“…Even though spontaneous yawning is considered a fixed action pattern, its description is not fixed at all. Spontaneous yawning has been described as consisting of long, deep inspiration, brief peak with apnea (acme) followed by a slow expiration (Walusinski and Deputte, 2004;Guggisberg et al, 2010) sometimes reported as rapid (Baenninger, 1997;Krestel et al, 2018) or shorter (Provine, 2012;Gallup et al, 2016). When integrating the different descriptions of the motor patterns defining a yawning event (Walusinski and Deputte, 2004;Guggisberg et al, 2010;Provine, 2012;Baenninger, 1997), it is possible to claim that it includes active jaw gaping, eye closure, contraction of facial muscles, and passive jaw closure, accompanied by neck stretching and head tilting and, in some cases, by limb and body stretching.…”