(a) Selective breeding for high versus normal anxiety-like behavior levels (HAB/NAB) was performed for over > 40 generations starting with outbred CD-1 mice7. Selection was based on results of the Elevated Plus-Maze test (% time in the open arm). After the animals of each respective genotype were weaned, they were mixed into groups of three NABs and one HAB each. (b) The power of the identity domain (ID) scores to detect genotype was tested directly using the area under the receiver operating characteristic curve of a model predicting genotype based on IDs 1-4. The area under the curve of this model was compared against a distribution created based on 200 trials with shuffled ID scores.