Back to the basics: Rethinking partial correlation network methodology

The Gaussian graphical model (GGM) is an increasingly popular technique used in psychology to characterize relationships among observed variables. These relationships are represented as elements in the precision matrix. Standardizing the precision matrix and reversing the sign yields corresponding partial correlations that imply pairwise dependencies in which the effects of all other variables have been controlled for. The graphical lasso (glasso) has emerged as the default estimation method, which uses ℓ₁-based regularization. The glasso was developed and optimized for high-dimensional settings where the number of variables (p) exceeds the number of observations (n), which is uncommon in psychological applications. Here we propose to go ‘back to the basics’, wherein the precision matrix is first estimated with non-regularized maximum likelihood and then Fisher Z transformed confidence intervals are used to determine non-zero relationships. We first show the exact correspondence between the confidence level and specificity, which is due to 1 minus specificity denoting the false positive rate (i.e., α). With simulations in low-dimensional settings (p ≪ n), we then demonstrate superior performance compared to the glasso for detecting the non-zero effects. Further, our results indicate that the glasso is inconsistent for the purpose of model selection and does not control the false discovery rate, whereas the proposed method converges on the true model and directly controls error rates. We end by discussing implications for estimating GGMs in psychology.     

Source monitoring in Alzheimer's Disease

Source monitoring is the process of making judgments about the origin of memories. There are three categories of source monitoring: reality monitoring (discrimination between self- versus other-generated sources), external monitoring (discrimination between several external sources), and internal monitoring (discrimination between two types of self-generated sources). We investigated whether Alzheimer's Disease (AD) patients, when compared with young and older adults, are impaired at the same level on the three source monitoring categories. We designed three tasks, one for each source monitoring category. In the first task, aimed at reality monitoring, participants had to remember whether objects were previously placed in a bag by themselves or by the experimenter. In the second task, assessing external monitoring, participants had to remember whether the experimenter had previously placed objects in the bag with a black or white gloved hand. In the third task, measuring internal monitoring, participants had to remember whether they had previously placed or imagined themselves placing objects in the bag. Participants showed worse performances in the external and internal monitoring tasks, when compared with reality monitoring. The external monitoring deficit was even more pronounced in AD patients. Regression analyses showed that variation in the external monitoring performances was reliably predicted by inhibition. Our results emphasize the role of inhibitory processes in AD patients' source monitoring decline. The close relation between source and inhibitory decline in AD is interpreted in terms of a common neural base for both concepts.     

Lifetime and 12‐Month Nonsuicidal Self‐Injury and Academic Performance in College Freshmen

We examined whether nonsuicidal self‐injury (NSSI) is associated with academic performance in college freshmen, using census‐based web surveys (N = 7,527; response = 65.4%). NSSI was assessed with items from the Self‐Injurious Thoughts and Behaviors Interview and subsequently linked with the administratively recorded academic year percentage (AYP). Freshmen with lifetime and 12‐month NSSI showed a reduction in AYP of 3.4% and 5.9%, respectively. The college environment was found to moderate the effect of 12‐month NSSI, with more strongly reduced AYPs in departments with higher‐than‐average mean departmental AYPs. The findings suggest that overall stress and test anxiety are underlying processes between NSSI membership and academic performance.     

Spatio-temporal dynamics of face recognition in a flash: it’s in the eyes

We adapted the Bubbles procedure [Vis. Res. 41 (2001) 2261] to examine the effective use of information during the first 282 ms of face identification. Ten participants each viewed a total of 5100 faces sub‐sampled in space–time. We obtained a clear pattern of effective use of information: the eye on the left side of the image became diagnostic between 47 and 94 ms after the onset of the stimulus; after 94 ms, both eyes were used effectively. This preference for the eyes increased with practice, and was not solely due to the informativeness of the eyes for the task at hand. The bias for the eye on the left side of the image is explained in terms of hemispheric specialization. Although there were individual differences, most participants exhibited this pattern of effective use of information. An intriguing finding is that most participants displayed a clear sinusoidal modulation of effective use of attention through time with a frequency of about 10.6 Hz.     

A Modular Neural Network Model of Concept Acquisition

Previous neural network models of concept learning were mainly implemented with supervised learning schemes. However, studies of human conceptual memory have shown that concepts may be learned without a teacher who provides the category name to associate with exemplars. A modular neural network architecture that realizes concept acquisition through two functionally distinct operations, categorizing and naming, is proposed as an alternative. An unsupervised algorithm realizes the categorizing module by constructing representations of categories compatible with prototype theory. The naming module associates category names to the output of the categorizing module in a supervised mode. In such a modular architecture, the interface between the modules can be conceived of as an “information relay” that encodes, constrains, and propagates important information. Five experiments were conducted to analyze the relationships among internal conceptual codes and simple conceptual and lexical development. The first two experiments show a prototype effect and illustrate some basic characteristics of the system. The third experiment presents a bottom-up model of the narrowing down of children's early lexical categories that honors mutual exclusivity. The fourth experiment introduces top-down constraints on conceptual coding. The fifth experiment exhibits how hierarchical relationships between concepts are learned by the architecture, and also demonstrates how a spectrum of conceptual expertise may gradually emerge as a consequence of experiencing more with certain categories than with others.