Named by the American psychologist Robert Abelson, the Greebles were created for cognitive neuroscientist Isabel Gauthier’s dissertation work at Yale. Twelve undergraduates of Oberlin College were offered participation in this initial facial rotation experiment, wherein they took part in a rigorous training exercise, with the goal being the creation of experts in recognising Greebles (30 were employed in this initial experiment). For the second test, the Brightness-Reversal Test, ten of the original participants were joined by 12 undergraduates of Brown University. Each Greeble was assigned a meaningless name, each starting with a unique letter. The Greebles were viewed on Macintosh computer monitors of 72 pixels per inch.
Experimentation was divided into one-hour sessions over the course of two weeks, for a total time of nine hours. Results found the process of Greeble recognition differed from that of facial recognition. 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.
The study remains remarkable because Gauthier demonstrated that, after training participants on the many aspects of Greebles, the fusiform face area in the participants’ brains responded just as well to Greebles as it did to human faces. This suggests that people can improve their ability to recognise faces and objects and that the fusiform face area is not strictly used for recognising human faces. Greebles are now often used in mental rotation task experiments.