Already in the 1950s, researchers: Olds and Milner 1954; Olds 1956 is a popular version.

Studies showed that an important part: There have been many studies of positive affective reactions and of addictions. See, eg, Bozarth 1994; Fiorino, Coury, and Phillips 1997; Berridge 2003; and Wise 1998. A popular-science account is Nestler and Malenka 2004, and very accessible popular books on the experience of pleasure are Linden 2011 and Bloom 2010.

Neuroscientist and author Robert Burton suggested specifically: Burton 2008, pp. 99–100, and p. 218.

is not associated with neural activity: Motivated reasoning implies an emotion regulation. The studies suggest that motivated reasoning is qualitatively different from reasoning when people do not have a strong emotional stake in the results. An extensive review on motivated reasoning is Kunda 1990. The involvement of emotion in decision making is discussed, eg, in Bechara, Damasio, and Damasio 2000. A popular account is Coleman 1995. Westen et al. 2006 present the fMRI studies.

“The concordance of results”: King 1893.