Biology subjects

Vadillo, M. A.

Publications and source records attributed to Vadillo, M. A..

3 recordsLinked to original sources

bioRxiv2022

Model-free decision making resists improved instructions and is enhanced by stimulus-response associations

Human behaviour may be thought of as supported by two different computational-learning mechanisms, model-free and model-based respectively. In model-free strategies, stimulus-response associations are strengthened when actions are followed by a reward and weakened otherwise. In model-based learning, previous to selecting an action, the current values of the different possible actions are computed based on a detailed model of the environment. Previous research with the two-stage task suggests that participants behaviour usually shows a mixture of both strategies. But, interestingly, a recent study by da Silva and Hare (2020) found that participants primarily deploy model-based behaviour when they are given detailed instructions about the structure of the task. In the present study, we reproduce this essential experiment. Our results confirm that improved instructions give rise to a stronger model-based component. Crucially, we also found a significant effect of reward that became stronger under conditions that favoured the development of strong stimulus-response associations. This suggests that the effect of reward, often taken as indicator of a model-free component, is related to stimulus-response learning.

neuroscience↗

bioRxiv2022

A call to rethink the cognitive benefits of physical exercise: An umbrella review of randomized controlled trials

Extensive research links regular physical exercise to an overall enhancement of cognitive function across the lifespan. Here, we assess the causal evidence supporting this relationship in the healthy population, using an umbrella review of meta-analyses limited to randomized controlled trials (RCTs). Despite most of the 24 reviewed meta-analyses reporting a positive overall effect, our assessment reveals evidence of low statistical power in the primary RCTs, selective inclusion of studies, publication bias, and large variation in combinations of preprocessing and analytic decisions. In addition, our meta-analysis of all the primary RCTs included in the revised meta-analyses shows small exercise-related benefits (d = 0.22, 95% CI [0.16, 0.28]) that became substantially smaller after accounting for key moderators (i.e., active control and baseline differences; d = 0.13, 95% CI [0.07, 0.20), and negligible after correcting for publication bias (d = 0.05, 95% CrI [-0.09, 0.14]). These findings suggest caution in claims and recommendations linking regular physical exercise to cognitive benefits in the healthy human population until more reliable causal evidence accumulates.

neuroscience↗

bioRxiv2018

Learned predictiveness acquired through experience prevails over the influence of conflicting verbal instructions in rapid selective attention

Previous studies have provided evidence that selective attention tends to prioritize the processing of stimuli that are good predictors of upcoming events over nonpredictive stimuli. In the present study we explored whether the mechanism responsible for this effect critically reflects the influence of prior experience of predictiveness (history of attentional selection of predictive stimuli), or whether it reflects a more flexible process that can be adapted to new verbally acquired knowledge. Our experiment manipulated participants experience of the predictiveness of different stimuli over the course of trial-by-trial training; we then provided explicit verbal instructions regarding stimulus predictiveness that were designed to be either consistent or inconsistent with the previously established learned predictiveness. The effects of training and instruction on attention to stimuli were measured using a dot probe task. Results revealed a rapid attentional bias towards stimuli experienced as predictive (versus those experienced as nonpredictive), that was completely unaffected by verbal instructions. This was not due to participants failure to recall or use instructions appropriately, as revealed by analyses of their learning about stimuli, and their memory for instructions. Overall, these findings suggest that stimuli experienced as predictive through trial-by-trial training produce a relatively inflexible attentional bias based on prior selection history, which is not (always) easily altered through instructions.

animal behavior and cognition↗