Measuring Velocity Perception Regarding Stimulus Eccentricity

ACM Symposium on Applied Perception (SAP), 2024

Abstract

A major factor resulting in cybersickness is the feeling of self-motion experienced when viewing a moving scene in Virtual Reality (VR). Current research indicates that this effect is largely created by motion in the periphery. To discover why this is the case, we investigate the influence of temporal frequency and eccentricity of a stimulus on the magnitude of perceived velocity in the periphery. Based on the perception of two-dimensional stimuli on a wide field-of-view display, we build a model to predict the scaling factor by which the perceived velocity of visual patterns deviates from the physical velocity. Further, our exploratory findings indicate no impact of gaze type on the results, suggesting our model works for both fixation and smooth pursuit scenarios. In an additional pilot study in Virtual Reality (VR), we test the accuracy of the model to predict unnoticeable object motion adaptation in 3D virtual worlds and find positive indications for a similar effect.

Experimental Design

In our main experiment, we investigate the relationship between stimulus eccentricity and perceived velocity of an object by presenting participants with Gabor patch stimuli at different eccentricities while observing and matching a central stimulus. During the entire experiment, participants are unable to observe the peripheral Gabor patch directly. We ensure this by using an eye tracker to blank the entire screen when a participant is no longer looking at the central Gabor patch.

To investigate the influence of gaze type on the model, we repeat select trials of the main experiment while showing a permanent fixation target in the middle of the central Gabor patch.

Results

We found that the perceived velocity of a stimulus not only depends on its eccentricity, but this effect changes depending on the velocity of the stimulus itself. Concretely, for slower speeds the velocity is overestimated the further the stimulus lies in a participant’s periphery, whereas for faster speeds the velocity of the stimulus is underestimated. By combining these findings, we propose an empirical model to describe this relationship:

Using the secondary experiment we confirmed this model to hold for both fixation and smooth pursuit gaze types. Our VR pilot study suggests that this effect exists in more complex scenarios as well, and highlights further opportunities to fine-tune the model.

Citation

@inproceedings{scholz2024measuring,
  title = {Measuring Velocity Perception Regarding Stimulus Eccentricity},
  author = {Scholz, Timon and Groth, Colin and Castillo, Susana  and Eisemann, Martin and Magnor, Marcus},
  booktitle = {Proc. {ACM} Symposium on Applied Perception ({SAP})},
  isbn = {9798400710612},
  doi = {10.1145/3675231.3675234},
  number = {4},
  pages = {1--9},
  month = {Aug},
  year = {2024}
}

Acknowledgements

The authors gratefully acknowledge partial funding by the DFG (MA2555/17-1, "Real-Action VR: Immersive Experience of ActionCam Video Recordings", Project number 523421583).