Because they did an experimental study, with a reversal design, Hart and Risley were able to demonstrate that the number of words mommies and daddies say to their pre-school kids determines their kid's vocabulary size and resulting success in school.

Question

Quizplus · Accepted Answer

Hart and Risley's study was observational, not experimental, meaning they recorded the natural interactions between parents and children without manipulating any variables. They found a correlation between the amount of words spoken to children and their later vocabulary and educational success, but correlation does not imply causation.

Because They Did an Experimental Study, with a Reversal Design