Variability in the analysis of a single neuroimaging dataset by many teams.

Data analysis workflows in many scientific domains have become increasingly complex and flexible. Here we assess the effect of this flexibility on the results of functional magnetic resonance imaging by asking 70 independent teams to analyse the same dataset, testing the same 9 ex-ante hypotheses1. The flexibility of analytical approaches is exemplified by the fact that no two teams chose identical workflows to analyse the data. This flexibility resulted in sizeable variation in the results of hypothesis tests, even for teams whose statistical maps were highly correlated at intermediate stages of the analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Notably, a meta-analytical approach that aggregated information across teams yielded a significant consensus in activated regions. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset2-5. Our findings show that analytical flexibility can have substantial effects on scientific conclusions, and identify factors that may be related to variability in the analysis of functional magnetic resonance imaging. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for performing and reporting multiple analyses of the same data. Potential approaches that could be used to mitigate issues related to analytical variability are discussed.

Robust priors for regularized regression.

Induction benefits from useful priors. Penalized regression approaches, like ridge regression, shrink weights toward zero but zero association is usually not a sensible prior. Inspired by simple and robust decision heuristics humans use, we constructed non-zero priors for penalized regression models that provide robust and interpretable solutions across several tasks. Our approach enables estimates from a constrained model to serve as a prior for a more general model, yielding a principled way to interpolate between models of differing complexity. We successfully applied this approach to a number of decision and classification problems, as well as analyzing simulated brain imaging data. Models with robust priors had excellent worst-case performance. Solutions followed from the form of the heuristic that was used to derive the prior. These new algorithms can serve applications in data analysis and machine learning, as well as help in understanding how people transition from novice to expert performance.

Social Information Is Integrated into Value and Confidence Judgments According to Its Reliability.

How much we like something, whether it be a bottle of wine or a new film, is affected by the opinions of others. However, the social information that we receive can be contradictory and vary in its reliability. Here, we tested whether the brain incorporates these statistics when judging value and confidence. Participants provided value judgments about consumer goods in the presence of online reviews. We found that participants updated their initial value and confidence judgments in a Bayesian fashion, taking into account both the uncertainty of their initial beliefs and the reliability of the social information. Activity in dorsomedial prefrontal cortex tracked the degree of belief update. Analogous to how lower-level perceptual information is integrated, we found that the human brain integrates social information according to its reliability when judging value and confidence.SIGNIFICANCE STATEMENT The field of perceptual decision making has shown that the sensory system integrates different sources of information according to their respective reliability, as predicted by a Bayesian inference scheme. In this work, we hypothesized that a similar coding scheme is implemented by the human brain to process social signals and guide complex, value-based decisions. We provide experimental evidence that the human prefrontal cortex's activity is consistent with a Bayesian computation that integrates social information that differs in reliability and that this integration affects the neural representation of value and confidence.

Subjective value and decision entropy are jointly encoded by aligned gradients across the human brain.

Recent work has considered the relationship between value and confidence in both behavioural and neural representation. Here we evaluated whether the brain organises value and confidence signals in a systematic fashion that reflects the overall desirability of options. If so, regions that respond to either increases or decreases in both value and confidence should be widespread. We strongly confirmed these predictions through a model-based fMRI analysis of a mixed gambles task that assessed subjective value (SV) and inverse decision entropy (iDE), which is related to confidence. Purported value areas more strongly signalled iDE than SV, underscoring how intertwined value and confidence are. A gradient tied to the desirability of actions transitioned from positive SV and iDE in ventromedial prefrontal cortex to negative SV and iDE in dorsal medial prefrontal cortex. This alignment of SV and iDE signals could support retrospective evaluation to guide learning and subsequent decisions.

Fast or frugal, but not both: Decision heuristics under time pressure.

