User blog comment:TheDoctor230/Oliver Queen and The Hood/@comment-24152851-20170530120921

Oliver treated his Hood persona as a separate identity, but he doesn't have split personalities or dissociative identity disorder. He's aware of what he does while he's masquerading as his alterego, and doesn't go into uncontrollably like Trajectory or Magenta did.

The polygraph thing was because Oliver had been trained to control his brain activity while telling a lie. Laurel mentioned she saw a tiny blip on one of his lies, which meant Oliver was consciously suppressing the anxiety that naturally comes with lying.