Abstract
The fundamental challenge in facial recognition lies in understanding the role that different facial features play in our judgments of identity. Notable in this regard are the relative contributions of the internal features (eyes, nose and mouth) as well as the external features (hair and jaw-line). Past studies that have investigated this issue have typically used high resolution images or high quality line drawings as facial stimuli. The results obtained have therefore been most relevant for understanding the how faces are identified at close range. Given that real-world viewing conditions are rarely optimal, it is important to know how image degradation (such as loss of resolution caused by large viewing distances) influences our ability to perceive those internal and external features. We report experiments designed to address this issue, and our data characterizes how the relative contributions of internal and external features change as a function of image resolution and viewing distance. While we have replicated results of previous studies that have shown internal features of familiar faces to be more useful for recognition than external features at high resolution, we found that the importance of the two feature sets is flipped as resolution decreases. Additionally, our results suggest that the visual system uses a highly non-linear cue-fusion strategy in combining internal and external features along the dimensions of image resolution and distance, and that the configural cues that relate the two feature sets play a profoundly important role in judgments of facial identity.