Charisma Inhibits Higher Brain Function In Believers.

Unfortunately this study only covered religious subjects, but its lessons can be applied pretty much anywhere. “Experts” are trotted out every night on news programs, to justify the most heinous of activities, or just to instill fear in the population. Politicians and other rulers practice being charismatic because it saves them having to be truthful. The voluntary and NGO sector is full of “conference dragons”, and so on.

The study found that a religious person, anticipating a person who has a reputation as a charismatic literally shuts down his highest brain functions in the charismatic’s presence. That doesn’t happen in the brains of non-believers.

An article on OpEdNews.com does some interesting speculation about this (archived as pdf: Power_of_Charisma) but again is limited by only looking at religious matters. The full study is available at intl-scan.oxfordjournals.org and pdf is archived here:
Soc Cogn Affect Neurosci-2011-Schjoedt-119-27

See also:  The science of charismatic voices on phys.org for some studies using politicians’ speeches.
(archived as pdf: phys.org-The_science_of_charismatic_voices )

Edit, 22 Nov 2014: Found a similar study that focuses on experts rather than religion:

Expert Financial Advice Neurobiologically Offloads Financial Decision-Making under Risk