This study tried to control for all the confounding factors, so it looked at children who were equally intelligent and from the same social-class background, so it seemed as if it was the reading which really helped those children go on and score better on those school tests later in their lives.
Este estudo tentou controlar os fatores de confusão, e observou crianças com o mesmo nível de inteligência e do mesmo contexto social, para demonstrar que a leitura realmente ajudava as crianças a ter melhores resultados em testes escolares posteriores.