'Wild West' mentality lingers in modern populations of US mountain regions. Scientists looked at links between the personality profiles of over 3.3m US residents and the 'topography' of 37,227 ZIP codes. Distinct psychological mix associated with mountain populations is consistent with theory that harsh frontiers attracted certain personalities. Researchers argue this may be residual from US frontier expansion during the 19th century, as personality pattern is strongest in the West. Source 5b.