Lucy was observed lying; something that was once considered uniquely human, because it is evidence of a sense of self. In this sign-language conversation, Fouts asks Lucy about a pile of chimpanzee feces on the floor:
Fouts: WHAT THAT?
Lucy: WHAT THAT?
Fouts: YOU KNOW. WHAT THAT?
Lucy: DIRTY DIRTY.
Fouts: WHOSE DIRTY DIRTY?
Lucy: SUE (a reference to Sue Savage-Rumbaugh, a graduate student of Fouts).
Fouts: IT NOT SUE. WHOSE THAT?
Fouts: NO! NOT MINE. WHOSE?
Lucy: LUCY DIRTY DIRTY. SORRY LUCY.
More details... >http://en.wikipedia.org/wiki/Lucy_Temerlin