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.
"I have a 3-month-old who I rock at night. He falls asleep very quickly (much quicker than if I leave him in his crib). If he wakes in the middle of the night, we go to him and comfort him. We don't take him out – we just help soothe him. Why make him feel lonely and abandoned? I have no problem losing a little sleep if it means that he feels like we will be there for him."
If you have a hard time remembering how many times your baby woke last night, much less how she slept last week, a log will help you notice patterns. After a week of tracking her days and nights, start by figuring out her ideal bedtime. You might say, "Oh, she's always fussy at 7 p.m.—that's probably when I should be putting her down, and I'm missing the window." A log will also let you see that your baby may not have cried during the night for as long as you thought. Five minutes of fussing can feel like 50 when it's 2 a.m.
Most sleep coaches say the ideal time to start sleep training (or promote independent sleep, not necessarily using the cry-it-out method) is based on your baby’s development, but is usually somewhere between four and six months, when your baby hasn’t had much time to get used to nursing or rocking to sleep. At this stage, most babies are also developmentally ready to learn the skill of falling asleep on their own, explains Jennifer Garden, an occupational therapist who runs Sleepdreams in Vancouver. Around four months of age, some babies go through a sleep regression because their sleep cycles change and there are longer periods of lighter sleep per cycle. “It’s a great time to work on independent sleep skills,” says McGinn. Other babies’ slumber derails around this time because they are working on new skills, like moving around and rolling. Some parents choose to wait until things settle down before embarking on a sleep-training method, but you don’t have to, says McGinn.