What's a Greeble and what can you do with it?

The Greebles form a category of computer-generated novel objects that were originally designed as a control set for faces, so that people could be trained to become "Greeble experts". Although they have been associated with research arguing that faces are only "special" because of our expertise with them, these novel objects have been used for other purposes too. Like for any research question, research on why faces appear to be special should not rely too extensively on a single category and other research on this issue relies on expertise with real objects like cars, birds or dogs. Nonetheless, the Greebles have been an exceptionally useful set of stimuli and this web site summarizes some basic information about them.

Like faces, Greebles are all similar because they have the same number of parts in the same configuration.Although they may have properties in common with faces (bilateral symmetry, organic-like characteristics) the Greebles are apparently not treated as faces by our visual system. One example of this is that patient CK  (Moscovitch, Winocur & Benrmann, 1997) who performs normally with any face-like stimuli (including cartoons such as Bart Simpson and Donald Duck, and faces made of fruits!) but is very poor at recognizing any other object, treats Greebles like objects (Gauthier, Behrmann & Tarr, 2004). Nonetheless, to address some reasonable concerns about the role of symmetry and a face-like configuration in the use of Greebles, we later created a whole set of asymmetrical Greeble stimuli (both the symmetrical and asymmetrical sets can be obtained from Michael Tarr).

Normal subjects without any experience with these objects appear to process Greebles in a part-based fashion comparable to the way they recognize other non-face objects. However, research with Greebles has shown that after people become experts at recognizing individual Greebles, they then process Greebles in a holistic and configural fashion, similar to the way we tend to treat upright faces (Gauthier & Tarr, 1997; Gauthier & Tarr, 2002). Greeble experts also activate their "fusiform face area" in the brain more than novices do (Gauthier, Tarr, Anderson, Skudlarski & Gore, 1999): this suggests that this part of the brain may be specialized for faces because of our experience with them, not because of some innate bias.
 

The Greebles were created by Scott Yu at Yale University, under the supervision of Michael J. Tarr and Isabel Gauthier. They were initially created for use in Gauthier's dissertation work and first appeared in a published article in Gauthier and Tarr (1997).Jerome Harris and Michael Oneppo designed the asymmetric versions at Brown University based on Scott's originals (both the symmetrical and asymmetrical sets can be obtained from Michael Tarr).

The set has been revamped a few times, and changes in rendering capabilities have made for the most noticeable changes, with the objects looking more and more realistic. The two Greebles in the top row are from what we call two different genders and are fairly easy to discriminate. Greeble experts learn to discriminate rapidly between individuals within the same gender and family (different families have different body shapes), such as the two guys in the bottom row.

Research featuring Greebles

It is somewhat difficult to keep track of this, but this is a list of research articles that used Greebles (some are review papers that discuss Greeble research). Note that the list is almost certainly incomplete. Several of these papers can be downloaded from the websites of Michael J. Tarr or Isabel Gauthier:

