The forms and behavioral correlates of yawning are described, and the phylogenetic and ontogenetic aspects of the act are examined with particular attention to its possible functions. Much evidence supports the view that yawning is an important mediator of behavioral arousal levels, a view that is further strengthened by a review of endocrine, neurotransmitter, and pharmacological mechanisms of...

This study is the first to demonstrate that human yawns are possibly contagious to domestic dogs (Canis familiaris). Twenty-nine dogs observed a human yawning or making control mouth movements. Twenty-one dogs yawned when they observed a human yawning, but control mouth movements did not elicit yawning from any of them. The presence of contagious yawning in dogs suggests that this phenomenon is...

Yawning is related to sleep/wake transitions and time of day, probably reflecting the time course of sleepiness. As aging modifies sleep-wake and sleepiness rhythms, we suppose that yawning frequency and its time course vary as a function of age. Thirteen aged healthy subjects (77.15 +/- 4.09 years) and 12 young adults (24.41 +/- 3.31 years) were instructed to keep their habitual sleep schedule...

In this study, the effects of intraperitoneal (ip) injection of physostigmine, subcutaneous (sc) injection of atropine, and intracerebroventricular (icv) injections of histamine, chlorpheniramine (H(1)-receptor antagonist), and ranitidine (H(2)-receptor antagonist) in separate and combined treatments were investigated during yawning in rats. Physostigmine at a dose of 0.25 mg/kg produced the hi...

Numerous theories as to why we yawn have been advanced, but yawning appears to be a complex phenomenon that is difficult to study. The physiology of yawning with its sharp chest inhalation, along with its contagious nature, can be explained by an arousal theory, that is, yawning promotes vigilance and alertness within a group that overrides a drive to sleep. Other theories of yawning, such as b...

Yawn contagion is not restricted to humans and has also been reported for several non-human animal species, including chimpanzees (Pan troglodytes). Contagious yawning may lead to synchronisation of behaviour. However, the function of contagious yawning is relatively understudied. In this study, we investigated the function of contagious yawning by focusing on two types of signal providers: clo...

OBJECTIVE Crocin and safranal, as the major constituents of saffron, have many biological activities. This study investigated the effects of crocin and safranal on yawning response induced by intracerebroventricular (i.c.v.) injection of histamine in rats. MATERIALS AND METHODS In ketamine/xylazine-anesthetized rats, a guide cannula was implanted in the right ventricle of the brain and yawnin...

Recent research suggests that yawning is an adaptive behavior that functions to promote brain thermoregulation among homeotherms. To explore the relationship between brain temperature and yawning we implanted thermocoupled probes in the frontal cortex of rats to measure brain temperature before, during and after yawning. Temperature recordings indicate that yawns and stretches occurred during i...

Yawning continues to pose as a scientist’s conundrum. Evidence is presented of yawning and contagious yawning in a number of different neurological disorders. Explanations are discussed in the context of disparate neurological disorders together with proposals for how these findings may be linked. Thus, greater understanding of yawning and of neurological disorders may be achieved by exploring ...