Source : Webster's Revised Unabridged Dictionary (1913)

Retentiveness \Re*ten"tive*ness\, n.
   The quality of being retentive.

Source : WordNet®

retentiveness
     n 1: the power of retaining and recalling past experience; "he
          had a good memory when he was younger" [syn: {memory}, {retention}]
     2: the property of retaining possessions that have been
        acquired
     3: the power of retaining liquid; "moisture retentivity of
        soil" [syn: {retentivity}, {retention}]