Young male albino rats yawn significantly more than females or castrated males when injected with physostigmine (0.10 mg/kg). Treatment with testosterone (100 micrograms daily) during seven days restores cholinomimetically induced yawning in castrated males, and increases yawning in normal and androgenized females. Treatment with estradiol (200 micrograms daily) during one week does not modify ...

Attempts were made in three experiments to induce human subjects to yawn reliably in the laboratory. In subjects who believed they were not observed, reading about yawning did increase their frequency of yawning, compared to reading about scratching or day dreaming. In the second experiment, performing a spontaneous yawn decreased skin conductance, but "faked" yawns did not have this effect. In...

Contagious yawning-the urge to yawn when thinking about, listening to, or viewing yawning-is a well-documented phenomenon in humans and animals. The reduced yawn contagion observed in the autistic population suggested that it might be empathy related; however, it is unknown whether such a connection applies to nonclinical populations. We examined influences from both empathy (i.e., autistic tra...

Yawning can be regarded as a prototype of stereotypical behaviors that has been recycled through evolution for different purposes. These purposes are combined with the increasing complexity of the central nervous system during evolution, and correlated with the richness of social interactions. In this chapter, past and current hypotheses concerning the generation and usefulness of yawning are d...

Psychological, clinical and neurobiological findings endorse that empathic abilities are more developed in women than in men. Because there is growing evidence that yawn contagion is an empathy-based phenomenon, we expect that the female bias in the empathic abilities reflects on a gender skew in the responsiveness to others' yawns. We verified this assumption by applying a linear model on a da...

The thermoregulatory theory of yawning posits that yawns function to cool the brain in part due to counter-current heat exchange with the deep inhalation of ambient air. Consequently, yawning should be constrained to an optimal thermal zone or range of temperature, i.e., a thermal window, in which we should expect a lower frequency at extreme temperatures. Previous research shows that yawn freq...

Low risk, premature infants between 30 to 35 weeks post-conceptual age (PCA) residing in an neonatal intensive care unit environment were observed in the home incubator for spontaneous yawning from 2400 to 0500 hr. Videorecordings were analyzed for the behavioral states of quiet sleep (QS), active sleep (AS), wake (W), and drowse (D) in 3-min epochs as well as the contextual behaviors before an...