What do psychiatrists say about the first six years of a child's life?

Les teaches from the quote that if you give me a young lad until he is six, he's a Catholic forever, then explains that psychiatrists now tell us what a child puts together in the first six years becomes the biggest influence for the rest of life. He applies this to Moses: during the five years Moses nursed on his mother's breast, his parents, people of faith, revealed that the God of Abraham, Isaac, and Jacob would someday take Israel out of Egypt and put them back in Canaan. By age five Moses had that locked in, and despite 35 years under pagan, idolatrous, sumptuous Pharaoh's lifestyle, Moses never forgot, even if he did not respond for a long time. Les also reminds distraught parents of wayward teenagers or twenty-year-olds that Proverbs says train up a child in the way he should go; it does not say he will always stay with it, but when he is old he will not depart from it.