title: Yawning, acute stressors, and arousal reduction in Nazca booby adults and nestlings.
abstract: Yawning is a familiar and phylogenetically widespread phenomenon, but no consensus exists regarding its functional significance. We tested the hypothesis that yawning communicates to others a transition from a state of physiological and/or psychological arousal (for example, due to action of a stressor) to a more relaxed state. This arousal reduction hypothesis predicts little yawning during arousal and more yawning (above baseline) during and after down-regulation of arousal. Experimental capture-restraint tests with wild adult Nazca boobies (Sula granti), a seabird, increased yawning frequency after release from restraint, but yawning was almost absent during tests. Natural maltreatment by non-parental adults also increased yawning by nestlings, but only after the maltreatment ended and the adult left. CORT (corticosterone) was a logical a priori element of the stress response affecting the stressor-yawning relationship under the arousal reduction hypothesis, and cannot be excluded as such for adults in capture-restraint tests but is apparently unimportant for nestlings being maltreated by adults. The arousal reduction hypothesis unites formerly disparate results on yawning: its socially contagious nature in some taxa, its clear pharmacological connection to the stress response, and its temporal linkage to transitions in arousal between consciousness and sleep.
authors.affiliation: Department of Biology, Wake Forest University, Winston-Salem NC 27109 USA.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Liang
authors.affiliation: Department of Biology, Wake Forest University, Winston-Salem NC 27109 USA.
authors.forename: Jacquelyn K
authors.initials: JK
authors.lastname: Grace
authors.affiliation: Department of Biology, Wake Forest University, Winston-Salem NC 27109 USA.
authors.forename: Emily M
authors.initials: EM
authors.lastname: Tompkins
authors.affiliation: Department of Biology, Wake Forest University, Winston-Salem NC 27109 USA. Electronic address: da@wfu.edu.
authors.forename: David J
authors.initials: DJ
authors.lastname: Anderson
mesh_terms: D000818:Animals; D001143:Arousal / Q000502:physiology*; D001717:Birds; D003345:Corticosterone / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D008297:Male; D009425:Nesting Behavior / Q000502:physiology*; D011930:Reaction Time; D012149:Restraint, Physical / Q000523:psychology*; D018709:Statistics, Nonparametric; D013315:Stress, Psychological / Q000097:blood / Q000503:physiopathology*; D014743:Videotape Recording; D015000:Yawning / Q000502:physiology*
chemical_list: D003345:Corticosterone
keywords: Capture-restraint stress test; HPA axis; Non-parental adult visitors