Daniel Kruger found widespread use of mobile phones during face-to-face interactions among young adults — use that tended to increase among all group members when one companion used their phone. “There is thus is a pattern of contagion” in phone use, says Kruger, which may result simply from imitation, but could signal feelings of social exclusion, especially in small groups. “If one person in a pair engages in an external conversation through their phone, his or her companion may feel excluded. That companion then might be compelled to connect with others externally so as not to feel left out.”

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