A good friend shared this site with me and I just had to share it with you! This is an excellent resource for parents to help understand a newborns behaviour, yes...even the periods of cyring where nothing you do seems to help them stop crying.
Here is an excerpt from the website, but I encourage you to go exploring thru the many articles and videos!
"......The Period of PURPLE Crying begins at about 2 weeks of age and continues until about 3-4 months of age. There are other common characteristics of this phase, or period, which are better described by the acronym PURPLE. All babies go through this period. It is during this time that some babies can cry a lot and some far less, but they all go through it.
"Scientists decided to look at different animal species to see if they go through this developmental stage. So far, all breast feeding animals tested do have a similar developmental stage of crying more in the first months of life as human babies do."
Scientists, including developmental pediatricians, have conducted studies worldwide on early infant crying over the course of many decades....."