Baby Introverts?

Since my baby was born, I've been reading baby books of course, and The Wonder Weeks (van de Rijt and Plooij, 2013) had this to say in their chapter on week 12 of infant development: "Some babies are very aware of the world around them, and they prefer looking, listening, and experiencing sensations to being physically active themselves" (96). Hm, sounds like baby HSPs (Highly Sensitive Persons, to use Elaine Aaron's term) to me! But the bias is present against even baby introverts: "Most of the time, professionals, as well as friends and family, assess a baby's development by looking at the physical milestones, such as grasping, rolling over, crawling, sitting, standing, and walking. This can give a one-sided view of progress as it makes the 'watch-listen-feel' baby seem slower" (97).