Not that much has been written about out of sight stays. Twenty years ago, we were all told to correct a dog that broke his stays when you left the room harder and harder. .. get the point across. I left 198 performances in the ring over and over because my dog wouldn't or couldn't manage an out of sight stay. Today, I would have said the dog had separation anxiety; a confidence problem ... one that I was making worse every time I corrected her or had someone else correct her while I was gone. That just adds fear of other people to the stress the dog already had. With regrets come chances to look at the exercise and the next dog differently. I have several ideas that are working pretty well. Maybe they will be what your own Newfoundland needs.
This dog remains attentive (and down) during out of sight stays at the 1999 National
Let's say that your dog does a lovely sit and/or down stay while you are across the ring in obedience, water or draft training. My next step is to leave the dog on a stay and just move around. This is totally different from my standing in the fixed and usual spot several feet away like a statute. Take care of things that need to be done in the same area while he does his stay. At different time frames, walk up to him and tell him how good he is to "sit and stay", or to "down stay". Then resume the activity. Work up to several minutes. Don't insist your dog "watch" you. He cannot do so when you leave the room, which would just add to his stress if he is told he is supposed to keep you in his sights.
When he is totally confident about staying while I do other things in the same area, I repeat the stay command after he has relaxed with me moving around and then leave the room; just for a moment or two. I might put a few things away from the laundry basket; then come right back, praise him, and then do it again. I might praise him verbally from the next room for "staying" while I count off several seconds. I repeat the leaving and coming back steps gradually for many sessions. My entire goal is that he will be comfortable with his stay, trusting that I will be back, and that we will both be pleased with him when I return.
If he has a problem at any point, I go back to helping him with his stays in sight. Never again will I risk a confidence problem with a dog on out of sight stays. I go back to where I could praise the dog for being right instead of trying to catch him being wrong. There are a few things I will not work up to, under any circumstances because I think it breaks his trust in me: I will not leave him by opening a closed door to go outside my home and then close the door behind me. If I go out briefly, I leave the door open, praise him for staying, come right back, etc. I also do NOT pick up my keys, put on my coat, or do anything that gives my dog the impression that I'm leaving or abandoning him. I always want him to know that leaving is only temporary ... no cause to worry ... that he can trust me. When I get to the point that I try to leave him in other places, such as obedience class, I go through the same motions. Occasionally, I see a dog who shows signs of stress when left in a public place that doesn't seem to improve. In those cases I provide a babysitter. That person praises him with me, then for me while I am silent in the same room, then again for me while I move around the room. Under no circumstances does that person correct the dog. If the dog is breaking at that point, I need to go back to remedial stays with praise in the same room and stay there for a while longer. When my dog will take the random praise from the babysitter and appears comfortable in his stays, I go back through the motions of leaving briefly, having the designated person praise him for staying, then I come back and praise as well. At some point, the babysitter should be able to just stand in the same room while my dog stays confidently until I get back to heel position. Now, the dog will look upon people in and outside the ring as benevolent and helpful, rather than punitive.
One last word, when someone else comes back to correct THEIR dog for breaking, either I or the babysitter always returns to my dog and praises verbally and/or with our hands to let him know how proud we are that HE is staying at the same time as the other dog may be getting a correction. If, at any time, my dog is frightened and breaks, either the babysitter or I can just gently put the dog back in position and praise again while the dog holds the stay briefly.