I suspect when God said He would make man in His own image, part of what that meant was—He was making man to think for himself. This happens to be one of those ideas that cannot be verified by pointing directly to a Scripture which clarifies the point. Probably the closest thing which comes to mind is in Isaiah 1:18 where God says through the prophet, come let us reason together.
In my mind this means He had already intentionally made us intelligent. He gave us reason and expected us to use that reason in responsible ways. This is relevant because in order for our actions to be fairly judged they have to be of our own choices, formed by our own decision making processes.
In this way intelligence is the beginning point of personhood, but also the foundation of moral responsibility.