Recognizing Humans

Facial recognition is not fully understood. However, its importance is well known because it is needed in our day-to-day interactions with others and because the ability to rapidly distinguish safe, familiar faces from potentially dangerous, unfamiliar faces serves an evolutionary advantage. The mechanisms underlying facial recognition and object recognition are suggested to be distinct and independent. This is evidenced by the existence of prosopagnosia, or "face blindness". Individuals with prosopagnosia are unable to identify people by faces alone, but their ability to recognize objects usually remain intact.

It is further known that those with autism spectrum disorder tend to exhibit atypical face processing. This atypical processing tends to present itself early in childhood. Maggie Guy conducted a study that compares facial processing in infants who have siblings with ASD (autism spectrum disorder) and infants with FXS (fragile X syndrome) with those at low risk for ASD (control group). She recorded the electrical activity of these infants while presenting them with items and faces. They exhibited N290 and P400 responses, both of which are ERPs (event-related potentials) associated with face recognition. She concluded that N290 and P400 are both present when infants observe a human face, with a greater amplitude when observing a familiar face compared to an unfamiliar face. In addition to this, previous research has shown that another ERP known as N170 is also associated with facial recognition in adults. N170 is present when participants observe a human face; but adults with ASD exhibit a delay for the N170 to peak compared to controls.

In an article written by Anna Bobak and Sarah Bate in Scientific American, the writers describe the most recent research attempts to understand facial recognition. Many of these studies turn to “super-recognisers”, individuals who are particularly adept at recognizing faces. One study attempts to compare the eye movements of super-recognizers and those with prosopagnosia with typical individuals. They found that when presented with a face, typical people tend to focus on the eyes; individuals with prosopagnosia tend to focus on the mouth; and super-recognizers tend to focus on the nose. This suggests that the center of the face may be the optimal area of observation for facial recognition to occur.

Additional facial recognition tasks demonstrate that super-recognizers may be subdivided into “super-spotters” or “super-matchers”. In the first of two experiments, participants were presented with a grid of faces followed by a line-up. They were then asked whether a particular target face that was previously observed in the grid was present in the current line-up. In a second experiment, participants were presented with 20 faces from good quality security footage. The faces were then re-presented under poor lighting, and participants attempted to recognize the faces they had previously seen. Super-recognizers performed better than typical participants in both of these tasks, but it was found that the super-recognizers who were proficient at the first task did not necessarily perform well on the second task. This suggests that the facial recognition system may be divided further into additional mechanisms than simply holistic integration of faces. While these recent findings suggest that facial recognition requires multiple mechanisms and that there are indeed behavioral differences in how we observe faces, there are no conclusions on how these mechanisms occur or where these behavioral differences arise. Additional research in this area may eventually provide a treatment for prosopagnosia, as well as perhaps a better understanding of atypical face processing that occurs in ASD.

Citations

Guy, Maggie W., et al. “Neural Correlates of Face Processing in Etiologically-Distinct 12-Month-Old Infants at High-Risk of Autism Spectrum Disorder.” Developmental Cognitive Neuroscience, vol. 29, 2018, pp. 61–71., doi:10.1016/j.dcn.2017.03.002.

Bobak, Anna K., and Sarah Bate. “Superior Face Recognition: A Very Special Super Power.” Scientific American, 2 Feb. 2016, www.scientificamerican.com/article/superior-face-recognition-a-very-special-super-power/.