"At the same time, our industry has experienced continuing and fundamental change which affects how we all create, and play, games.
"Delivering the immersive, narrative-driven stories that PlayStation Studios is known for, at the quality bar that we aspire to, requires a re-evaluation of how we operate."
PlayStation Studios has grown to deliver "social, online experiences" as well as launching games on PC and mobile. However, "growth itself is not an ambition".
"We looked at our studios and our portfolio, evaluating projects in various stages of development, and have decided that some of those projects will not move forward," said Hulst.
"I want to be clear that the decision to stop work on these projects is not a reflection on the talent or passion of team members.
"Our philosophy has always been to allow creative experimentation. Sometimes, great ideas don't become great games. Sometimes, a project is started with the best intentions before shifts within the market or industry result in a change of plan.
"I am deeply saddened to see talented individuals leave the company. I have so much admiration, appreciation and respect for their work."