When we try to understand thoughts generate , Simple perceptions of reality is not capable of generating thoughts, effort to understand is the cause for it.
Normal people can have one thought at a time while genius is capable of having multiple thoughts about a single thought at a time.
Expressive genius is capable of expressing multiple thoughts with a single thought at a time, while a normal one would express one thought about a thought at a time.
Evolution will give us the capability to express abstract thoughts rather than thoughts about a thought some of us who are another kind of genius know how to do it using coding languages already but it gets difficult while using commonly known languages or in day to day interactions.