Question: What is the mechanism for contagious emotions?
My hypothesis: A mood "resonates" when mechanical motions of one body (e.g. a yawn) initiate corresponding ones in a body perceiving them. This is the same result as explained by "mirror neurons," but here is based on the principle that two coupled, actively-controlled mechanical objects can resonate.
Test: After establishing a protocol for measuring contagious emotions via a high-bandwidth interface like multi-sensory telepresence, progressively dial-down the bandwidth and watch the emotional communication decrease.
Refutation: Show that emotional communication is independent of sensory bandwidth.
(My own experience, and that of my friends, is that the quality of interpersonal connection scales directly with interpersonal bandwidth, with the most intimate being the megabyte-or-so per second of face-to-face contact in a quiet, well-lit place, then decreasing with bandwidth through video calls, landlines, cell phones, emails, and texts, with the very lowest being single-bit "likes" ).