Charlie Geilsberg POV
[The kid has changed; now he tells lies with such conviction that it seems to be the truth.]
Charlie is baffled by Eren's transformation from the suppressed child he has always been to a new person who doesn't suppress by anyone anymore; Eren is behaving in a manner Charlie cannot comprehend.
[Has he come under someone's control? Naa, he is behaving differently, but inherently he is still the same old him. Perhaps this is what people call puberty.]
Since rankers perceive the environment differently than regular people, perceive time as moving more slowly, and have a larger capacity for information processing in their brains, rakers can process more information than regular people even when they are completely intoxicated. For a first-peak Renker, this is a piece of child's play to notice changes inside people.