In 2011, a group of MIT researchers asked people on the internet to to play a game. They took two geo-tagged photos of different streets from Google Street View and placed them side-by-side. Then they asked the users: Which one looks safer? Livelier? More depressing? Once a user answered, a new set of photos would appear.
The project, which is ongoing, is called Place Pulse, and as CityLab reported then, it was used to study how people perceived the safety of a street based on the appearance of buildings, the presence of trees, and how the sidewalks looked. Fast forward about five years, and more than 80,000 people from around the world have participated, resulting in more than 1.3 million clicks on more than 100,000 photos.