New Estimation Approaches for the Hierarchical Linear Ballistic Accumulator Model

The Linear Ballistic Accumulator (Brown & Heathcote, 2008) model is used as a measurement tool to answer questions about applied psychology. The analyses based on this model depend upon the model selected and its estimated parameters. Modern approaches use hierarchical Bayesian models and Markov chain Monte-Carlo (MCMC) methods to estimate the posterior distribution of the parameters. Although there are several approaches available for model selection, they are all based on the posterior samples produced via MCMC, which means that the model selection inference inherits the properties of the MCMC sampler. To improve on current approaches to LBA inference we propose two methods that are based on recent advances in particle MCMC methodology; they are qualitatively different from existing approaches as well as from each other. The first approach is particle Metropolis-within-Gibbs; the second approach is density tempered sequential Monte Carlo. Both new approaches provide very efficient sampling and can be applied to estimate the marginal likelihood, which provides Bayes factors for model selection. The first approach is usually faster. The second approach provides a direct estimate of the marginal likelihood, uses the first approach in its Markov move step and is very efficient to parallelize on high performance computers. The new methods are illustrated by applying them to simulated and real data, and through pseudo code. The code implementing the methods is freely available.Comment: 35 pages, 6 figures, 7 table

Self-reported mind wandering reflects executive control and selective attention

Mind wandering is ubiquitous in everyday life and has a pervasive and profound impact on task-related performance. A range of psychological processes have been proposed to underlie these performance-related decrements, including failures of executive control, volatile information processing, and shortcomings in selective attention to critical task-relevant stimuli. Despite progress in the development of such theories, existing descriptive analyses have limited capacity to discriminate between the theories. We propose a cognitive-model based analysis that simultaneously explains self-reported mind wandering and task performance. We quantitatively compare six explanations of poor performance in the presence of mind wandering. The competing theories are distinguished by whether there is an impact on executive control and, if so, how executive control acts on information processing, and whether there is an impact on volatility of information processing. Across two experiments using the sustained attention to response task, we fnd quantitative evidence that mind wandering is associated with two latent factors. Our strongest conclusion is that executive control is impaired: increased mind wandering is associated with reduced ability to inhibit habitual response tendencies. Our nuanced conclusion is that executive control defcits manifest in reduced ability to selectively attend to the information value of rare but task-critical events

Effect of protection status on mammal richness and abundance in Afromontane forests of the Udzungwa Mountains, Tanzania

The effectiveness of Protected Areas (PAs) in reducing hunting pressure on mammal populations in tropical forests has rarely been examined at a community-wide level. In African forests, commercial and subsistence hunting are widespread, but assessments of mammal abundance and distribution patterns are often lacking. We investigated patterns of occupancy and abundance for 27 species of medium- to large-bodied mammals (>2 kg) within Tanzania's Udzungwa Mountains Afromontane forests, a global biodiversity hotspot. We sampled 22 forest sites within 10 forests under varying degrees of protection, elevation, distance to extractive communities, and levels of law enforcement. We sampled 251.7 km of recce line transects during dry seasons (July–November) between September 2007 and July 2010. We found a strong positive effect of protection status on species richness and on encounter rates of the most commonly encountered species. Consistent with the levels of resources and enforcement within each PA category, there was a significant progression in species richness and abundance from Forest Reserves through Nature Reserves to sites within Udzungwa Mountains National Park. Protective status closely reflected levels of disturbance. Snaring activity, and distance to ranger posts were identified as significant predictors of overall species richness and encounter rates for mammal species, including endemics. The species-area relationship for our study species was found to be largely overridden by levels of protection. Our findings demonstrate PA effectiveness in Afromontane forests and reinforce concerns over hunting pressures particularly the threat posed by snares

Toward a model-based cognitive neuroscience of mind wandering

Published version also available at http://dx.doi.org/10.1016/j.neuroscience.2015.09.053People often ‘‘mind wander” during everyday tasks, temporarily losing track of time, place, or current task goals. In laboratory-based tasks, mind wandering is often associated with performance decrements in behavioral variables and changes in neural recordings. Such empirical associations provide descriptive accounts of mind wandering – howit affects ongoing task performance – but fail to provide true explanatory accounts – why it affects task performance. In this perspectives paper, we consider mind wandering as a neural state or process that affects the parameters of quantitative cognitive process models, which in turn affect observed behavioral performance. Our approach thus uses cognitive process models to bridge the explanatory divide between neural and behavioral data. We provide an overview of two general frameworks for developing a model-based cognitive neuroscience of mind wandering. The first approach uses neural data to segment observed performance into a discrete mixture of latent task-related and task-unrelated states, and the second regresses single-trial measures of neural activity onto structured trial-by-trial variation in the parameters of cognitive process models. We discuss the relative merits of the two approaches, and the research questions they can answer, and highlight that both approaches allow neural data to provide additional constraint on the parameters of cognitive models, which will lead to a more precise account of the effect of mind wandering on brain and behavior. We conclude by summarizing prospects for mind wandering as conceived within a model-based cognitive neuroscience framework, highlighting the opportunities for its continued study and the benefits that arise from using well-developed quantitative techniques to study abstract theoretical constructs

