This volume represents one of the University of Iowa Studies in Child Welfare. It is an exceedingly elaborate study, filled with tables, graphs, charts, and equations. It also is well thought out. As Stoddard's foreword says, “These topological studies are not essays for puzzled parents nor are they browsing materials for anyone ‘catching up’ on child research. “Retrogression is distinguished from regression in that the former is not necessarily to a more primitive type of behavior. The varieties of regression are examined, such as regression in behavior without regression of the person, situational and established regression, etc. Regression is examined from the views of variety, organization, activity area, and the realism of behavior. Case studies are given as well as the technique of studying children in free play and frustration situations. It is said that it is important to use psychological rather than physical time units; units of action, episodes of behavior, and total experimental periods.