“…Infants increase the rate of sucking, for example, as readily when their sucks are followed by their mother's voice (DeCasper & Fifer, 1980;Mills & Melhuish, 1974), a computer-generated speech sound (Eimas, Siqueland, Jusczyk, & Vigorito, 1971;Trehub & Rabinovitch, 1972), music (Butterfield & Siperstein, 1972), a movie (Bower, 1967;Kalnins & Bruner, 1973), colored slides of geometric shapes (Franks & Berg, 1975;Milewski & Siqueland, 1975), the movement of a crib mobile (Little, 1973;Rovee & Rovee, 1969), or termination of white noise (Butterfield & Siperstein, 1972), as when their sucks are followed by a squirt of sugar water (Kobre & Lipsitt, 1972) or milk (Hillman & Bruner, 1972;Sameroff, 1968)! Head-turning is similarly reinforced by a variety of biologically unrelated consequences-a visual pattern (Levinson & Levinson, 1967) or a novel toy (Koch, 1968), a human jack-in-the-box (Bower, 1964), visual access to the mother or a stranger (Koch, 1968), a squirt of milk (Papousek, 1961) or sugar water (Clifton, Siqueland, & Lipsitt, 1972), a nonnutritive nipple (Siqueland, 1968a), or simply by "being correct" (Papousek, 1967).…”