Perturbation of perceptual units reveals dominance hierarchy in cross calibration.

Bingham and Pagano (1998) argued that calibration is an intrinsic component of perception-action that yields accurate targeted actions. They described calibration as of a mapping from embodied units of perception to embodied units of action. This mapping theory yields a number of predictions. The authors tested 2 of them. The 1st prediction is that change in the size of perceptual units should yield a corresponding change in the slope of the relation between response distances and actual target distances. In Experiment 1, the authors tested this prediction by manipulating interpupillary distance (IPD) as the unit for binocular perception of distance using vergence angles. In Experiment 2, they manipulated eye height (EH) as the unit for monocular perception of distance using elevation angles. In both cases, the results confirmed the predictions. The 2nd prediction was that perceptual units should interact to cross calibrate one another according to a dominance hierarchy among the units. The theory predicts a more temporally stable unit is used to calibrate a less stable unit but not the reverse. EH units change frequently, but IPD units do not, so IPD should be dominant. Simultaneously available IPD and EH units were perturbed successively (without feedback). As predicted, EH was recalibrated by IPD, but IPD was not recalibrated by EH. The mapping among units theory of calibration was thus supported.