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Contagious yawning is hypothesized to be linked to empathy. This hypothesis is supported by studies finding negative relationships between autism and contagious yawning and schizophrenic personality traits and contagious yawning, both conditions believed to involve impairment of empathy. Furthermore, an fMRI study found that areas of the brain associated with viewing social cues are also active during contagious yawning. In addition, a study of chimpanzees found that thirty-three percent (two out of six) of the subjects displayed contagious yawning when presented with a video of chimpanzees yawning. The present study attempted to replicate these results using a larger sample size (N=24). 3D animations of chimpanzee faces, each of which performed four actions—yawning, tooth clack, pant-hoot, and play face—were presented to twelve mutually exclusive pairs of chimpanzees. We compared the degree of yawning displayed during the yawning animations to the degree of yawning displayed during the other animations to determine whether the chimpanzees displayed contagious yawning. We found that the chimpanzees yawned at a greater rate while watching videos of yawning than while watching videos of non-yawn mouth movements, supporting our hypothesis that chimpanzees display contagious yawning. We also recorded attention to the videos, allowing us to study the relationship between attention and contagious yawning. We found that attention to the video did not differ significantly across sessions, and, therefore, that there was no evidence of habituation. In addition, we found that there was no consistent correlation between attention and yawning for either the experimental or control conditions. Our results and large sample size allowed us to confirm that chimpanzees display contagious yawning and conclude that 3D rendered animations can stimulate contagious yawning, and possibly other responses, in chimpanzees. However, our measure of attention was not an adequate predictor of contagious yawning.
Perception Action Model: contagious yawning is linked to other contagious behaviors and emotions (Preston and de Waal, 2002)
Relationship between contagious yawning and empathy
An fMRI study (Schurmann et al, 2005) found viewing videos of yawning activated brain areas associated with viewing social cues
Autistic children display less contagious yawning than controls (Senju et al, 2007)
College students scoring higher on schizophrenic personality traits display less contagious yawning than those scoring lower
Evidence of contagious yawning in non-human primates
Stumptail macaques yawn more while watching yawning videos than while watching control videos (Paukner and Anderson, 2005)
Chimpanzees exhibited a greater degree of yawning while viewing yawning videos than while viewing control videos (N=6) (Anderson et al, 2004)
Purpose of the Study
Expand upon Anderson study by increasing sample size (N=24)
Determine whether attention to the video correlates with contagious yawning
Use the measure of attention to evaluate alternative hypotheses suggesting that factors other than the yawn video resulted in any differences in yawn rate
Determine whether the chimpanzees become habituated to the videos and whether habituation affects the degree of contagious yawning across sessions
Twelve mutually exclusive chimpanzee pairs assigned based upon compatibility (N=24)
3D rendered chimpanzee faces animated to perform four actions: yawn, tooth clack, pant-hoot, and play face
Rendered faces from three angles: front, right, and left
Two Videos
Yawn: 90 yawn clips, 15 min
Control: 90 other open mouth movements, 15 min
15 minutes of video followed by 5 minutes of observation to monitor build-up effect
Two yawning and two control sessions counterbalanced across subjects
Sessions video-taped
Each session scored for yawning and attention from video-tape
Attention scored on a range of 0 to 2 in 5-second scan samples
0 – Unable to see video
1 – May have been able to see, but no focused attention
2 – Full Attention
Tested for outliers
One chimpanzee’s yawn count was 1.5 times the interquartile range away from the median
Chimpanzee’s yawn count was four standard deviations above the mean
Dropped this chimpanzee from all data analysis
For the purposes of all reported statistics N=23
Found more yawning in yawn sessions than in control sessions
Attention to video: yawning vs. control conditions – Wilcoxon
Additive focused attention (attention = 2) to the video did not differ significantly between conditions: T23 = 101.00, p > .05
Additive possible attention + focused attention (attention = 1+2) to the video differed significantly between conditions: T22 = 36.50, p < .01
Additive Attention of 1+2 for yawning conditions = 5387
Additive Attention of 1+2 for control conditions = 4625
Significant habituation over time within sessions – Spearman correlation
Average attention of 2 across one minute increments: R2 = -.858, p < .001
Average attention of 1+2 across one minute increments: R2 = -.692, p = .004
No consistent habituation across the four sessions – Friedman Test
Attention of 2 across all trials: Χ2 = 6.569, p = .087
Attention of 12 across all trials: Χ2 = 6.118, p = .106
No consistent correlation between attention and yawning across individuals – Spearman
No consistent correlation between attention and yawning across time within sessions – Spearman
Chimpanzees display contagious yawning
3D rendered animations can stimulate contagious yawning, and possibly other contagious behaviors, in chimpanzees
Focused attention not significantly different between yawn and control conditions
For measure of possible attention + focused attention chimpanzees paid more attention to the yawn video, but it did not correlate with rate of yawning – Control video was an adequate control
Our measure of attention was not an adequate predictor of contagious yawning – Short periods of attention may stimulate long yawning bouts
Possible Future Directions
Add a measure of attention for focused attention at a longer distance
Precise measure of attention rather than sampled measure of attention
Analyze data of yawning individuals separately
Link performance in this study to performance in studies of other behaviors also associated with empathy
Acknowledgements: This material is based upon work supported by the Howard Hughes Medical Institute under Grant No. 52005873 and Yerkes base grant NIH No. RR-00165.
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