Perhaps the most devastating problem with subjective [survey] questions, however, is the possibility that attitudes may not “exist” in a coherent form. A first indication of such problems is that measured attitudes are quite unstable over time. For example, in two surveys spaced a few months apart, the same subjects were asked about their views on government spending. Amazingly, 55% of the subjects reported different answers. Such low correlations at high frequencies are quite representative.
Part of the problem comes from respondents’ reluctance to admit lack of an attitude. Simply because the surveyor is asking the question, respondents believe that they should have an opinion about it. For example, researchers have shown that large minorities would respond to questions about obscure or even fictitious issues, such as providing opinions on countries that don’t exist. (more; HT Tyler)
I’m not clear on just how far this effect goes, but one lesson is: you have fewer real opinions than you think. If you talk a lot, you probably end up expressing many opinions on many topics. But much, perhaps most, of that you just make up on the fly. You won’t give the same opinion later if the subject comes up again, and your opinion probably won’t effect your non-talk decisions.
So your decisions on charity donations, votes, and who or what to give verbal praise, may be a lot simpler than you think. Your decisions on where to live or work, and who to befriend or marry, may also be simpler. That is, you may consistently make similar decisions, but the reasons you give for them may matter less than you think.
It's fitting that my least favorite writer nailed this point completely:
"But why should you keep your head over your shoulder? Why drag about this corpse of your memory, lest you contradict somewhat you have stated in this or that public place? Suppose you should contradict yourself; what then? It seems to be a rule of wisdom never to rely on your memory alone, scarcely even in acts of pure memory, but to bring the past for judgment into the thousand-eyed present, and live ever in a new day. In your metaphysics you have denied personality to the Deity: yet when the devout motions of the soul come, yield to them heart and life, though they should clothe God with shape and color. Leave your theory, as Joseph his coat in the hand of the harlot, and flee.
A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines. With consistency a great soul has simply nothing to do. He may as well concern himself with his shadow on the wall. Speak what you think now in hard words, and to-morrow speak what to-morrow thinks in hard words again, though it contradict every thing you said to-day."
Emerson, in Self Reliance
Contemplation and critical thinking are what give weight to opinion. Modern life is designed to eliminate both.