ABSTRACT
Research reveals that only warm-blooded animals-only mammals and birdsexhibit a period of sleep manifesting rapid eye movement or REM (Capellini, 2012; Hartmann, Bernstein, & Wilson, 1968; Low, Shank, Sejnowski, & Margoliash, 2008; Lyamin, Shpak, Nazarenko, & Mukhametov, 2002; McNamara, 2004; Nicol, Andersen, Phillips, & Berger, 2000; Rattenborg, 2006; Rattenborg, Amlaner, & Lima, 2000; J. M. Siegel, 2008; Siegel et al., 1999). And as classic studies by Aserinsky and Kleitman (1955) and Dement and Kleitman (1957) demonstrated, this period of REM sleep in humans is cyclical, normally recurring every 90-120 minutes throughout the night, and is associated with visual dreams that are usually remembered by the dreamer upon being awakened and queried shortly after REM sleep ends. The question of interest to us is whether such periods of REM sleep in other mammals and in birds are also indicative of dreaming.
