Lazarte A. &Schonemann, P. H.
Saliency metric for subadditive dissimilarity judgements of rectangles
Perception & Psychophysics, 1991, 49, 142-158
Previous findings that dissimilarity judgements for rectangles are strongly subadditive, that qualitative individual differences are always present, and that four-parameter psychophysical maps can reproduce the average ratings (Schonemann & Lazarte, 1987) are replicated.
However, the present study in addition suggests that the metric for bounded response transformation, previously used to restore additivity of responses, has a modest effect on the fits of the psychophysical maps. The differential weighting of the coordinates already incorporates segmental subadditivity predictions into the maps. In fact, the psychophysical maps define a subadditive saliency metric that depends on assigning larger weights to larger coordinates.
This constraint on the weights of these maps, together with the response times, allows us to identify a strategy shift when subjects respond to two classes of stimulus pairs: For rectangle-rectangle pairs, subjects center on the shape and size of the rectangles; for square rectangle pairs, the focus is on height and width.