The young man has certain considerations: The princess does love him, but she has seen him talking with a fair maiden and has become jealous as a result. And, she does have barbarism coursing through her blood. In addition, the princess knows the young woman who stands behind one door, a young coutier who has cast admiring looks at the young man many a time.
The girl was lovely, but she had dared to raise her eyes to the loved one of the princess; and, with all the intensity of the savage blood transmitted to her through long lines of wholly barbaric ancestors, she hated the woman sho bluched and trembled behind that silent door.
Yet, even though the young man knows that the princess is aware of who is behind the doors, when the princess indicates the door to the right, it is this same door that the young man chooses, also. He chooses the door to the right, the same that she has chosen because, he believes, she figures that he will think she is trying to trick him since she is jealous, so he will then choose the left door where lies the tiger.
When he chooses the right door, it should, then, be the one containing the fair maiden.