Cognitive Relativity

"Measurement" is any procedure used to find out how much of some- thing a person has. We measure your height by counting the number of inches from the bottom of your feet to the top of your head. This is an absolute measure because we know what zero length means and we have a fixed unit like the inch to use in measuring length. To say that you are six feet tall means that you stretch out 72 inches from bottom to top. We could be interested in a relative measure of height. How tall are you compared with others of your age and sex? How tall are you relative to the other people in your family or in your social group? Relative measures compare you with other people; six feet would be tall in a college sorority, but it would be short on a men's basket- ball team. In contrast to height and other physical properties that can be measured both absolutely and relatively, there are no absolute measures of cognitive attributes.

Principle of Cognitive Relativity
All measurements of cognitive factors are relative
(i.e., one can only measure individual differences.)

To illustrate the principle with intelligence, we don't know what zero intelligence would mean and we don't have units of intelligence to measure how many you have. The only way to measure intelligence is relative to other people. To say that your IQ is 100 means only that you have average intelligence; the higher your IQ, the smaller the percentage of people who are as intelligent as you are. Knowledge is a cognitive factor. Accordingly, a test can only measure how much you know about a subject relative to how much other comparable students know. Students sometimes ask whether an exam is graded "on a curve," and the answer is that exams are always graded on a relative basis. Experienced teachers write exams at the level that is appropriate for a given class based on knowledge of what the students in previous classes have done. In some situations, it may be possible to state, in advance, that scores in a particular range will receive a particular letter grade. Even so, the grading "curve" is based on tacit expectations from past experiences. Once you understand that the purpose of exams is to measure how much you know relative to other students, it should be clear that an item that everyone gets right (or wrong) is of no measurement value. A good exam will have some items that only the worst students should miss, and other items that only the best students should get right. Your goal is to get a few more right than the other students do.