Having performed an exhaustive search, I cannot find answers to my questions: 1. What is the source for each currently accepted developmental milestone, 2. Where is a comprehensive list of cognitive milestones and tasks, and what are their sources (i.e., who created them, etc.)? I am NOT looking for the list of milestones themselves, but rather, who came up with each one, what study was it based on, etc... I have asked the AAP (no answer), and referenced several pediatric textbooks, and have only found one reference to Linden's milestones or Beck's milestones, each of which were created by the individual's on a study. Am I to understand that all of the currently accepted milestones are all based on a single study by one person on a group of 30 non-culturally diverse children?! Or that anyone can come up with a list of observable tasks and call them milestones?! If anyone knows what the currently accepted milestones are based on, or taken from, please divulge. I am seeking specifics, not generalities (i.e. I am not looking for Piaget, or Skinner; I seek the raw data, the study(ies), and confirmation that they are the current "gold standard") I am looking for the body of information upon which cognitive, motor, etc. assessments are built upon. Thanks!
Some developmental milestones are based on research studies while others are simply just something that was observed through hundred of years. Most physical milestones are just observances from our ancestors and got passed down to us as to when children roll over, crawl, stand, cruise, walk, talk, etc.
I cannot speak for all the other milestones. But I know that most of the cognitive milestones for children ages 3-5 are based on research studies. I can speak a little bit on this as I’ve done some research on it myself. To call it a milestone – it’s usually not just a single research based on one professor’s research on 30 children. It’s many studies with the same focus but varying many factors and variables and researchers always make sure they are choosing a culturally diverse sample. If not, then chances are there is someone in another country who is replicating the studies.
“Theory of mind” (the understanding that others have a different and separate mind) is a cognitive development milestone for children age 3-5. Research studies on “theory of mind” and its related concepts of “false beliefs” have been done in more than 100 studies. There are many graduate students who are still studying and doing research on this very concept. Maybe one day someone may come up with news breaking research to prove that children acquire theory of mind at the age of two or that autistic children have theory of mind but researchers are not testing them in appropriate ways. (Autistic children are believed to never acquire theory of mind)
I would like to share a research studies on cognitive development that have been on my mind for years. Piaget said that children acquire object permanence - concept of “out of sight is not out of mind” at around the age of 11 months. At around this age, when children see an object and you cover it with a cloth, they will go and reach for the hidden object. But prior to age 11 months, they would not retrieve the object. I’ve tested this with many kids and it’s true. Now, Baillergoen did a research that showed infants at the age of 4 months have object permanence. Baillergeon’s research involved showing videos to the children and looking at the children’s looking time when something change. Some researchers argue that this is not object permanence because one must actually be motivated to uncover the object like those done in Piaget’s research. But 4 months babies do not have the physical abilities to reach for something. (Just on a side note, my son showed evidence of object permanence at the age of 1 month)
The point I am making is that yes, milestones are not absolutely accurate as children may have the cognitive abilities but it’s not possible to test for it. Through the years, researchers are using new ways and techniques to prove that children are smarter than we think they are. But there are always room for more research studies and improvements.