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Common Ground from WikiPedia:

Finding common ground is a technique for facilitating interpersonal relationships. In order to find common ground between parties, participants must search for signals of recognition, which are often subtle and cause for misunderstanding. Generally, smiles, bland faces, or frowns can be the positive, neutral or negative signals. When verbal communication is possible, the participants can speak and then listen.

Historically, the commons in many communities were a place which was available to everyone, such as the village pump, or the sidewalk of a road. Thus even for those far from home, the sight of someone familiar only from the commons might be comforting to a homesick or lonely traveller. This effect can be seen in many kinship groups. One measure for interpersonal relationships is warmth. Thus discovery of common ground is commonly cause for comfort and additional happiness among the participants, and is one step on the way to respect or perhaps friendship.

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