This book adapts Rasch’s approach for studying growth to intellectual variables. In Rasch's approach, the natural origin is arbitrary, and it is necessary to construct measurements in a constant unit over the relevant range of the variable. The book illustrates the application of the approach with five variables, one involving the Stanford-Binet test of general intelligence, and two involving proficiencies in reading comprehension and mathematics. The book discusses how it is not immediately obvious that deceleration on a quantitative scale should also hold for the growth in intellectual variables. It goes on to show that this is indeed the case with all five variables analysed, and considers some implications of this feature for understanding intellectual development, in particular, the centrality of the growth trajectory set in early life.weiterlesen