The role of visual contextual cues on motion extrapolation: A single horizon line biases the Representational Horizon

The perceived offset position of a moving target is systematically displaced forward, in the direction of motion (Representational Momentum; RM), downward, in the direction of gravity (Representational Gravity; RG), and along the horizon implied by the visual context (Representational Horizon; RH). The latter has been shown to depend on visual context orientation, particularly in exterior settings where horizon cues are salient. Building on this evidence, the present study examined whether RH can be reliably biased by minimal visual cues that efficiently imply a horizon axis and investigated their differential impact on motion extrapolation phenomena. Participants observed moving targets following various trajectories, overlaid on a randomly chosen visual context depicting either a combined ground and sky gradients, an isolated ground or sky gradient, or a single horizon line context rotated -22.5º, 0º, or 22.5º relative to the true vertical. Upon the target's vanishing, participants indicated its last seen location with a trackball. Spatial localizations were subjected to a discrete Fourier decomposition procedure to obtain independent estimates of RM, RG, and RH. Outcomes showed that RH direction consistently followed the horizon implied by the visual context across all conditions. Furthermore, RM magnitude increased with the sky gradient and decreased with the ground gradient, indicating sensitivity to ecological features. These findings underscore the pivotal role of horizon information in visuospatial orientation and contribute to a better understanding of extrapolation phenomena.