Note on Sanders and Pacht's investigation of size constancy of clinical groups.

Abstract

In an investigation of perceptual size constancy of clinical groups, Sanders and Pacht [2] employed a rather unusual size-constancy index. The purpose of this note is to point out the differences between their index and those more commonly utilized and to demonstrate how its use is likely to be misleading.They reported mean constancy indices of 105 for a group of normals, 99 for a group of neurotics, and 88 for a group of psychotics. The technique they employed for measuring constancy was one in which the comparison stimuli were far and the standard near. 2 The comparison stimuli consisted of 13 black squares graduated in size and randomly arranged under a consecutive series of numbers. These squares were always present at a distance of five meters from the subject. The standard squares were of five different sizes and were presented individually at two distances from the subject, first at four meters and then at two meters. The subjects were instructed to choose the comparison square that was equal in size to the standard square.The following equation was utilized in obtaining the size-constancy index: Size-constancy index -• SizCfarSize near and Sizef ar refer to the judged size of the standard at two and four meters respectively. In order to eliminate negative scores and decimals, a constant of one was added to J The author wishes to thank Drs. M. Ray Denny and Paul D. Greenberg for their assistance and suggestions. However, the author assumes sole responsibility for the content of the note.