The Collaborative International Dictionary of English v.0.48:

Sociability \So`cia*bil"i*ty\, n.[Cf. F. sociabilit['e].]
   The quality of being sociable; sociableness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sociability
    n 1: the relative tendency or disposition to be sociable or
         associate with one's fellows [syn: sociability,
         sociableness] [ant: unsociability, unsociableness]