Physiological input enables hands-free, embodied interaction in games, but its inherent signal variability complicates precise control. Most systems suppress this variability to achieve stability, leaving fine-grained variability of user effort underutilized. In this paper, we propose a dual-stream architecture that uses physiological signals for action control and residual effort-coupled variability as perceptual feedback to shape game feel. We investigate this approach using tongue-based input sensed via non-invasive surface electromyography (sEMG) in two studies. In Study 1 (n = 24), we evaluated the feasibility of tongue pressure in primary and modifier roles. Integrating head-gaze for selection with tongue pressure for confirmation significantly outperformed tongue-only input on performance measures, suggesting that separating spatial intent from physical effort can yield more stable control. In Study 2 (n = 12), we examined the experiential impact of residual variability in tongue pressure control as feedback. Rendering this residual jitter as a perceptual response led participants to misattribute their own effort to external resistance or animacy, a phenomenon we describe as physiological ventriloquism\rev, where one’s effort feels externally owned. We contribute a design perspective that reframes physiological variability not as error to be eliminated, but as expressive material when architecturally separated from control.
