Immersive virtual worlds like The Sims and World of Warcraft are as popular as ever— for the latter game alone, almost 10 million subscribers design their own role-playing avatars to interact with each other in an alternate online reality.

New research presented today at this year's Conference on Human Factors in Computing Systems suggests that designing and modifying these virtual reality avatars is even more interactive than one might think— making physical alterations to their avatars can actually affect how people perceive their virtual environments and start to meld their identities with their digital characters.

The study asked 121 college students from Sungkyunkwan University in South Korea to participate in a computerized experiment using virtual reality avatars.

In a virtual environment with three hills of different heights and steepness, one group of participants was assigned a random hiking avatar and the other group was allowed to customize their own. Half of the avatars in each group wore backpacks, and the other did not. Researchers told the ones with backpacked characters that the bags made the hiking experience more realistic. All of the students were asked to judge the difficulty of climbing the hills.

The idea was to see whether a digital avatar's backpack led participants to overestimate the height and incline of virtual hills, as people tend to when traveling across real terrain while carrying real weight on their backs.

Indeed, the findings revealed that seeing a virtual reality avatar's backpack made participants more likely to judge hills as higher and more difficult to hike. In addition, participants who designed their own avatars perceived the hills as higher, steeper, and requiring more energy to climb than those who were assigned characters.

"You exert more of your agency through an avatar when you design it yourself," explained Penn State media researcher S. Shyam Sundar in a press statement. "Your identity mixes in with the identity of that avatar and, as a result, your visual perception of the virtual environment is colored by the physical resources of your avatar."

That might seem intuitive to gamers, but the study results show a marked effect. Participants whose characters carried backpacks felt like the characters would have a harder time hiking up the hill, but much more so if they customized the avatar themselves.

The findings aren't useful just for game developers, who have a clear interest in drawing in gamers with more flexible and customizable avatar designs.

Virtual reality rehabilitation for people with physical disabilities, for example, could be more realistic and immersive if patients are allowed to design their own avatars.

Digital avatars could also empower people with PTSD— the United States is already funding virtual reality therapy for the anxiety disorder, and customizable avatars could strengthen virtual world interactions to overcome real-life anxieties.

"Because building avatar identity is critical, it's important to let users customize it," said Sundar. "You are your avatar when it is customized."