Simon says: Reliability and the role of working memory and attentional control in the Simon task

TheSimon effect refers to the observation that subjects identify targets (e.g., colors) faster when the irrelevant spatial location of the target corresponds to the location of the response key. Theoretical accounts of the Simon effect typically explain performance in terms of automatic and controlled processes. Furthermore, the relative contributions of automatic and controlled processes are held to change as a function of the proportion of compatible to incompatible trials (compatibility proportion). Data are presented demonstrating that the reliability of the Simon effect, indexed by correlating its magnitude within subjects across blocks of trials, varied substantially as a function of the compatibility proportion. When the compatibility proportion was high, so was reliability. When the compatibility proportion was low, reliability was low as well. The results are discussed in terms of the relative reliability of automatic and controlled processes and the role of working memory and attentional control in goal maintenance.     

Predictive coding: an account of the mirror neuron system

Is it possible to understand the intentions of other people by simply observing their actions? Many believe that this ability is made possible by the brain’s mirror neuron system through its direct link between action and observation. However, precisely how intentions can be inferred through action observation has provoked much debate. Here we suggest that the function of the mirror system can be understood within a predictive coding framework that appeals to the statistical approach known as empirical Bayes. Within this scheme the most likely cause of an observed action can be inferred by minimizing the prediction error at all levels of the cortical hierarchy that are engaged during action observation. This account identifies a precise role for the mirror system in our ability to infer intentions from actions and provides the outline of the underlying computational mechanisms.     

The effects of ordinal load on incidental temporal learning

How can we grasp the temporal structure of events? A few studies have indicated that representations of temporal structure are acquired when there is an intention to learn, but not when learning is incidental. Response-to-stimulus intervals, uncorrelated temporal structures, unpredictable ordinal information, and lack of metrical organization have been pointed out as key obstacles to incidental temporal learning, but the literature includes piecemeal demonstrations of learning under all these circumstances. We suggest that the unacknowledged effects of ordinal load may help reconcile these conflicting findings, ordinal load referring to the cost of identifying the sequence of events (e.g., tones, locations) where a temporal pattern is embedded. In a first experiment, we manipulated ordinal load into simple and complex levels. Participants learned ordinal-simple sequences, despite their uncorrelated temporal structure and lack of metrical organization. They did not learn ordinal-complex sequences, even though there were no response-to-stimulus intervals nor unpredictable ordinal information. In a second experiment, we probed learning of ordinal-complex sequences with strong metrical organization, and again there was no learning. We conclude that ordinal load is a key obstacle to incidental temporal learning. Further analyses showed that the effect of ordinal load is to mask the expression of temporal knowledge, rather than to prevent learning.     

Perception of the length of an object through dynamic touch is invariant across changes in the medium

Rotational inertia—a mechanical quantity that describes the differential resistance of an object to angular acceleration in different directions—has been shown to support perception of the properties of that object through dynamic touch (wielding). The goal of the present study was to examine if perception of the length of an object through dynamic touch depends on its rotational inertia, independent of the medium in which it is wielded. The participants (n = 14) wielded 12 different objects held in air or completely immersed in water and reported perceived lengths of those objects. Each object consisted of a rod of a particular density with a particular number of stacked steel rings attached at a particular location along its length. Perceived length was invariant across medium. In addition, a single-valued function of the major eigenvalue, I ₁, and the minor eigenvalue, I ₃, of the rotational inertia, I, of the 12 objects predicted the perceived lengths of those objects in both air and water, and the perceived lengths were invariant across the two media. These results support the hypothesis that the informational support for perception of the length of an object through dynamic touch is invariant across changes in the medium.     

The P600 in Implicit Artificial Grammar Learning

The suitability of the artificial grammar learning (AGL) paradigm to capture relevant aspects of the acquisition of linguistic structures has been empirically tested in a number of EEG studies. Some have shown a syntax‐related P600 component, but it has not been ruled out that the AGL P600 effect is a response to surface features (e.g., subsequence familiarity) rather than the underlying syntax structure. Therefore, in this study, we controlled for the surface characteristics of the test sequences (associative chunk strength) and recorded the EEG before (baseline preference classification) and after (preference and grammaticality classification) exposure to a grammar. After exposure, a typical, centroparietal P600 effect was elicited by grammatical violations and not by unfamiliar subsequences, suggesting that the AGL P600 effect signals a response to structural irregularities. Moreover, preference and grammaticality classification showed a qualitatively similar ERP profile, strengthening the idea that the implicit structural mere‐exposure paradigm in combination with preference classification is a suitable alternative to the traditional grammaticality classification test.     

