Ruby, E. | bioRxiv Science

bioRxiv2017

Finding domain-general metacognitive mechanisms requires using appropriate tasks

An important yet unresolved question is whether or not metacognition consists of domain-general or domain-specific mechanisms. While most studies on this topic suggest a dissociation between metacognitive abilities at the neural level, there are conflicting reports at the behavioral level. Specifically, while McCurdy et al. (2013) found a positive correlation between metacognitive efficiency for visual perception and memory, Baird et al. (2013) didnt find this correlation. One possible explanation for this disparity is that the former included two-alternative-forced choice (2AFC) judgments in both their visual and memory tasks, whereas the latter used 2AFC for one task and yes/no (YN) judgments for the other. In support of this hypothesis, we ran two online experiments meant to mirror McCurdy et al. (2013) and Baird et al. (2013) with considerable statistical power (n=100), and replicated the main findings of both studies. This suggests the finding of McCurdy et al (2013) was not a fluke (i.e. false positive). In a third experiment with the same sample size, which included YN judgments for both tasks, we did not find a correlation between metacognitive functions, suggesting that the conflict between McCurdy et al. (2013) and Baird et al. (2013) stemmed from the use of YN judgments in the latter study. Our results underscore the need to avoid conflating 2AFC and YN judgments, which is a common problem.

neuroscience↗

bioRxiv2017

On a ‘failed’ attempt to manipulate conscious perception with transcranial magnetic stimulation to prefrontal cortex

It has been reported that continuous theta burst transcranial magnetic stimulation (TMS) to the dorsolateral prefrontal cortex (DLPFC) impairs metacognitive awareness in visual perception (Rounis et al., 2010). Bor et al. (2017) recently attempted to replicate this result. However, the authors modified the experimental design of the original study considerably, meaning that this was not strictly a replication. In some cases, the changes are a priori expected to lower the chance of obtaining positive findings. Despite these changes, the researchers in fact still found an effect similar to Rounis et al.s, but they claimed that it was necessary to adopt certain criteria to discard {bsim}30% of their subjects, after which a null result was reported. Using computer simulations, we evaluated whether the subject exclusion criteria Bor et al. adopted was appropriate or beneficial. We found that, contrary to their intended purpose, excluding subjects by their criteria does not actually reduce false positive rates. Taking into account both their positive result (without subject exclusion) and negative result (after exclusion) in a Bayesian framework, we further found that their results suggest a 75% or greater likelihood that TMS to DLPFC does in fact impair metacognition, directly contradicting their claim of replication failure. That lesion and chemical inactivation studies are known to demonstrate positive effects in similar paradigms further suggests that Bor et al.s alleged negative finding cannot be taken as evidence against the role of the prefrontal cortex in conscious perception in general.

neuroscience↗