Visual awareness increases during months 4 through 7, and babies begin to notice new aspects of their environment. During this time, mirrors become a source of fascination for most babies. Most babies will be interested in the reflected images that result when they move their legs or reach for things. They are beginning to connect mirror images with their own bodies.
Shelov, S. P. (Editor-in-Chief). (2004). Caring for Your Baby and Young Child: Birth to Age 5. The American Association of Pediatrics. Revised edition. New York: Bantam Books.