The strength of visual priming of briefly presented gray scale pictures of real world objects, measured by naming reaction times and errors, was independent of whether the primed picture of the object was presented in the same or different size than the original picture.
These findings replicate Biederman & Cooper’s (1992) results on size invariance in shape recognition, which were obtained with line drawings, and extend them to the domain of gray level images. Entry-level shape identification is based either predominantly on scale-invariant representations incorporating orientation and depth discontinuities which are well captured by line drawings, or both discontinuities and the representation derived from smooth gradual surface changes are scale invariant.