“…The body of research examining sleep arrangements, sleep disruption, and child outcomes is growing (for comprehensive reviews, see Goldberg & Keller, 2007;Middlemiss, 2004), but it is complicated by definitional issues and inconsistent terminology. Although solitary sleepers have been consistently defined as infants who sleep alone in their own room (Ball, 2003;Javo, Ronning, & Heyerdahl, 2004;Keller & Goldberg, 2004;Rothrauff, Middlemiss, & Jacobson, 2004), shared sleep can exist along a wide spectrum in terms of duration, degree of proximity, and degree of physical contact between parent and infant (Goldberg & Keller, 2007;McKenna & Volpe, 2007).…”