At the time of the study, doubts were widespread about the accuracy of eugenicists' mental testing procedures and their simplistic application of the Mendelian model. At the same time, psychiatrists were becoming ascendant over psychometricians as authorities on problem people. The study focused on an Irish family known as the Dacks who arrived in the coal mining region of Pennsylvania about 1815. Their main problem was not gross feeble-mindedness but rather deficiencies in control, ambition, and higher reasoning ability, along with instability in marriage relationships and residence. Descriptions indicate marked differences in the extent to which male and female Dacks suffered from the family affliction. Twenty Dack men and 45 Dack women exhibited lack of emotional control; female Dacks are especially criticized for emotionally uncontrolled behaviors such as shrewdness. The gender discrepancy in lack of emotional control is further strengthened by the tendency to hold Dack women responsible for spouse abuse. The author concludes that a quick temper is inherited as a Mendelian dominant, since the trait did not skip a generation in the Dack family. Dack degeneracy is attributed to two hereditary factors, lack of inhibitive control and lack of mental ability. 1 figure.