Everybody Will Win,and All Must Be Hired: Comparing Additivity Neglect with the Nonselective Superiority Bias

Two streams of research looking at referent‐dependent judgments from slightly different angles are subadditivity research and research on the nonselective superiority bias. Both biases violate basic formal constraints: the probabilities of a set of exclusive events cannot add up to more than 100%, and a set of attractive candidates cannot all be rated as superior to the group mean. We examine in three experiments how these two biases are related, by asking the same participants to perform both kinds of tasks on the same material. Both biases appear to be widespread, even for sets where all alternatives are presented together, but they differ in the way they are affected by response format and experimental setup. Thus, presenting participants with an unbiased set of ratings will reduce but not normalize their probability estimates of the same alternatives; while presenting them with an unbiased (additive) set of probabilities will make most alternatives appear inferior to the group mean, inverting the superiority bias. Self‐reports reveal that additivity neglect and the nonselective superiority bias can be based on two main response‐strategies: (i) considering each alternative independently or (ii) comparing alternatives, while neglecting their complementarity. In both cases, assessments will be the outcome of a compromise between the perceived “absolute” merits of each alternative, its standing relative to referents, and properties of the response scale. Copyright © 2015 John Wiley & Sons, Ltd.     

Stone-Tool Use in Wild Monkeys: Implications for the Study of the Body-Plus-Tool System

Handheld tools transform the actor's body into a body-plus-tool system such that the fit of the actor's body, the tool, and the task demand channel movement in action. In this study, we performed a biomechanical analysis of percussive actions in wild bearded capuchin monkeys, Sapajus libidinosus at Fazenda Boa Vista, Brazil, as they cracked open tucum nuts with anvil-and-hammer tools from the frame of reference of the body-plus-tool system. The ratio of hammer mass to body mass—the “body-scaled hammer mass”—influenced the monkeys' actions with a hammer and their performance in cracking nuts. Both body mass and hammer mass did not independently influence the monkeys' actions with a hammer and their performance in cracking nuts. These findings support the hypothesis that the properties of the body-plus-tool system are not simply the sum of the properties of the body and the tool.     

Happiness and health behaviours among university students from 24 low,middle and high income countries

The aim of this study was to examine health behaviours and happiness and associated factors in low, middle and high income countries. In a cross-sectional survey, 17 508 undergraduate university students (mean age 20.9, SD = 2. 8) from 25 universities in 24 countries across Asia, Africa and the Americas self-completed anonymous questionnaires. Results indicate that the overall happiness mean score among university students across 24 countries was 13.7 (range 4–20). Generally, the study found that university students from countries of the Caribbean, South America and sub-Saharan Africa had greater happiness scores than students from countries in North Africa and Asia. In multivariate linear regression analysis, better subjective socio-economic status, coming from an higher income country, higher social support, higher intrinsic religiosity, higher personal mastery, positive health behaviours (regular breakfast, adequate physical activity, habitual seatbelt use, regular dental check-ups, not having had an injury, not drinking and driving) and negative health behaviours (not having three or more servings of vegetables and eating red meat daily) were correlated with happiness. Improvement to the happiness of university students should consider regional differences in socio-economic environment.     

Lifestyle and mental health among school-going adolescents in Namibia

This study examined the association between lifestyle behaviours and psychological distress indicators among school-going adolescents. The analysis included 4 531 school children, 11–18 years of age, who completed the Namibia Global School-based Student Health Survey (GSHS) in 2013. Multivariable logistic regression analysis found that engaging in a greater number of harmful consumptive, sedentary and sexual risk behaviours carried an elevated risk for anxiety, suicide attempt and loneliness. Adolescents with co-occurring health risk behaviours have poorer mental health outcomes with socio-economic vulnerability.