Phase- or energy-based face discrimination: some problems

Fourier analysis may be used to obtain the amplitude and phase spectra of images. Spectra from two images can then be recombined in an attempt to produce images with identical phase spectra but different amplitude spectra or with identical amplitude but different phase spectra. Kleiner and Banks (1987) and Kleiner (1987) used this technique to determine if the amplitude (energy) or phase characteristics of images form the basis for infant face preferences. This article describes how some of the procedures used by these researchers, for example, luminance normalization and photographic production of transparencies of images, probably prevented the images from having the desired characteristics, thus making interpretation of their studies very difficult. Additional potentially confounding issues to be addressed when repeating these or similar experiments are also discussed. These difficulties arise from the distinction between the numerical phase values obtained through the mathematical process and those that are visually effective.