I looked through the other questions/answers about this movie and I didn't see an answer to a question I had. About halfway through the movie, perhaps a little less than halfway,
Caleb accuses Nathan of designing Ava to be sexually attractive specifically to Caleb. Caleb appears capable of thinking critically about Ava even when he's extremely sexually attracted to her. He also appears familiar with AI programming and should understand that there is a very high probability that Ava is manipulating him/lying to him and is not benign. (He's also portrayed a bit stereotypically as a 26-year-old introvert who would probably be familiar with Isaac Asimov and other science fiction writers.)
Why is Caleb so quick to accept Ava's suggestion that Nathan is a liar and help release her? Why isn't he able to understand the moment he lets her out of the box she might betray him?