Actigrams for each partner of a true (A,B) and randomly paired (D,E) couple for one night using the dyadic rest interval. Binary illustration of concordance presented below actigrams (C,F). Panels C and F represent 89% and 75% sleep-wake concordance, respectively. The gray, upper lines illustrate when the couple is concordant for wake or sleep. The black, lower lines illustrate when the couple is discordant.