There is no real science behind it, but Evolve creative director Chris Ashton believes that 4 players is the sweet spot for co-op multiplayer games such as Evolve and Left 4 Dead.
Ashton reached that conclusion while working on Left 4 Dead back when it was just a Counter Strike mod. When Valve acquired Left 4 Dead, they wanted to increase the number of team members, but it never felt as good. Needless to say, Left 4 Dead shipped with 4 playable characters and remains so.
"What happens is there's a weird thing in that most people I think are able to track three friends," explained Ashton. "I can know that you're over here and you're in front of me and you're to my left. And I can keep that in my mind, and I can keep in my mind that you have 50 health and you have 80 health, and I can keep track of that and fight another team. But if it's four guys, it feels like I'm always losing one. I always don't know where someone is, I don't know where somebody's health is – keeping track of four other friends is too much."
On the other side of the battle, the super powered monster will be at a disadvantage trying to keep tabs on all four enemies. "That's what makes it a challenge for him," Ashton believes. "As soon as you kill one guy and get one guy out of the picture, I think three humans are way easier to deal with and keep mental tabs on."
