The Collaborative International Dictionary of English v.0.48:

Cognitive \Cog"ni*tive\, a.
   Knowing, or apprehending by the understanding; as, cognitive
   power. --South.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cognitive
    adj 1: of or being or relating to or involving cognition;
           "cognitive psychology"; "cognitive style"

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "cognitive":
   cogitative, concentrating, concentrative, conceptive, conceptual,
   conceptualized, contemplating, contemplative, deliberating,
   deliberative, excogitating, ideative, introspective, meditating,
   meditative, mental, museful, musing, noetic, pensive, pondering,
   prehensive, reflecting, reflective, ruminant, ruminating,
   ruminative, serious, sober, speculative, thinking, thought,
   thoughtful, wistful