Needing a published study to tell us a baby (or any one of us, for that matter) will be distressed if we shut him in a room alone and don’t respond to his cries, is like needing research to tell us the grass will grow if it rains. While there is certainly a difference in physical safety between checking on a crying baby and shutting the door overnight, there are no ‘published studies’ telling us how long it is ‘safe’ to leave a baby to cry.