GROUP AND INDIVIDUAL VARIATIONS IN JUDGMENT AND THEIR RELEVANCE TO THE SCALING OF GRADUATED CIRCLES

Widely disparate opinions have been expressed about the need for and value of the perceptual scaling of graduated (proportional) circles. This continuing debate has concentrated on the measurement of the power law exponent derived from the average estimates of subject groups, with the implicit assumption that the identification of the 'correct' value for this exponent would ensure effective cartographic communication. Average exponents derived from a range of experiments have exhibited wide variety. The analysis of experimental data indicates that this variation is also a characteristic of individual subjects. The character and dimension of inter-subject and intra-subject variation are such that the employment of perceptual rescaling for graduated circles appears to provide little overall benefit. Indeed, it appears to prejudice the performance of the most consistent judges. Les opinions sont tres partagees au sujet du besoin et de la valeur de graduer la perception des cercles proportionnels. Ce debat ou...