Identifying and Controlling Biases in Subjective Judgments
Psychophysical experiments have shown that people can make accurate and internally consistent judgments of phenomena. This is the case, at least, with laboratory experiments concerned with lights or noises in which the person has no particular stake. Judgments about health may not be so dispassionate: in real life, people often have a personal stake in the estimation of their health. Bias refers to ratings that depart systematically from true values. We should, however, be careful to discriminate between two influences in the judgment process. There is the underlying and consistent perceptual tendency to exaggerate or underestimate stimuli described by the exponent b of the psychophysical experiments. This may also be applicable to health; we know little about this as yet, although several studies have compared subjective responses with physical or laboratory measurements of health status (75). A tendency also exists to alter response to a stimulus across time or under different situations, and this is termed bias. One person may exaggerate symptoms to qualify for sick leave or a pension, whereas another may show the opposite bias and minimize ailments in the hope of returning to work. Subjective ratings of health blend an estimate of the severity of the health problem with a personal tendency to exaggerate or conceal the problem—a bias that varies among people and over time.