The Collaborative International Dictionary of English v.0.48:
Sociableness \So"cia*ble*ness\, n. The quality of being sociable. [1913 Webster]WordNet (r) 3.0 (2006):
sociableness n 1: the relative tendency or disposition to be sociable or associate with one's fellows [syn: sociability, sociableness] [ant: unsociability, unsociableness]