both hyper- and hypoarousal. It remains unclear if different forms of self-touch occur in different contexts, and if the regulatory mechanisms are learned or innate. The authors describe forms and context of self-touch, and explore age differences in stress processing. They analyzed hand movements of 10 pre- and 10 postadolescent girls in low-stress and high-stress settings and found 3 forms of self-touch. In postadolescent participants, self-touch 2 (irregular structure, rhythmical, medium intensity) and 3 (phasic structure, single accent, medium intensity) were used for self-regulation, whereas self-touch 1 (irregular structure, single accent, low intensity) had conversational reasons. Increasing immobility might represent the inward focus of stressed participants that tried to focus on the task. No differences were found for preadolescent participants. Differences between pre- and postadolescent participants might be due to brain development during adolescence.