Quantifying the Sense Agency: A Forced Choice Paradigm for Assessing Intentional Binding During Upper Limb Movements.

The sense of agency is the perceptual experience of authoring our volitional actions. It is a valuable framework for assessing perceptions of control and the quality of interaction for users operating assistive devices. Intentional binding (IB) is a quantitative measure of the sense of agency where individuals perceive temporal compression between a volitional action and its sensory outcome. IB has been investigated during simple button press actions, but little work extends findings to gross whole-limb movements that are more relevant to assistive or rehabilitative robotics. This study develops and examines the feasibility of a novel, high-resolution approach for assessing IB using a forced two-choice discrimination paradigm. We designed a target acquisition task that required movement of the whole upper limb. Eight participants discriminated time durations between pairs of auditory tones coinciding with paired active and passive movements executed on a Kinarm. Participants reported which movement had a shorter time interval between tones while we varied time delays across movements and trials. We fit psychometric curves to participant responses and achieve a high-resolution estimate of IB biases while also providing a new slope dimension of analysis for IB experiences. The median bias across participants was -36.2ms (IQR: 145.1). We measured IB biases in whole limb movements with high resolution using this method and share its implications for assistive device design.