RuCCS: Dr. Jason Friedman - In-person talk - September 20, 2022

Abstract: Simple two-alternative choices in humans (e.g., are these dots moving left or right) are often modeled using the drift-diffusion model, where evidence is accumulated in a noisy process until a bound is reached. This bound then determines which choice will be made. Often button press (reaction time) responses are used to fit these models, as the button press is assumed to occur at the conclusion of the process (when a bound is reached). In this talk, I will describe an alternative method, where we use arm movements instead of button presses to fit a model, when subjects reach out and touch a target and the arm movements are recorded using a motion capture system. Importantly, we force the subjects to begin moving very early (less than 350 ms), likely before a final decision has been made. The benefit of this technique is that we can then observe through the kinematics of the arm movements the unfolding decision-making process. I will detail how we can decompose continuous movements into a small number of temporally overlapping movement primitives, and how we can use this technique to probe the status of the decision variable before a final decision is made. I will provide examples of how we used this technique to quantify the decision process in a number of different tasks, and how we can use this technique to determine the temporal dynamics of consciously and unconsciously perceived stimuli.
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