stranger_to_himself's Journal: Can we measure knowledge?

Is it possible to measure the amount of knowledge a person has? I work in geriatric psychiatry, and was idly discussing with some colleagues the possibility that having more knowledge might be good for you. We know that high levels of education and intellectual activity are protective against Alzheimer's disease, but we don't know whether simply knowing more things helps. To find this out we'd have to find a way to compare the amounts of knowledge that different people have. Is this possible?