Researchers found that there were cells which contained only maternal or paternal genes in six different parts of the mouse brains which controlled different cognitive functions.
Cells which were associated with the paternal genes involved functions such as sex, food, and aggression and were found in the limbic system. However, researchers did not find any paternal cells in the cerebral cortex where the majority of advanced cognitive functions such as thinking, reasoning, thought, language and planning take place.
Source: Tech Explorist
One could argue that humans and mice are very different and to prove that the same theory applies to people, researchers in Glasgow took a more human approach to exploring intelligence. They found that the theories that they derived from the mice experiment actually apply in reality when they interviewed over 12,686 young people between the ages of 14 and 22 every year from 1994.
The team still concluded that the best predictor of intelligence was the IQ of the mother.
Research also makes it clear that genetics are not the only determinant of intelligence.
Researchers from the University of Washington found that a secure and emotional bond between a mother and child was extremely crucial for growth in some parts of the brain. They analyzed two groups over a period of seven years and found that children who were supported emotionally and had their intellectual/ developmental requirements filled had a 10% larger hippocampus as compared to those whose mothers were emotionally distant.
It is about 40-60% which is hereditary and the rest is up to the environment and nurture but it is safe to conclude that we owe our mothers a lot cause they are the reason we are intelligent.