Arachnophobia is among the most common phobias and can have upsetting consequences, from panic attacks to arachnophobes avoiding everyday occasions due to fear of encountering a spider.

A well-established treatment for arachnophobia and similar phobias is exposure therapy, in which patients are guided by a therapist through more and more stimulating or realistic exposures to their fear. For instance, the patient may begin by looking at a cartoon spider and progress to handling a tarantula.

Arachnophobes can be reluctant to partake in exposure therapy, however, due to fear of exposing themselves to real spiders towards the end of treatment. Hoping to reassure arachnophobes, the Basel team developed an AR app, Phobys, based on established principles of exposure therapy: “It’s easier for people with a fear of spiders to face a virtual spider than a real one,” explained Anja Zimmer, who led the study.

The app projects a realistic 3D spider model onto the user’s background as captured through their phone camera. It has nine different levels of exposure, challenging the user to get close to, and eventually interact with, the virtual spider. It makes use of game elements, such as rewarding feedback, animation, and sound effects.

Each level ends with a self-assessment of fear and disgust. Once the user’s fear response has been dampened, they can move on to the next, more intense, level.

Zimmer and her colleagues put Phobys to the test in a clinical trial involving 66 arachnophobic participants. Over two weeks, the participants either completed six half-hour training units with the app or, for the control group, had no intervention.

Before and after treatment, they were asked to approach a real spider in a transparent box as closely as their fear would allow: the group that had used Phobys showed significantly less fear and disgust towards the real spider and was able to move closer than the control group.

The researchers worked with a spin-off from the University of Basel, MindGuide at GeneGuide AG, to refine their app. It is now available as a freemium app in the App Store and Play Store for people with mild fear of spiders to use alone; users with severe arachnophobia are not advised to use Phobys without supervision from a professional.

In 2013, another spider-related app, Phobia Free, based on similar principles – using exposure to spiders to reduce arachnophobia, although not including the AR elements of Phobys – was approved by NHS England to feature in its app library. All apps in the NHS library can be considered clinically safe. University of Kent researchers have incorporated exposure therapy into VR to provide tools to help patients with eating disorders, part of a wider move towards adoption of extended-reality technologies to supplement traditional psychological therapies.