Watch Dogs won't start with 4 GB of RAM.
Watch Dogs Creative Director Jonathan Morin revealed on Twitter that the Windows PC version of that game requires at least 6 GB of RAM.
@Design_Cave CPU - Intel i3 3210 @ #.2 GHz GPU - Geforce GTX 650 2B OC edition. Ram -4 GB So.. any idea about my specs? [Low / Medium??]
— Ashfaq Nawaz (@AshfaqNawaz) May 17, 2014
@AshfaqNawaz The main issue is your ram. If you climb it up to 6 you should be able to run the game at low settings.
— Jonathan Morin (@Design_Cave) May 19, 2014
Morin also revealed that Watch Dogs is coded to depend mostly on the CPU than the GPU during gameplay.