Temperature-Dependent Variation in Self-Reported Contagious Yawning

Abstract

The thermoregulatory theory posits that yawns function to cool the brain in part due to counter-current heat exchange with the deep inhalation of ambient air. In support of this theory, previous cross-cultural research on humans has shown that self-reported contagious yawning frequency varies between seasons with distinct ambient temperature ranges. However, it remains possible that differences in yawning across seasons are a result of physiological circadian changes across the year rather than variation in ambient temperature. In an attempt to address this question, here we discuss the results of a study investigating the variation in the frequency of self-reported contagious yawning within a restricted range of a single season in one geographic location. A total of 142 pedestrians were recruited outdoors during an 18-day period over the summer in an equatorial monsoon climate in southern Florida, USA. Consistent with the thermoregulatory theory of yawning, results showed that self-reported contagious yawning frequency varied predictably across temperature gradients. This was true after statistically controlling for relative humidity, time of day, time spent outside, testing day, age of participant, and amount of sleep the night before. These findings provide further evidence suggesting a brain cooling function to yawning.

Yawning Detection Sensitivity and Yawning Contagion

“…Moreover, a sexually immature group like children is not a good sample group for studying gender differences (Norscia, Demuru, & Palagi, 2016b). Second, 5 of the 15 studies did not include a baseline condition to control for spontaneous yawning ( Bartholomew & Cirulli, 2014 ; Eldakar et al., 2015 ; Gallup, Church, Miller, Risko, & Kingstone, 2016 ; Gallup & Eldakar, 2011 ; Massen, Dusc, Eldakar, & Gallup, 2014 ). A control condition (i.e., in our case, a smiling video) or a baseline measurement (e.g., spontaneous yawning in Norscia et al., 2016a ) offers an assurance that the recorded yawning was not predominantly spontaneous yawning, which is known to have no gender difference ( Schino & Aureli, 1989 ), but contagious yawning which was our central research interest.…”

“…It is possible that the initial female advantage to yawning susceptibility was counterbalanced by the higher inhibition of yawning behavior in females. Participants in 4 of the 15 studies were aware of experimenters’ observation of their yawning behavior as they viewed the yawning photos directly in front of the experimenter ( Eldakar et al., 2015 ; Gallup & Eldakar, 2011 ; Gallup & Gallup, 2007 ; Massen et al., 2014 ). This makes it possible that the gender difference was absent due to the pressure to inhibit yawning behavior, especially in females, due to the social presence of the experimenters.…”

There is no difference in contagious yawning between men and women

“…[ 18 ] n = 44 a naturalistic video clips objective continuous no effect Eldakar et al. [ 19 ] n = 142 (70) naturalistic static images self-report binary no effect Massen et al. [ 20 ] n = 118 (82) laboratory static images self-report (and objective) b binary no effect Rundle et al.…”

Ambient temperature modulates yawning

“…By sampling pedestrians across divergent seasons and climatic conditions, these studies first demonstrated that contagious yawning (much like the spontaneous form) became less common at temperature extremes. In a follow-up study, 1 which controlled for potential physiological circadian changes that may produce distinct patterns of yawning across different seasons, 142 pedestrians were shown a contagious yawning stimulus while being outside during an 18-day period over the summer in southern Florida, USA. Consistent with the thermal window hypothesis, self-reported contagious yawning was most frequent (60.5%) at moderately warm temperatures, but dropped precipitously (23.8%) as air temperatures approached human body temperature.…”