On manipulating motion gain in immersive virtual environments: An unidentified source of external noise and a new psychometric function

Freeman, Tom C. A. ORCID: https://orcid.org/0000-0002-5989-9183, Haynes, Joshua D., Gallagher, Maria and Culling, John F. ORCID: https://orcid.org/0000-0003-1107-9802 2026. On manipulating motion gain in immersive virtual environments: An unidentified source of external noise and a new psychometric function. Journal of Vision 26 (6) , 9. 10.1167/jov.26.6.9

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Abstract

In immersive virtual environments and other interactive settings the motion gain linking stimulus motion to self-movement is often manipulated to study perceptual performance. We show that this introduces a previously unidentified source of external noise we term gain-dependent noise. The noise arises from trial-to-trial variability in self-movement and can distort the shape of the psychometric function. This leads to overestimates of threshold and sensory measurement noise, and misinterpreted lapse rates when fitting standard sigmoidal functions like a cumulative Gaussian. Using a model observer with minimal assumptions, simulations show the situation is more critical when the coefficient of variation of self-movement (i.e., across-trial standard deviation/mean) is relatively high, and measurement noise associated with image-based and idiothetic signals is relatively low. We derive a new gain-dependent psychometric function that separates sensory measurement noise from gain-dependent noise, and provide a MATLAB fitting routine (fitgdpmf).

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Psychology
Publisher:	Association for Research in Vision and Ophthalmology
ISSN:	1534-7362
Date of First Compliant Deposit:	8 July 2026
Last Modified:	08 Jul 2026 08:15
URI:	https://orca.cardiff.ac.uk/id/eprint/188054

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