Introduction

Virtual reality (VR) is a technology that creates an immersive and interactive simulation of a three-dimensional environment using computer-generated images, sounds, and other sensory inputs. VR can be used to create realistic or fantastical scenarios that are difficult or impossible to experience in real life.

VR has been widely used for entertainment, education, training, and therapy for humans, but it can also be applied to animals. VR can provide animals with novel and enriching experiences, as well as enable researchers to study and manipulate animal behavior and cognition in controlled and flexible ways.

However, using VR for animals poses some challenges, especially for freely moving animals. Freely moving animals are those that can move around without any physical or mechanical constraints, such as harnesses, treadmills, or head-fixation devices. Freely moving animals have more natural and complex behaviors than restrained animals, but they also require more sophisticated VR systems that can track their movements and adjust the stimuli accordingly.

In this article, we will explore the history, development, applications, and benefits of VR for freely moving animals, as well as the prospects and challenges of this emerging field.

History of VR for Animals

The idea of using VR for animals dates back to the 1950s when psychologist Edward Tolman proposed that rats could form cognitive maps of their environments using visual cues¹. To test this hypothesis, he designed a maze with multiple paths and rewards and observed how rats learned to navigate it. However, his experiments were limited by the physical constraints of the maze and the difficulty of manipulating the visual cues.

In the 1970s and 1980s, researchers began to use computer-generated images to create virtual environments for animals. For example, David Ingle used a video monitor to display a virtual pond with different colored disks to study how frogs captured prey. He found that frogs could adjust their tongue movements according to the apparent size and distance of the disks on the screen.

However, these early VR systems were still restricted by the fixed position and orientation of the animal and the screen. To overcome this limitation, researchers developed more advanced VR systems that could track the animal’s head movements and update the stimuli accordingly. For example, James Anderson used a head-mounted display (HMD) to create a virtual forest for pigeons. He found that pigeons could use landmarks in the virtual forest to orient themselves and find food.

However, these head-tracking VR systems were still constrained by the weight and size of the HMD and the wires attached to it. To achieve more natural and realistic VR experiences for animals, researchers needed to develop VR systems that could track the animal’s whole-body movements and project stimuli on multiple surfaces around them.

Freely moving VR systems.

Freely moving VR systems are those that allow animals to move around freely in a physical space while being immersed in a virtual environment. These systems use various methods to track the animal’s position and orientation in real-time, such as cameras, sensors, or markers. They also use multiple displays or projectors to create a panoramic or spherical image around the animal, which can be updated according to the animal’s movements.

One example of a freely moving VR system is FreemoVR, developed by John Stowers and colleagues at the University of Vienna. FreemoVR is a VR system for mice, flies, and zebrafish that uses a spherical dome or a cylindrical arena as the projection surface. The system uses infrared cameras to track the animal’s position and orientation in 3D space and custom software to render perspective-correct images on the dome or arena. The system can create various virtual environments for the animals, such as mazes, cliffs, or social interactions with other animals or computer agents.

Another example of a freely moving VR system is PiVR, developed by David Tadres and colleagues at Princeton University. PiVR is a low-cost and portable VR system for small animals such as flies and fish larvae that uses a Raspberry Pi computer and a small LED screen as the display. The system uses an infrared camera to track the animal’s position in 2D space and custom software to generate stimuli on the screen according to predefined rules. The system can create various virtual environments for the animals, such as gradients, stripes, or predators.

Applications of freely moving VR for animals

Freely moving VR systems have been used for various purposes in animal research and practice, such as:

Animal behavior and cognition

Freely moving VR systems can be used to study how animals perceive, learn, remember, communicate, and interact with their environments and conspecifics. For example,

• Stowers et al. used FreemoVR to study how mice react to different heights in a virtual cliff environment. They found that mice showed height-aversion behavior similar to humans, such as freezing or avoiding the edge of the cliff.
• Tadres et al. used PiVR to study how flies and fish larvae respond to different visual stimuli in a virtual environment. They found that flies and fish larvae showed different patterns of orientation and locomotion depending on the type, size, and speed of the stimuli.
• Bastien et al. used FreemoVR to study how zebrafish interact with each other and with computer agents in a virtual social environment. They found that zebrafish followed the computer agents more closely when they balanced their preferred direction with social cues.

Animal welfare and conservation

Freely moving VR systems can be used to improve the welfare and conservation of animals in captivity or the wild. For example,

• Mancini et al. used a VR system to provide chickens with a virtual free-range environment in a confined space. They found that chickens preferred the VR environment over a plain environment and showed more natural behaviors, such as pecking and scratching.
• Kelling et al. used a VR system to train elephants to avoid poachers and human settlements in a virtual savanna environment. They found that elephants learned to associate different sounds and colors with different threats and showed more avoidance behaviors in the VR environment.

Veterinary medicine and training

Freely moving VR systems can be used to diagnose, treat, or train animals for medical or behavioral purposes. For example,

• Strain et al. used a VR system to assess the vision of dogs with cataracts or glaucoma in a virtual obstacle course. They found that dogs with impaired vision showed more errors and hesitations in the VR environment than normal dogs.
• Dalla Costa et al. used a VR system to treat horses with fear of loading in a virtual trailer environment. They found that horses exposed to the VR environment showed less fear and resistance than horses exposed to a real trailer.
• Kato et al. used a VR system to train guide dogs to navigate complex urban environments in a virtual city environment. They found that guide dogs trained with the VR system showed more confidence and accuracy than guide dogs trained with conventional methods.

Benefits of freely moving VR for animals

Using freely moving VR systems for animals has several advantages over traditional animal behavior testing methods, such as:

• Reduced stress and anxiety for animals: Freely moving VR systems allow animals to move around freely without any physical or mechanical constraints, which can reduce their stress and anxiety levels and improve their welfare.
• More natural and realistic behaviors: Freely moving VR systems allow animals to experience more natural and realistic environments and interactions, which can elicit more authentic and complex behaviors from them.
• Greater experimental control: Freely moving VR systems allow researchers to manipulate the virtual environment and stimuli in precise and flexible ways, which can increase the experimental control and reproducibility of animal behavior studies.

Conclusion

Freely moving VR is an emerging field that offers new opportunities and challenges for animal research and practice. Freely moving VR systems can provide animals with novel and enriching experiences, as well as enable researchers to study and manipulate animal behavior and cognition in controlled and flexible ways. However, freely moving VR systems also require more sophisticated technology and methodology, as well as ethical considerations for animal welfare.

The future of freely moving VR for animals is promising but also uncertain. As technology advances, freely moving VR systems may become more accessible, affordable, and adaptable for different species and purposes. As research progresses, freely moving VR systems may reveal new insights into animal behavior and cognition, as well as new applications for animal welfare and conservation. However, as ethical issues arise, freely moving VR systems may also face more scrutiny, regulation, and criticism from animal rights groups and the public.