Fig. 1: Experimental design and task performance.

a Experimental set up. b Left: Illustration of a virtual environment. Participants steer towards a briefly cued target (yellow disc) using optic flow cues available on the ground plane (visual condition only; platform motion is the only available cue in the inertial condition). During steering, the target becomes less eccentric over time (towards the participant’s midline), while it lowers in the participant’s field of view (color-coded arrow). Right: Overhead view of the spatial distribution of target positions across trials and the corresponding trial trajectories. Red dot shows the starting position of the participant. c Simulated maximum pulse joystick input and the corresponding velocity output under Velocity Control (VC; beige) and Acceleration Control (AC; brown). The input is low-pass filtered to mimic the existence of inertia. The time constant of the filter varies across trials (time constant τ), along with maximum velocity, to ensure comparable travel times across trials. Gray zone: brief cueing period of the target at the beginning of the trial. d Target vs Response. Left: Comparison of the radial distance of a typical subject (stopping location) against the radial distance of the target across all trials. Right: Comparison of the angular eccentricity of the stopping location against the angular eccentricity of the target (both with respect to the starting position) across all trials. Black dashed lines have a unity slope (unbiased performance). Solid lines: linear regression. Data colored according to the sensory condition (red: inertial, cyan: visual). Radial and angular response biases were defined as the slope of the corresponding regressions. e Scatter plot of radial and angular biases in each sensory condition plotted for each individual participant. Ellipses show 68% confidence intervals of the distribution of data points for the corresponding sensory condition. Diamonds (centers of the ellipses) represent the mean radial and angular response biases across participants. Dashed lines indicate unbiased radial or angular position responses. Solid diagonal line has a unit slope. f Participant average of radial and angular response biases in each condition, with trials grouped into tertiles of increasing time constant τ. Error bars denote ±1 SEM across participants (n = 8).