The relativity of ‘absolute’ judgements

Suppose that, with rather few exceptions, the assignment of a number to a stimulus on one trial of a magnitude estimation or category judgement experiment serves as the point of reference for choosing an appropriate assignment on the next trial. This principle of relative judgement—relative to the immediate context—is developed to generate models for both magnitude estimation and category judgement experiments. It is applied, in particular, to the explanation of three, hitherto unrelated, phenomena: these are (a) the limited transmission of information in category judgements; (b) sequential constraints on the resolving power of category judgements; and (c) the autocorrelation of successive numerical magnitude estimates. Finally, some comparison is made between the principle of relative judgement introduced here and other contemporary ideas which have been addressed to one or more of these three critical phenomena.