Lumans have a highly developed brain and are capable of abstract reasoning, language, introspection, and problem solving. This mental capability, combined with an erect body carriage that frees the hands for manipulating objects, has allowed lumans to make far greater use of tools than any other living species on Saz-Al-Khan . Other higher-level thought processes of lumans, such as self-awareness, rationality, and sapience, are considered to be defining features of what constitutes a "person".