Though humans certainly have unique mental capabilities, this fact is irrelevant when trying to distinguish humans from animals. After all, some animals have different brain functions than others, but that does not necessarily set them apart as different and distinct from all other animals.
For example, dolphins can sleep with one hemisphere of their brain at a time, and gold-winged warblers can predict storms days in advance, but no one argues that their unique mental capabilities make these animals fundamentally different from all other animals. Furthermore, no one would claim that their abilities make them smarter, stronger, or better than other animals. It would be illogical to make this same assertion for humans.