SAN DIEGO—You are guiding a ship through rough waters. On your way you may encounter magical creatures. You can snap a photo or two, but your main job is to navigate the maze of waterways to find missing pieces of a long-lost journal. You might get lost occasionally, but that’s all right. After all, this is just a mobile game and the scientists behind it are tracking your performance to measure how people of all ages compare in their spatial navigation abilities.

The ultimate goal is to use this data to spot navigation problems early on in millions of people afflicted with dementia, hoping this might lead to better tests for the devastating illness. “By creating a global chart of human spatial navigation, we’d like to create the next set of tools for the diagnosis of Alzheimer's,” says neuroscientist Hugo Spiers of University College London, one of the scientists behind the mobile app game Sea Hero Quest. Spiers presented the results of the first rounds of analysis this week at the Society for Neuroscience’s annual meeting in San Diego. The preliminary findings provide a baseline measure of navigation ability in healthy people, revealing variations based on age, sex and home country.

“There are many features of dementia that are either noncognitive or not easily or routinely measured—such as changes in gait, in neuropsychiatric symptoms or in behavior—that can give hints as to underlying disease,” says Zahinoor Ismail, a neuropsychiatrist at the University of Calgary who was not involved with the research. “Orientation and navigation may be one of those features, and a reliable way to measure it could be useful in early detection or monitoring change over time.”

Spatial navigation relies on brain regions that are commonly affected by the early stages of Alzheimer’s disease. Before severe and obvious memory problems set in and people are diagnosed with dementia, they might report problems with finding their way around and frequently get lost in familiar neighborhoods. In that early stage, however, it is difficult to know whether their impaired navigational skills are actually due to the disease or simply a part of normal aging—because we currently don’t have a firm grasp on what “normal” is.

In their recent study, Spiers and his colleagues aimed to change that by establishing a standard of human spatial navigation ability—a little like growth charts for children but instead establishing a common baseline for adults’ navigational skills, which naturally decline with age. For that, the researchers needed large numbers of people—hence the idea for crowdsourcing the experiment via gaming.

Navigating inside a game may not be exactly the same as finding one’s way in a real-world situation. But people are likely to use the same cognitive mechanisms in both situations, and recent research suggests levels of performance in both are tightly correlated. “If you are good at navigating, you'll do well in the game. And if you are bad at finding your way out there, you'll also struggle in the video game,” Spiers says, adding that their team still plans to compare the game performance with real-life performance in near future.

Since its launch in May, some 2.5 million people have played Sea Hero Quest (although not everyone finished all the levels of the game, data from each level can be analyzed separately), making it one of the most impressive scientific experiments to date just by the sheer number of participants. “To my knowledge, never before has spatial navigation been quantified on such a large scale,” says Katherine Possin, an assistant professor of neuropsychology at the University of California, San Francisco, who was not involved with the research. “I hope that these researchers will have the opportunity to follow these individuals to measure changes in performance over time, and how they may predict conversion to mild cognitive impairment or Alzheimer’s disease.”

So far one of the main findings coming out of Sea Hero Quest is a simple linear decline with age: From the age 19 onward, spatial navigation steadily worsens from year to year. The 19-year-olds were able to remember their starting point and accurately hit it by shooting a flare back to that position 74 percent of the time. Those aged 75 succeeded only 46 percent of the time.

Another finding is that men appear to perform better than women on these specific tasks. Although this finding seems to fit with the long-held assumption that men are better navigators, rather it may reflect that males have more experience with games. The researchers tried to account for this possibility, yet still found a gender difference in performance. Spiers notes, however, that the games boys and girls play in early childhood—which could influence brain development and spatial skills—are much harder to account for.

The researcher also found a link between navigational skills and where participants lived. Players from Nordic countries such as Finland, Sweden, Norway and Denmark showed the highest navigational skills among players from more than 190 nations. Next came people from Australia and New Zealand, and then those from other northern European countries. “The question is why. And we don’t have an answer yet,” Spiers says. “We are really skimming the surface. There's so much data from everyone who's played the game and has given so much of their time and energy. We have two years of analysis ahead of us.”

Next summer the team plans to begin testing dementia patients to match them against navigational skills in the healthy population. Such a test could also offer an advantage over the language-based memory tests currently used in the clinic, by allowing researchers to compare people from one country with another without worrying about potential confounding factors due to different languages. “We are hoping that this not only would help target primary initial symptoms in patients, but also provide a generally language-free test that can be done anywhere,” Spiers says.