Hello Rushingrocks!
The study says that children who grown up in homes which are in better conditions of health, incomes, environment and parents, their IQ is higher than in children who grown up in poor conditions.
Apart the genetic material which directly influence the IQ of each person, the closer factors like their home are important in the development.
The study suggests that children who lives a life with more opportunities than others, will have more chances of succeed than children from poorest homes.