As for the precise issue in question, I’m not sure that the fact that all subjects held the position they did is a sign that they were outside the norm. (The position they held may *be* the prevailing consensus, although the report does not say precisely what they were asked to agree to, or what the content of the pro and con articles was.) The reason the group was homogenous for that opinion was that they systematically excluded people who held the other opinion, in order to be sure that everyone’s initial opinion was the opposite of the literature they were going to read.

I presume it’s immaterial whether the subjects’ initial position is pro-choice on voluntary euthanasia or is anti-choice on that issue – the point is that they’re being asked to change their positions. I gather also that this euthanasia questionnaire has become something of a standard test instrument now, because it was used in some early research on opinion formation and so now is used by all follow-on studies for the sake of intercomparability. (An interesting example of how minor historical events can shape an entire area of research. It would be interesting to see if the results of studies like these are affected in any way by societal attitudinal shifts toward the test issue, or by whether the issue represents the status quo of social policy and law, or is counter to the law at the time of the test.)

Also, if the participants were selected for having a particular initial view and also can be expected to have not deeply considered the question, then there may have been, quite regardless of the changing effects of caffeine, a tendedency to revert toward the norm, that is, for their average opinion to become more moderate as it became more well-informed.

In total, it seems that the whole study means nothing at all beyond the initial effect of early increased retension, which is not news to anybody.