Demons were intelligent, and their intelligence was not lower than that of humans. However, this was only limited to demons, or rather, demons of the fourth rank and above. Demons of the third rank and below could also be considered wild beasts, and they only had low intelligence.
The spiritual transformation of monsters above the fourth rank was called the light of wisdom, which was why they could compete with humans for the position of the child of the world. The key was to win this battle...
However, after a demon had condensed the light of wisdom, it would possess a normal level of intelligence. The increase in level would no longer have any help to its intelligence level, but would gradually mature as the brain developed. Finally, the development of intelligence would be carried out by knowledge, human feelings, and experience, and they would be no different from a human.