The Lothian Birth Cohort 1936 sample is in a uniquely good position to provide relevant data on social class mobility patterns over most of the last century. These participants, with known ultimate social class attainment, took a validated mental test in the Scottish Mental Survey of 1947 and were followed up at approximately age 70. Then, besides…

Three papers--comments, a reply to comments, and a rejoinder--discussing a conclusion about the nature of general intelligence based on the size loadings of a psychomotor test of discrimination reaction time are presented. The use of Spearman's "g" is the center of the controversy. (TJH)