The most well known cry it out technique is the one developed by pediatrician Richard Ferber, director of the Center for Pediatric Sleep Disorders at Children's Hospital Boston. Ferber says that in order to fall asleep on their own and sleep through the night, babies have to learn to soothe themselves. Ferber believes that teaching a baby to soothe himself may involve leaving him alone to cry for prescribed periods of time.
The idea behind extinction (or full extinction to differentiate it from graduated extinction) is that you want to extinguish the behaviour (crying) by not responding to it. As with the check-and-console method, go through your bedtime routine, put them in their crib awake, say good night and walk out. This is certainly the most controversial sleep-training method, and even experts disagree on what you should do next—it all depends on what stage your baby is at developmentally, as well as what works for the parents.
"By the time your baby is 3 months old and has developed a fairly predictable 24-hour pattern, it becomes more important for you to provide increasingly consistent structure. If you do your best to establish a reasonable and consistent daily routine and keep to it as much as possible, then it is likely that your child will continue to develop good patterns. If instead you allow the times of your child's feedings, playtimes, baths, and other activities to change constantly, chances are his sleep will become irregular as well."
"My 3-month-old doesn't sleep through the night, and it's fine with me. I keep her in her crib or a bassinet until her 3 a.m. feeding, and then she joins my husband and me until we get up for work. She won't go in her crib unless she's already asleep, usually from nursing and rocking, but she'll fall asleep in her bassinet beside our bed. She's happy and we're happy, and even if it goes against the wisdom of the experts, it's working for us."
After going through your bedtime routine, put your baby in their crib, leave the room and wait a specific amount of time (say, a minute). Then go in and reassure your baby with words like “Mommy loves you” or some kind of touch, such as a rub or pat. McGinn says it’s preferable not to pick the baby up. Garden, on the other hand, reserves this method for babies seven months and older. (In her opinion, younger babies require a parental presence so they know they haven’t been abandoned, especially if they’ve worked themselves up into a frenzy.)