It has sparked a major debate online.

An economics professor and author of a new book called Cribsheet has been criticised online after she said she believes a baby should be left to cry. Emily Oster claims that leaving a baby bawling will not cause it to have developmental damage in the future and will make them sleep more soundly. The Brown University professor says that her research shows that parents are making babies worse when they check on them every time they let out a whimper. However, parents are upset by the claims, saying that 'sleep training' can work on some and not on others, which is why you shouldn't force the idea on every mum and dad - it's all about what works for the baby.

I had a very snobbish view of sleep training when my oldest quickly complied with the protocol. My younger taught me humility though as she would cry until vomiting, lost all “sleep training” with cold and started climbing out of her crib at 18 months. What works varies by kid.

— Jenny Silva (@signupforcamp) June 2, 2019

I just don’t understand how you could sit and listen to your baby cry?! Surely a lack of emotional intelligence if you can do that?! Really disappointing to read this. ☹️

— Kirsty Roberts (@Kirstyir89x) June 2, 2019

I see comments here aren't so negative, so I wonder are some of them deleted. Leaving small child to cry just sends them message that they are helpless and on one cares about them. I also don't know since when is Economy PhD expert for this topic.

— IT job site Rep.hr (@rephr) June 4, 2019

Sleep training is absolute baloney. Total total total total baloney.

— Sarah MacKinlay (@sarahmackinlay) June 2, 2019

my role as a parent is to respond to my baby’s needs. If they’re crying, they need something - food, drink, too hot, too cold or just a cuddle. If I woke up upset in the night, I’d hope I wouldn’t be ignored and left ?? https://t.co/Fr678FQKAc

— Rachel (@coffee_cakekids) June 2, 2019

It brings to mind the bad old days with books that contained harmful 'guidance' that condoned such harmful practices which parents duly followed. It is NOT advisable on any level to leave a baby to cry until she gives up hope & falls silent. I don't care who the book's author is.

— Mine Conkbayir (@MineEYMind) June 3, 2019

Have you tried sleep training? Did you find it worked? Or were you not able to go through so many minutes listening to your baby cry?