title: Using Covert Response Activation to Test Latent Assumptions of Formal Decision-Making Models in Humans.
abstract: Most decisions that we make build upon multiple streams of sensory evidence and control mechanisms are needed to filter out irrelevant information. Sequential sampling models of perceptual decision making have recently been enriched by attentional mechanisms that weight sensory evidence in a dynamic and goal-directed way. However, the framework retains the longstanding hypothesis that motor activity is engaged only once a decision threshold is reached. To probe latent assumptions of these models, neurophysiological indices are needed. Therefore, we collected behavioral and EMG data in the flanker task, a standard paradigm to investigate decisions about relevance. Although the models captured response time distributions and accuracy data, EMG analyses of response agonist muscles challenged the assumption of independence between decision and motor processes. Those analyses revealed covert incorrect EMG activity ("partial error") in a fraction of trials in which the correct response was finally given, providing intermediate states of evidence accumulation and response activation at the single-trial level. We extended the models by allowing motor activity to occur before a commitment to a choice and demonstrated that the proposed framework captured the rate, latency, and EMG surface of partial errors, along with the speed of the correction process. In return, EMG data provided strong constraints to discriminate between competing models that made similar behavioral predictions. Our study opens new theoretical and methodological avenues for understanding the links among decision making, cognitive control, and motor execution in humans.
  
  
  CONCLUSIONS
  Sequential sampling models of perceptual decision making assume that sensory information is accumulated until a criterion quantity of evidence is obtained, from where the decision terminates in a choice and motor activity is engaged. The very existence of covert incorrect EMG activity ("partial error") during the evidence accumulation process challenges this longstanding assumption. In the present work, we use partial errors to better constrain sequential sampling models at the single-trial level.
authors.affiliation: Laboratoire de Neurosciences Cognitives, Fédération de Recherche 3C, Case C, Aix-Marseille Université, Centre National de la Recherche Scientifique, 13331 Marseille cedex 3, France, Institut de Neurosciences de la Timone, Aix-Marseille Université, Centre National de la Recherche Scientifique, Faculté de Médecine, 13005 Marseille, France, and.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Servant
authors.affiliation: Brain and Behavior Laboratory, Department of Psychology, Syracuse University, Syracuse, New York 13244.
authors.forename: Corey
authors.initials: C
authors.lastname: White
authors.affiliation: Institut de Neurosciences de la Timone, Aix-Marseille Université, Centre National de la Recherche Scientifique, Faculté de Médecine, 13005 Marseille, France, and.
authors.forename: Anna
authors.initials: A
authors.lastname: Montagnini
authors.affiliation: Laboratoire de Neurosciences Cognitives, Fédération de Recherche 3C, Case C, Aix-Marseille Université, Centre National de la Recherche Scientifique, 13331 Marseille cedex 3, France, boris.burle@univ-amu.fr.
authors.forename: Borís
authors.initials: B
authors.lastname: Burle
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D003198:Computer Simulation; D003657:Decision Making / Q000502:physiology*; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008959:Models, Neurological; D010775:Photic Stimulation; D011237:Predictive Value of Tests; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time; D055815:Young Adult
keywords: accumulation models; decision making; electromyography; electrophysiology; partial errors