Heuristics are simple, yet effective, strategies that people use to make decisions. Because heuristics do not require all available information, they are thought to be easy to implement and to not tax limited cognitive resources, which has led heuristics to be characterized as fast-and-frugal. We question this monolithic conception of heuristics by contrasting the cognitive demands of two popular heuristics, Tallying and Take-the-Best. We contend that heuristics that are frugal in terms of information usage may not always be fast because of the attentional control required to implement this focus in certain contexts. In support of this hypothesis, we find that Take-the-Best, while being more frugal in terms of information usage, is slower to implement and fares worse under time pressure manipulations than Tallying. This effect is then reversed when search costs for Take-the-Best are reduced by changing the format of the stimuli. These findings suggest that heuristics are heterogeneous and should be unpacked according to their cognitive demands to determine the circumstances a heuristic best applies. (PsycINFO Database Record

The intrinsic value of choice: The propensity to under-delegate in the face of potential gains and losses.

Human beings are often faced with a pervasive problem: whether to make their own decision or to delegate the decision task to someone else. Here, we test whether people are inclined to forgo monetary rewards in order to retain agency when faced with choices that could lead to losses and gains. In a simple choice task, we show that participants choose to pay in order to control their own payoff more than they should if they were to maximize monetary rewards and minimize monetary losses. This tendency cannot be explained by participants' overconfidence in their own ability, as their perceived ability was elicited and accounted for. Nor can the results be explained by lack of information. Rather, the results seem to reflect an intrinsic value for choice, which emerges in the domain of both gains and of losses. Moreover, our data indicate that participants are aware that they are making suboptimal choices in the normative sense, but do so anyway, presumably for psychological gains.

[Perceived and imagined body image distortion: a possible factor for obesity and overweight in Mexicans]. / Distorsión de imagen corporal percibida e imaginada. Un posible factor para la obesidad y el sobrepeso en mexicanos.

BACKGROUND: Obesity, as an effect of the nutritional transition in developing countries, has become one of México's greatest public health problems. Body image distortion is one of the possible causes of this socially generalized issue. The aim of this study was to obtain three indicators (the representation of the imagined body, the perceived image of the body, and the body mass index -BMI-) to compare them and know the differences between the real image (BMI) and the other two images. METHODS: Inaccuracy of body size estimation was measured through a survey with a ranked scale to determine if the sample (n = 579) had body image distortion, what degree of distortion had, and how body image distortion behaved across age groups from 15 to 69 years old. RESULTS: The age group from 15 to 19 years old was found to be significantly different from all other age groups through a Kruskal-Wallis test. Differences between men and women were found through a Mann-Whitney test. A relation was found between types of body image distortion and the degree of distortion with a multinomial logistic regression model. CONCLUSIONS: Cultural factors could help to explain these findings. If the inaccuracy of body size estimation can be associated to obese and overweight Mexicans in the future, these results will be critical for the analysis of such an epidemic.

Introducción: la obesidad es un efecto de la transición nutricional en varios países y es uno de los problemas de salud pública más graves en México. La distorsión de la imagen corporal es un posible factor importante en este asunto socialmente generalizado. El objetivo fue obtener tres indicadores (la representación del cuerpo imaginado, la imagen percibida del cuerpo y el índice de masa corporal ­IMC­) para compararlos y conocer las diferencias entre la imagen real (IMC) con respecto a las otras dos imágenes. Métodos: la imprecisión al estimar el tamaño corporal se midió por medio de una encuesta con una escala graduada para determinar si la muestra (n = 579) tenía distorsión de la imagen corporal, qué grado de distorsión tenía y cómo se comportaba esta en los diferentes grupos de edad (15-69 años). Resultados: el grupo de edad de 15 a 19 años difirió significativamente de los demás grupos etarios, lo cual quedó demostrado al emplear una prueba Kruskal-Wallis. Las diferencias entre hombres y mujeres fueron encontradas a través de una prueba Mann-Whitney. Asimismo, se encontró una relación entre tipos de distorsión de imagen corporal y grado de distorsión observada por medio de un modelo de regresión logística multinomial. Conclusión: los factores culturales podrían esclarecer estos hallazgos. Si la imprecisión de la estimación del tamaño corporal puede ser asociada al sobrepeso y la obesidad en el futuro, estos resultados serán relevantes para su consecuente análisis.