I am trying to find an article about child development. Preferably cognitive development in early childhood.
A good place to look for this would be the PsycARTICLES/PsycINFO database. There are links to this on the Find Articles page and the Behavioral Sciences page.
Once you have the database open, you could put each of the two parts of your topic into the search box, surrounding each part with quotation marks: "cognitive development" "early childhood"
I found hundreds of articles that in some way discuss your topic.