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METHOD

INTRODUCTION

What is Lost in Prosopagnosia: Can a Prosopagnosic Distinguish Sheep?�Alexander R. Toftness & Eric. E. Cooper�Department of Psychology, Iowa State University, Ames, IA, USA

RESULTS

• LB showed evidence of a deficit to the identification of both people and sheep. This runs counter to McNeil & Warrington’s (1993) conclusion that prosopagnosia is a disorder specific to human faces.
• LB’s deficit disappears when she can use a surface cue (white vs. speckled comparisons) which can be explained by the coordinate relations hypothesis, but not a face-specific account.
• LB was impaired at sheep recognition both when just the face of sheep were used, and when whole bodies were used, suggesting that the recognition deficit is not unique to faces.
• LB showed a conservative response bias (i.e., was more likely to say “not same” than “same”) to simultaneously presented photos. This shows that she was impaired at attaching identical identities to two photos from different angles for both people and sheep.

Cooper, E. E., & Wojan, T. J. (2000). Differences in the coding of spatial relations in face identification and basic-level object

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Neuropsychologia, 29(2), 185–193.

Gauthier, I., & Tarr, M. J. (1997). Becoming a “Greeble” expert: Exploring mechanisms for face recognition. Vision

Research, 37(12), 1673-1682.

Gauthier, I., Tarr, M. J., Moylan, J., Anderson, A. W., Skudlarski, P., & Gore, J. C. (2000). Does visual subordinate-level

categorisation engage the functionally defined fusiform face area? Cognitive Neuropsychology, 17(1-3), 143-164.

Kanwisher, N., & Yovel, G. (2006). The fusiform face area: A cortical region specialized for the perception of faces.

Philosophical Transactions of the Royal Society B: Biological Sciences, 361(1476), 2109-2128.

McNeil, J. E., & Warrington, E. K. (1993). Prosopagnosia: A face-specific disorder. The Quarterly Journal of Experimental

Psychology, 46(1), 1-10.

CONCLUSION

REFERENCES

To contact the first author email toftness@iastate.edu

Participants (in both experiments):

• One acquired prosopagnosic (LB), 34 student control participants, and one age-and-sex-matched control participant.

Procedure:

• Participants completed a simultaneously-presented discrimination task with 2 side-by-side photos. In half of the trials, photos were of the same individual, but different viewpoints. Otherwise, the photos were of 2 different individuals. The participants responded “same” or “not same.”
• Experiment 1 used photos of legislators, and Experiment 2 used sheep.
• Trials included manipulations of facial features (clean-shaven vs. mustachioed humans & white-faced vs. speckled-faced sheep), and the use of sheep faces vs. sheep bodies (in Exp. 2).
• Comparisons were made within feature groups (i.e., shaven-shaven, mustachioed-mustachioed, white-white, & speckled-speckled) and between feature groups (i.e., shaven-mustachioed & white-speckled).

Predictions:

• Relative to controls, LB should be impaired overall in both experiments. LB should not be impaired at white-speckled trials. LB should be impaired at both face and body sheep trials.

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• The disorder of prosopagnosia is sometimes referred to as ‘face blindness” because of the loss of the ability to identify faces.
• However, extensive evidence points to additional perceptual deficits in prosopagnosia. What exactly is broken in a prosopagnosic brain?

Previous Work (McNeil & Warrington, 1993)

• Found that a sheep farmer could recognize his sheep despite being unable to recognize people. The findings of McNeil & Warrington have been influential, despite problematic methods. For example, they used the same photos for learning and testing; the photos had identifiable features other than identity (e.g., spots, background). The present work sought to improve those methods to better answer the question of face-specificity.

Face-Specificity Hypothesis (e.g., Kanwisher & Yovel, 2006)

• Posits that prosopagnosia’s deficit is specific to human faces.

Coordinate Relations Hypothesis (e.g., Cooper & Wojan, 2000)

• Posits that prosopagnosia is a deficit of a system of coordinate processing that is used when the parts (and relations between those parts) of objects match, thus requiring metric processing. In other words, if identification can’t be accomplished with features alone, then coordinates are used.

Note: For the control group, the number given is expressed as the mean percent correct. Trial types where shaven-mustachioed or white-speckled comparisons were made had no trials where “Same” was the correct response. White, white-speckled, and speckled trials are collapsed across face and body trials. Face and body trial types are collapsed across white, white-speckled, and speckled trial levels. LB’s significant differences from the control group (p <.05) are denoted with asterisks. The matched control was matched for age and sex. On the graphs, error bars are 95% confidence intervals.