HD Online Player (comprehensive.meta.analysis.2.2.064.)
Abdul Soumphonphakdy
The current study may shed light on one of the behavioral mechanisms underlying IGD, namely the discounting of probabilistic gains and losses45. Despite previous inconsistent findings about the differences in the rate of PD between subjects with IGD and normal controls, our study showed that the former had a lower PD rate than that in the latter with a moderate effect size, suggesting that subjects with IGD tended to underestimate the consequences of risky behaviors compared to the tendency in healthy controls. Previous studies found that PD rate is associated with risk taking and gamblers who had elevated risk propensity also had lower PD rates than those in controls16,46. Therefore, it is possible that the IGD group had impaired prospective thinking which involved risk evaluation to render them vulnerable to easy addiction to online games without considering the potential negative consequences. The finding is supported by that of previous studies investigating the underlying neural mechanism among individuals with IGD, which demonstrated impaired functional connectivity in brain regions involving the reward circuits24, less engagement in the executive control network29 and less neural response in certain brain regions related to addictive behaviors such as parahippocampal gyrus, the anterior cingulate cortex, and the medial frontal gyrus39 compared to those in normal subjects.
Doi & Barendregt working in collaboration with Khan, Thalib and Williams (from the University of Queensland, University of Southern Queensland and Kuwait University), have created an inverse variance quasi likelihood based alternative (IVhet) to the random effects (RE) model for which details are available online.[59] This was incorporated into MetaXL version 2.0,[65] a free Microsoft Excel add-in for meta-analysis produced by Epigear International Pty Ltd, and made available on 5 April 2014. The authors state that a clear advantage of this model is that it resolves the two main problems of the random effects model. The first advantage of the IVhet model is that coverage remains at the nominal (usually 95%) level for the confidence interval unlike the random effects model which drops in coverage with increasing heterogeneity.[50][51] The second advantage is that the IVhet model maintains the inverse variance weights of individual studies, unlike the RE model which gives small studies more weight (and therefore larger studies less) with increasing heterogeneity. When heterogeneity becomes large, the individual study weights under the RE model become equal and thus the RE model returns an arithmetic mean rather than a weighted average. This side-effect of the RE model does not occur with the IVhet model which thus differs from the RE model estimate in two perspectives:[59] Pooled estimates will favor larger trials (as opposed to penalizing larger trials in the RE model) and will have a confidence interval that remains within the nominal coverage under uncertainty (heterogeneity). Doi & Barendregt suggest that while the RE model provides an alternative method of pooling the study data, their simulation results[66] demonstrate that using a more specified probability model with untenable assumptions, as with the RE model, does not necessarily provide better results. The latter study also reports that the IVhet model resolves the problems related to underestimation of the statistical error, poor coverage of the confidence interval and increased MSE seen with the random effects model and the authors conclude that researchers should henceforth abandon use of the random effects model in meta-analysis. While their data is compelling, the ramifications (in terms of the magnitude of spuriously positive results within the Cochrane database) are huge and thus accepting this conclusion requires careful independent confirmation. The availability of a free software (MetaXL)[65] that runs the IVhet model (and all other models for comparison) facilitates this for the research community.
HD Online Player (comprehensive.meta.analysis.2.2.064.)
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