“…Learning models have been studied in relation to singular points (Amari, Park, & Ozeki, 2006;Wei, Zhang, Cousseau, Ozeki, & Amari, 2008;Cousseaeu, Ozeki, & Amari, 2008;Satoh & Nakano, 2013;Nitta, 2013a). For example, learning models with hierarchical structures or a symmetric property on exchange of weights, such as hierarchical neural networks and mixture models, mostly have singular points.…”