Intelligence determines how far and how accurately one can model the future inside their brain. It is synonymous with pattern recognition. With low intelligence one can only superficially understand how things in their environment function. Midwits don't have powerful enough pattern recognition skills, so they have to defer to the opinions of experts in their day to day lives, because the results from their thinking yield too incomplete pictures of the future to be useful. Standard intelligent test is testing individual's ability to see what comes next by interpreting abstract data. Famously some African tribes don't have the abstract idea of future, because people with low intelligences can't see at all in the future, and can only react to their immediate surroundings.
