In a paper on underwater distortion of size Ross et al. (1970) report results which they claim to be at variance with a theory they attribute to Taylor. The so-called theory is actually a deduction from Taylor's theory of perception and, when it is correctly stated, it is confirmed by the reported results. The use of objective methods for the study of perceptual adaptation is criticized, and it is argued that subjective reports give a more accurate account not only of perceptual adaptation but of the adaptation of the behavioural system that is disrupted by any transformation applied to the retinal input.