Sex and Age Differences in Virtual Reality (VR) Sickness Susceptibility in Forklift Driving Simulation

Abstract

Traditional forklift training methods are limited by their time-consuming nature and high costs. Virtual reality (VR) simulators have emerged as a cost-effective and safe alternative for forklift driving training. However, previous research revealed a substantial challenge associated with VR experiences, specifically concerning motion sickness during forklift training. Motion sickness poses a significant challenge to the effectiveness and user experience in VR forklift simulations. The primary objective of this research is to examine the influence of sex and age on motion sickness susceptibility within a virtual reality forklift simulation. Twenty individuals (nine females, eleven males) participated in the study and completed several driving tasks in a VR forklift simulator. Survival analysis (Kaplan-Meier) and Cox Proportional Hazards models examined sex and age differences in VR sickness. Age was the only significant predictor. The effects of age on motion sickness susceptibility highlight the need for tailored approaches in VR development and training.

Operator training in forklift driving is essential to ensure safety and is required by the Occupational Safety Health Administration (OSHA 1910.178 (i)(6)) standards (Sarupuri et al., 2016). Training operators using virtual reality (VR) simulators are a cost-effective alternative to traditional training, which is resource-intensive and costly (Islam et al., 2023; Villiers & Blignaut, 2016). However, motion sickness in VR training is a substantial challenge caused by perceptual conflicts between visual stimuli and vestibular sensations (Oman, 1990; Warwick-Evans et al., 1998). Individual attributes such as sex and age are known to affect motion sickness susceptibility, with females and older adults more prone to symptoms due to variations in vestibular sensitivity, hormonal influences, and cognitive processing (Abouzari et al., 2020; Bannigan et al., 2024; Park et al., 2022). While studies have explored the impact of sex and age in VR driving simulators, specific investigations in the context of forklift driving remain under-researched (Almallah et al., 2021; Brooks et al., 2010). To promote the widespread adoption of VR training in forklift driving, this research aims to investigate how sex and age affect an individual’s susceptibility to motion sickness during a virtual reality forklift simulation. The findings of this study could shed light on the relationship between sex, age, and motion sickness in VR environments for forklift training, ultimately informing the development of tailored interventions and design approaches to improve user comfort and training outcomes.

Twenty participants (nine females, eleven males) were recruited for this study. Participants were categorized into two groups based on age: a younger adult group (18–40 years old; n = 9) with an average age of 26.3 years (SD: 5.1 years), and an older adult group (over 40 years old; n = 11) with an average age of 51.8 years (SD: 8.6 years). Participants provided written informed consent, following the procedures approved by the local Institutional Review Board.

We utilized a VR-based order picker forklift simulator (The Raymond Corporation, NY, USA) equipped with a Vive Pro Eye headset (HTC Corporation, Taiwan) and a Leap Motion controller (Leap Motion Inc., USA), all connected to the physical truck control panel (Islam et al., 2024). After a 10-min training session, participants completed 2 trials of 4 different forklift driving lessons, totaling 8 trials, with 2 to 5 min breaks between each trial. Participants were allowed to remove the VR headset between trials and were asked to complete the Virtual Reality Sickness Questionnaire (VRSQ) after each trial (Kim et al., 2018).

VRSQ responses were analyzed across four subscales: Nausea, Occulomotor, Disorientation, and Overall motion sickness (Kim et al., 2018). We classified trials as either sickness-induced or not based on VRSQ scores. Any trials with VRSQ scores above 30% of the maximum attainable score were regarded as sickness-induced trials. Survival time in the VR simulator was determined by summing the total time spent in VR during trials (excluding break times) until the 30% VRSQ threshold score was reached. Survival analysis (Kaplan-Meier) and Cox Proportional Hazards models were used to investigate the impact of sex and age on VR sickness for each VRSQ subscale and the overall scale. The Kaplan-Meier method estimated survival probabilities over time, allowing comparison of survival curves (time until motion sickness) between age groups and sexes. The Cox model calculated risk ratios for each age and sex group.

Age was the only significant factor influencing susceptibility to motion sickness across all four VRSQ subscales. Older participants demonstrated a substantially higher risk, ranging from 4.2 to 7.8 times greater, of experiencing motion sickness compared to younger participants. There was no significant difference between the sexes or interaction effect between age and sex. Notably, both females and older adults experienced a rapid decline in the probability of remaining sickness-free, with rates dropping to 55.6% and 22.2%, respectively, within the first 10 min of training.

While previous studies showed sex-based differences in motion sickness susceptibility, our investigation did not find sex differences in VR forklift simulation training (Fulvio et al., 2021; Hou et al., 2019). The impact of age on motion sickness indicates a vulnerability among older individuals in VR forklift training. Thus, it is crucial to consider potential mitigation strategies to mitigate motion sickness among older users to reduce discomfort and other adverse health impacts (Lee et al., 2021). In a standing position, as used in the current VR forklift simulator, older adults may experience greater discomfort due to sensory conflicts between VR visual cues and vestibular inputs, increasing their motion sickness risk (Bonnet et al., 2008; Kim et al., 2018). In conclusion, our research found the significance of age in relation to motion sickness within forklift training simulations. We emphasize the need to consider age-related factors in simulator design and implement mitigation strategies to create a more inclusive training environment for users of all ages and demographics. As this study was exploratory in nature, future research incorporating additional subjective and objective measures of motion sickness could provide a more comprehensive understanding of the roles that sex and age play in virtual forklift training experiences.