title: Motor Cost Influences Perceptual Decisions.
abstract: Perceptual decision making has been widely studied using tasks in which subjects are asked to discriminate a visual stimulus and instructed to report their decision with a movement. In these studies, performance is measured by assessing the accuracy of the participants' choices as a function of the ambiguity of the visual stimulus. Typically, the reporting movement is considered as a mere means of reporting the decision with no influence on the decision-making process. However, recent studies have shown that even subtle differences of biomechanical costs between movements may influence how we select between them. Here we investigated whether this purely motor cost could also influence decisions in a perceptual discrimination task in detriment of accuracy. In other words, are perceptual decisions only dependent on the visual stimulus and entirely orthogonal to motor costs? Here we show the results of a psychophysical experiment in which human subjects were presented with a random dot motion discrimination task and asked to report the perceived motion direction using movements of different biomechanical cost. We found that the pattern of decisions exhibited a significant bias towards the movement of lower cost, even when this bias reduced performance accuracy. This strongly suggests that motor costs influence decision making in visual discrimination tasks for which its contribution is neither instructed nor beneficial.
authors.affiliation: Laboratory of Synthetic Perceptive, Emotive and Cognitive Systems (SPECS), Universitat Pompeu Fabra, Roc Boronat 138, 08018, Barcelona, Spain.
authors.forename: Encarni
authors.initials: E
authors.lastname: Marcos
authors.affiliation: UPMC - Sorbonne Universites, Univ Paris 06, UMR7222, ISIR, 4 Place Jussieu, 75005, Paris, France.|CNRS-UMR 7222, ISIR, 4 Place Jussieu, 75005, Paris, France.
authors.forename: Ignasi
authors.initials: I
authors.lastname: Cos
authors.affiliation: UPMC - Sorbonne Universites, Univ Paris 06, UMR7222, ISIR, 4 Place Jussieu, 75005, Paris, France.|CNRS-UMR 7222, ISIR, 4 Place Jussieu, 75005, Paris, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Girard
authors.affiliation: Laboratory of Synthetic Perceptive, Emotive and Cognitive Systems (SPECS), Universitat Pompeu Fabra, Roc Boronat 138, 08018, Barcelona, Spain.|Institució Catalana de Recercai Estudis Avançats (ICREA), Passeig Lluís Companys 23, 08010, Barcelona, Spain.
authors.forename: Paul F M J
authors.initials: PF
authors.lastname: Verschure
mesh_terms: D000328:Adult; D000465:Algorithms; D002755:Choice Behavior; D003657:Decision Making; D005260:Female; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D009039:Motion Perception; D010465:Perception; D010775:Photic Stimulation; D055815:Young Adult