1• Gauthier, I., & Tarr, M. J. (1997). Becoming a "Greeble" expert: Exploring mechanisms for face recognition. Vision Research, 37(12), 1673-1682.
2• Williams, P., Gauthier, I., & Tarr, M. J. (1998). Feature learning during the acquisition of perceptual expertise [Commentary on Schyns, Goldstone & Thibault The development of features in object concepts]. Behavioral and Brain Sciences, 21(1), 40-41.
3• Gauthier, I., Williams, P., Tarr, M. J., & Tanaka, J. (1998). Training "Greeble" experts: A framework for studying expert object recognition processes. Vision Research, Special issue on "Models of Recognition", 38: 2401-2428.
4• Abelson, RP, Dasgupta, N, Park, J. Banaji, MR. (1998). Perceptions of the collective other. Pers Soc Psycholo Rev, 45(10): 1213-23.
5• Gauthier, I., Tarr, M.J., Anderson A.W., Skudlarski, P. & Gore, J. C. (1999). Activation of the middle fusiform "face area" increases with expertise in recognizing novel objects. Nature Neuroscience, 2(6): 568-573.
6• Tarr, M. J., & Gauthier, I. (2000). FFA: A flexible fusiform area for subordinate-level visual processing automatized by expertise. Nature Neuroscience, 3(8): 764769.
7• Rossion, B., Gauthier, I. , Tarr, M.J., Despland, P. , Bruyer, R, Linotte, S., Crommelinck, M. (2000). The N170 occipito-temporal component is delayed and enhanced to inverted faces but not to inverted objects: an electrophysiological account of face-specific processes in the human brain. NeuroReport.11(1): 69-74.
8• Rossion, B., Gauthier, I, Goffaux, V., Tarr, M.J., Crommelinck, M. (2002). Expertise training with novel objects leads to left lateralized face-like electrophysiological responses. Psychological Science. 13(3): 250-257.
9• Gauthier, I., & Tarr., M. J. (2002). Unraveling mechanisms for expert object recognition: Bridging Brain Activity and Behavior, JEP:HPP, 28(2): 431-446.
10• James, T. W. & Gauthier, I. (2003). Auditory and action semantic feature types activate sensory-specific perceptual brain regions. Current Biology, 13(20): 1792-6.
11• Duchaine, B. C., Dingle, K., Butterworth, E. Nakayama, K. (2004). Normal greeble learning in a severe case of developmental prosopagnosia. Neuron, 43(4): 469-73.
12• Palmeri, T. J., Gauthier, I. Visual Object Understanding. (2004). Nature Reviews Neuroscience, 5, 291-303.
13• Gauthier, I., Behrmann, M. & Tarr, M. J. (2004). Are Greebles like faces? Using the neuropsychological exception to test the rule. Neuropsychologia, 42(14): 1961-70.
14• Rossion, B., Kung, C.C., Tarr, M. J. (2004). Visual expertise with nonfacects leads to competition with the early perceptual processing of faces inteh human occipitotemporal cortex, PNAS, 42(14): 1961-70.
15• Behrmann, M., Marrota, J., Gauthier, I., Tarr, M.J. & McKeef, T. J. (2005). Behavioral change and its neural correlates in visual agnosia after expertise training. Journal of Cognitive Neuroscience, 17(4): 554-68.
16• Vuong, Qc, Peissig, JJ, Harrison, MC, Tarr, MJ (2005). The role of surface pigmentation for recognition revealed by contrast reversal in faces and Greebles. Vision Research, 45(10): 1213-23.
17• Wagar, B. M. & Dixon, M. J. (2005). Past experience influences object representation in working memory. Brain and Cognition, 57: 248-256.
18• Cox, D.D., Meier, P., Oertelt, N., & DiCarlo, J. J. (2005). 'Breaking' position-invariant object recognition. Nature Neuroscience, 8: 1145-1147.
19• Bukach, C. M., Bub, D. N., Gauthier, I. & Tarr, M. J. (in press). Perceptual expertise effects are not all or none: local perceptual expertise for faces in a case of prosopagnosia. Journal of Cognitive Neuroscience.
20• James, T.W., Shima, D.W., Tarr, M.J., & Gauthier, I. (in press). Generating complex three-dimensional stimuli (Greebles) for haptic expertise training. Behavior Research Methods, Instruments, and Computers.
21• Behrmann, M., Avidan, G., Leonard, G.L., Kimchi, R., Luna, B., Humphreys, K & Minshew, N. (2006).Configural processing in autism and its relationship to face processing. Neuropsychologia, 44: 110-129.
22• Hoffman, K. L., Ghazanfar, A. A., Gauthier, I., Logothetis, N. K. Category-specific responses to faces and objects in primate auditory cortex. in preparation.
23• Lahaie, A., Mottron, L., Arguin, M., Berthiaume, C., Jemel, B., Saumier, D. (2006). Face perception in high-functioning autistic adults: evidence for superior processing of face parts, not for a configural face-processing deficit. Neuropsychology, 20(1): 30-41.