According to FAA Advisory Circular AC No: 61-115, all pilots and specifically student pilots, instructors and pilot examiners should use specific procedures to establish a positive exchange of flight controls. Using these procedures both pilots always know exactly who is flying the plane at all times.
For instance, if the flight instructor is giving the flight controls to the student the flight instructor says, "You have the flight controls." The student then takes the flight controls and says, "I have the flight controls." The flight instructor visually checks to make sure the student has the flight controls and then says "You have the flight controls."
If the flight instructor needs to take the flight controls they start the process by saying: "I have the flight controls." Student: "You have the flight controls." Instructor: "I have the flight controls."
While visiting my brother, his lovely wife and their newborn baby in April, I observed how very carefully people would hand the baby between each other. It was never totally clear who had the baby at any given time. So people had to be very careful as they gave each other the baby. My husband and I discussed perhaps proper Positive Exchange of Baby procedures would be helpful in these situations.
For instance, if my sister-in-law were to give the baby to her sister to hold her for a while, she could start the process by saying, "You have the baby." Once the sister had the baby safely and totally supported by her hands, the sister could say, "I have the baby." My sister-in-law could complete the process by saying, "You have the baby."
If the baby became upset and wanted to go back to mommy my sister-in-law could say, calmly but firmly, "I have the baby." at which point the sister would gladly comply by saying "You have the baby." and once my sister-in-law definitely had the baby in hand she would complete the process: "I have the baby."
Think about it... I think this should be taught in all new parent classes ;)