The major studies that have been done are fairly easy to find with some google investigation. I looked at them all over a year ago and formed my conclusions. I

The major studies that have been done are fairly easy to find with some google investigation. I looked at them all over a year ago and formed my conclusions. I unfortunately didn't keep around a list of links to post in debates on internet forums. This post mentions a few of the main ones (I'm not vouching for the post's content): https://www.laleche.org.uk/letting-babies-cry-facts-behind-studies/ https://www.laleche.org.uk/letting-babies-cry-facts-behind-s...