[3] The greebles were created for Isabel Gauthier's dissertation work at Yale,[4] so as to share constraints with faces: they have a small number of parts in a common configuration.
[7] Twelve undergraduates of Oberlin College were offered participation in the initial facial rotation experiment, wherein they took part in a rigorous training exercise, with the goal being the creation of experts in recognizing greebles.
Experimentation was divided into one-hour sessions over the course of two weeks, for a total time of 9 hours.
Two subjects bearing prosopagnosia proved to be far more capable at the recognition of greebles than human faces, the latter faculty being a severe disability.
Consequently, the study evinced questions regarding the mechanisms of human facial recognition, and whether this facility applies to faces alone, or other object classes.