Configural and featural facial information: integrality in normal face processing, separability in prosopagnosia

Adults' expertise in face recognition has been attributed to their ability to engage in holistic processing. Exactly what constitutes holistic processing has remained controversial, however. In an attempt to understand the nature of face representation and processing, we examined how configural and featural information interact during face processing in a group of individuals with congenital prosopagnosia (CP) and matched controls, using Amishav and Kimchi's (2010) version of Garner's speeded classification task. This task examines the ability to process one dimension of a multidimensional visual stimulus, while ignoring another dimension, using selective attention measures, and provides a powerful test of perceptual separability between stimulus dimensions. When classifying upright faces varying in features (eyes, nose, and mouth) and configural information (inter-eyes and nose-mouth spacing), normal observers evince symmetric Garner interference: they were unable to selectively attend to features without experiencing interference from irrelevant variation in configuration, and vice versa, indicating that featural information and configural information are integral in normal face processing. In contrast, the CPs showed no Garner interference: they could attend to configural information without interference from irrelevant featural information, and vice versa, indicating that featural information and configural information are perceptually separable in CP's face processing. These results indicate that CPs do not perceive faces holistically; rather, they process featural and configural information independently. This finding not only elucidates the underlying perturbation in CP but also confirms that intact face processing is characterized by the perceptual integrality of configural and featural information