Article-Journal

From discomfort to danger: Exploring how affective obstacle properties influence avoidance in stepping

Stepping over obstacles requires adjusting the foot trajectory to avoid contact with surfaces that may be hazardous or unpleasant to step on. While it is well established that obstacle height and stability influence stepping behaviour, little is known about how perceptual affective evaluations, such as dangerousness, unpleasantness, and painfulness, modulate avoidance strategies. In Experiment 1 (N = 20), participants stepped over obstacles covered with stones varying in size and density while rating their perceived unpleasantness. Visual uncertainty was manipulated by comparing monocular and binocular viewing. Lead minimum foot clearance (MFC) was initially higher under monocular vision but decreased to binocular levels over trials. While obstacle unpleasantness did not systematically affect MFC or crossing step length, perceived unpleasantness ratings correlated weakly with crossing step length. However, because dangerousness and painfulness ratings were not collected, it remained unclear whether unpleasantness directly influenced avoidance behaviour or served as a proxy for perceived risk. To address this, Experiment 2 (N = 22) introduced obstacles covered with metal stud spikes or smooth surfaces, with additional ratings of dangerousness and painfulness. Results showed that MFC was higher for spiky than smooth obstacles. Crucially, in this experiment, ratings of perceived dangerousness, not unpleasantness, correlated positively with crossing step length, after controlling for other perceptual ratings. These findings suggest that perceptual affective properties modulate avoidance parameters. However, the nature of those modulations is stimulus specific and highly depends on task demands.

Aug 10, 2025

Obstacle avoidance of physical, stereoscopic, and pictorial objects

Simulated environments, e.g., virtual or augmented reality environments, are becoming increasingly popular for the investigation and training of motor actions. Yet, so far it remains unclear if results of research and training in those environments transfer in the expected way to natural environments. Here, we investigated the types of visual cues that are required to ensure naturalistic hand movements in simulated environments. We compared obstacle avoidance of physical objects with obstacle avoidance of closely matched 2D and 3D images of the physical objects. Participants were asked to reach towards a target position without colliding with obstacles of varying height that were placed in the movement path. Using a pre-test post-test design, we tested obstacle avoidance for 2D and 3D images of obstacles both before and after exposure to the physical obstacles. Consistent with previous findings, we found that participants initially underestimated the magnitude differences between the obstacles, but after exposure to the physical obstacles avoidance performance for the 3D images became similar to performance for the physical obstacles. No such change was found for 2D images. Our findings highlight the importance of disparity cues for naturalistic motor actions in personal space. Furthermore, they suggest that the observed change in obstacle avoidance for 3D images resulted from a calibration of the disparity cues in the 3D images using an accurate estimate of the egocentric distance to the obstacles gained from the interaction with the physical obstacles.

Jun 1, 2025

No evidence for top-down expertise effects on action perception in sprinters using static images