Imagine that we knew everyone’s height and computed the correlation between the heights of fathers and sons. We would find a strong but imperfect relationship, a correlation of about 0.5, as captured by the line running through the data points in the chart below. It tells us that when the father is six feet, we should make a compromise prediction based on both the father’s height and the population average. Our best guess for the son is five feet ten. The son’s height has regressed toward the mean by two inches, halfway between the population average and the father’s height.
So for someone above or below average, we should assume their kids will move closer to the mean even if the attribute is genetically heritable
