"That disposition, which is so strong in children, still continues with us, of catching involuntarily the general air, and manner, of those with whom we are most conversant; with this difference only, that a young mind is naturally pliable and imitative; but in a more advanced state it grows rigid, and must be warmed and softened, before it will receive a deep impression."
— Reynolds, Joshua (1723-1792)
Text from A Discourse Delivered to the Students of the Royal Academy, on the Distribution of the Prizes, Dec. the 10th, 1774. By the President. (London: Printed for Thomas Davies, 1775). <Link to ECCO>
See also Sir Joshua Reynolds, Seven Discourses Delivered in the Royal Academy by the President (London: T. Cadell, 1778). <Link to Google Books>
Also reading at PGDP.