Bernard Cohen, 1963: the press may not be successful much of the time in telling people what to think, but it is stunningly successful in telling them what to think about.

The empirical backing came a decade later (McCombs and Shaw, 1972, the Chapel Hill study). They surveyed undecided voters during the 1968 US election on which issues they considered most important, then content-analysed the news those voters were actually consuming. The rank order matched almost perfectly.

Ive never read those studies. I'm talking merely from my own experience and observations.

Apparently, an incoming stream of information sets a cognitive agenda. Every now and then, one gets a freshly prepared list of things worth having a position on.

One never gets to ask himself:
Why do I really care about X in the first place?

Do I get substantial benefits from thinking about it?
Do I enjoy thinking about it?