Humans sacrifice decision-making for action execution when a demanding control of movement is required

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>A growing body of evidence suggests that decision-making and action execution are governed by partly overlapping operating principles. Especially, previous work proposed that a shared decision urgency/movement vigor signal, possibly computed in the basal ganglia, coordinates both deliberation and movement durations in a way that maximizes the reward rate. Recent data support one aspect of this hypothesis, indicating that the urgency level at which a decision is made influences the vigor of the movement produced to express this choice. Here we investigated whether conversely, the motor context in which a movement is executed determines decision speed and accuracy. Twenty human subjects performed a probabilistic decision task in which perceptual choices were expressed by reaching movements toward targets whose size and distance from a starting position varied in distinct blocks of trials. We found strong evidence for an influence of the motor context on most of the subjects’ decision policy but contrary to the predictions of the “shared regulation” hypothesis, we observed that slow movements executed in the most demanding motor blocks in terms of accuracy were often preceded by faster and less accurate decisions compared to blocks of trials in which big targets allowed expression of choices with fast and inaccurate movements. These results suggest that decision-making and motor control are not regulated by one unique “invigoration” signal determining both decision urgency and action vigor, but more likely by independent, yet interacting, decision urgency and movement vigor signals.</jats:p><jats:sec><jats:title>NEW &amp; NOTEWORTHY</jats:title><jats:p>Recent hypotheses propose that choices and movements share optimization principles derived from economy, possibly implemented by one unique context-dependent regulation signal determining both processes speed. In the present behavioral study conducted on human subjects, we demonstrate that action properties indeed influence perceptual decision-making, but that decision duration and action vigor are actually independently set depending on the difficulty of the movement executed to report a choice.</jats:p></jats:sec>

Age-related deficits in rapid visuomotor decision-making

“…3A). This resulted in more initial and final decision errors during interception, supporting recent evidence that decision-making is impaired when the movement required is more demanding to perform (Hesse et al, 2020; Reynaud et al, 2020). The dorsal and ventral streams are driven predominantly by magnocellular and parvocellular inputs, respectively, and axons of parvocellular cells have slower conduction velocity than magnocellular cells (Maunsell et al, 1999).…”

Dissociating the impact of movement time and energy costs on decision-making and action initiation in humans

“…We performed an a priori power analysis to estimate the optimal combination of trials per condition and participant numbers, depending on expected effect sizes and variabilities (Baker et al 2020). Based on a previous experiment conducted on 20 human subjects performing a similar task (Reynaud et al 2020), we estimated a mean difference of decision duration between motor conditions of 150ms, a within-subject standard deviation (SD) of 420ms, a between-subject SD of 230ms, and we set the alpha level to 0.05. For a standard power of 80%, 22 subjects had to be tested on 32 trials per condition.…”

“…To increase the power and reach 90%, we needed to test at least 28 subjects in about 80 trials per conditions. Given our past experience with similar experiments (Reynaud et al 2020; Thura 2020), executing a minimum of 80 trials per condition in an experiment that is designed to include 3 conditions takes about one hour, which is an acceptable duration for a healthy, young subject. But to increase the statistical power of our results further without increasing session duration, we tested each participant twice, in two separate sessions.…”

“…Importantly, the size of the movement target was chosen to be large enough to minimize the motor accuracy constraints and avoid major speed-accuracy tradeoff adjustments. The effect of motor accuracy on decision-making has been investigated in a recent publication (Reynaud et al 2020).…”

“…Together, these studies suggest that movement vigor is coordinated with decision-making urgency to optimize the rate of reward. Recently, we provided strong support for this hypothesis by showing that when movement accuracy requirements are relaxed, decision duration is extended, allowing human subjects to increase their choice accuracy (Reynaud et al 2020). The present work is designed to investigate this coordination between decision and action further and assess whether, how and why motor time and/or energy costs influence perceptual choices in human subjects.…”