Yawning is contagious in humans as well as other mammals. It is an topic of research. I am posting an abstract of a recent paper from a scientific journal Animal cognition, for a better concept.
Anim Cogn. 2013 Aug 28. [Epub ahead of print]
Familiarity-connected or stress-based contagious yawning in domestic dogs (Canis familiaris)? Some additional data.
Silva K, Bessa J, de Sousa L.
Departamento de Ciências do Comportamento, Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Largo Prof. Abel Salazar, 2, 4099-003, Porto, Portugal
The present short note aimed at further exploring data from a recent study showing socially modulated auditory contagious yawning in domestic dogs (Canis familiaris). Two independent observers further extended the analysis of all video recordings made in the previous study and coded both the number of yawns performed by the dogs and the frequencies or durations of stress-related behaviors exhibited throughout the presentation of familiar and unfamiliar yawns. By showing no significant difference between conditions in the frequencies or durations of the coded behaviors, nor any association between the number of yawns and the frequencies or durations of stress-related behaviors, results raised doubt on the stress-induced yawn hypothesis, thus supporting social modulation. The exact mechanism underlying contagious yawning, however, needs further research.