Testing asteroseismology with Gaia DR2: Hierarchical models of the Red Clump

Asteroseismology provides fundamental stellar parameters independent of distance, but subject to systematics under calibration. Gaia DR2 has provided parallaxes for a billion stars, which are offset by a parallax zero-point. Red Clump (RC) stars have a narrow spread in luminosity, thus functioning as standard candles to calibrate these systematics. This work measures how the magnitude and spread of the RC in the Kepler field are affected by changes to temperature and scaling relations for seismology, and changes to the parallax zero-point for Gaia. We use a sample of 5576 RC stars classified through asteroseismology. We apply hierarchical Bayesian latent variable models, finding the population level properties of the RC with seismology, and use those as priors on Gaia parallaxes to find the parallax zero-point offset. We then find the position of the RC using published values for the zero-point. We find a seismic temperature insensitive spread of the RC of ~0.03 mag in the 2MASS K band and a larger and slightly temperature-dependent spread of ~0.13 mag in the Gaia G band. This intrinsic dispersion in the K band provides a distance precision of ~1% for RC stars. Using Gaia data alone, we find a mean zero-point of -41 $\pm$ 10 $\mu$as. This offset yields RC absolute magnitudes of -1.634 $\pm$ 0.018 in K and 0.546 $\pm$ 0.016 in G. Obtaining these same values through seismology would require a global temperature shift of ~-70 K, which is compatible with known systematics in spectroscopy.Comment: Accepted for publication in MNRA

Chinese mental illness narratives: Controlling the spirit

Through analysis of local level narrative themes and linguistic features and their attendant narrative ‘domains’ and emotive content, this study explicates the discursive forms of Chinese personal narratives about mental illness published in a psychoeducational volume in mainland China. The cultural phenomena underpinning the explicated discursive forms are considered. The study finds that the Chinese mental illness narratives emphasize the problematic nature of the illness experience for the individual concerned, as well as the importance of gaining control over the personal and social disembodiment that mental illness brings about. The language of medicine presents as a dominant linguistic feature of the texts. Narrative authors appear to respond to their illness experience by negotiating and utilizing social relationships and support structures and through active medical intercession. As such, their narratives appear deeply culturally marked despite their psychoeducational intent and institutional context of publication. The study findings bear out the call for more attention to be given to the cultural dimension when analysing illness narratives

Effects of hippocampal damage on reward threshold and response rate during self-stimulation of the ventral tegmental area in the rat

The main purpose of this study was to explore the role of the hippocampus in motivated behavior. Rats with bilateral excitotoxic lesions of the hippocampus and controls were trained to lever press for electrical stimulation of the ventral tegmental area. Rate intensity functions were generated from an ascending and descending series of current intensities. Lesion-induced changes in sensitivity to reward were distinguished from enhancements in motor output by calculating reward thresholds and maximal response rates from the rate-intensity functions. Rats with hippocampal damage showed lower reward thresholds and higher maximal response rates than controls. These results provide further evidence of hippocampal modulation of the nucleus accumbens, suggesting that lesions of this structure enhance sensitivity to reward and increase motor output

The Kepler Smear Campaign: Light curves for 102 Very Bright Stars

We present the first data release of the Kepler Smear Campaign, using collateral 'smear' data obtained in the Kepler four-year mission to reconstruct light curves of 102 stars too bright to have been otherwise targeted. We describe the pipeline developed to extract and calibrate these light curves, and show that we attain photometric precision comparable to stars analyzed by the standard pipeline in the nominal Kepler mission. In this paper, aside from publishing the light curves of these stars, we focus on 66 red giants for which we detect solar-like oscillations, characterizing 33 of these in detail with spectroscopic chemical abundances and asteroseismic masses as benchmark stars. We also classify the whole sample, finding nearly all to be variable, with classical pulsations and binary effects. All source code, light curves, TRES spectra, and asteroseismic and stellar parameters are publicly available as a Kepler legacy sample.Comment: 35 pages, accepted ApJ