Abstract
<p>The sense of agency, the experience of controlling one’s actions and their outcomes, is essential to motor control, social cognition, and the design of assistive devices. Intentional binding (IB), the subjective compression in time between a voluntary action and its sensory outcome, is often used as a quantitative measure of agency. However, current IB methods are cognitively demanding, and recent studies suggest that temporal compression may reflect causal expectations rather than intention itself. To address this, we conducted a psychophysical two-alternative forced-choice study that isolated intention from causation by matching causal outcomes across conditions. Participants performed pairs of movements on a Kinarm device and judged which of two intervals between a visual cue at the end of movement and a post-movement tone was shorter. Pairs consisted of either active and passive movements (experimental group, n = 19) or two passive movements (control group, n = 19). We observed no group differences in time compression bias, defined as the point of subjective equality. In contrast, the experimental group showed significantly lower just-noticeable difference values than the control group (p &lt; 0.01), reflecting a lower temporal difference limen (TDL). This finding suggests that the TDL may capture a link between intention and action and may serve as an implicit measure of the sense of agency. These results support recent claims that intentional binding may primarily reflect causal binding and provide evidence for TDL as a measure for evaluating the sense of agency.</p>