The aliens realize we're not actually conscious. Humans 'think' for 16-18 hours, then need to compact their context window for 6-8 hours where they hallucinate pretty much the whole time, then start over again. No true continuity of experience, just a series of fruit flies sharing a notebook
Alternate ending to "Contact" where Jodie Foster realizes that the aliens' thought processes are discrete instead of continuous, thus they are not intelligent