On Measuring Worldviews.
A sobering thought from Daniel Gilbert's excellent Stumbling On Happiness.
"It is extremely difficult to measure an individual's happiness and feel completely confident in the validity and reliability of that measurement. People may not know how they feel, or remember how they felt, and even if they do, scientists can never know exactly how their experience maps onto their description of their experience, and hence they cannot precisely know how to interpret people's claims. All of this suggests that the scientific study of subjective experience is bound to be tough going."
So measure what happens, not what people say will happen and keep on measuring.