Personal space preferences distances inside which a person is uncomfortable when someone encroaches can vary between people of different ethnicity. Certain vocal intonation speech variations if body language is extended to cover everything but the spoken words also fall within this environmentally determined category.
Other alerting signals include raising the hand, taking a breath, moving upwards and forwards in their seat, etc. The human body and our instinctive reactions have evolved to an amazingly clever degree, which many of us ignore or take for granted, and which we can all learn how to recognize more clearly if we try.
It became properly established during the early s and increasingly extends to human behaviour and social organization. A study conducted by researchers at Liverpool and Stirling Universities recruited women and 64 men, asking one group to assess images of the opposite sex with digitally added facial scars while another group viewed blemish-free mug shots.
Body Language is also referred to as 'non-verbal communications', and less commonly 'non-vocal communications'. The term synchronized is arguably a more accurate technical term because mirroring implies visual signals only, when the principles of matching body language extend to audible signals also - notably speech pace, pitch, tone, etc.
That is what the AncestryDNA test had picked up.