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<\/p>\nWe often forget many things in our lives.\u00a0 We forget where we left our keys as we\u2019re running out the door in the morning; we forget what we had for breakfast; and sometimes we even forget what day it is.\u00a0 But one thing it seems we can always rely on is our ability to remember and discriminate between different faces.\u00a0 Our ability to recognize faces takes place without us even realizing it.\u00a0 It is something we take for granted because it is a very basic part of being a human being\u2014recognizing the people in our world\u2014our close family and friends who we see often, and even people we only encounter occasionally.<\/p>\n
Because we are so good at recognizing faces, scientists have long wondered whether there are specific areas in the brain dedicated solely to facial recognition, or, rather, if there are more generic areas in the brain that recognize all things that we have a lot of experience with, and are in turn \u201cexperts\u201d at (one such thing being faces).<\/p>\n
But how do you even go about testing something like this?\u00a0 It may seem easy, but it is actually quite a challenging and intriguing dilemma.\u00a0 It may seem that all you would need to do would be to compare people\u2019s ability to recognize faces with their ability to recognize other objects, but that would only answer half the question.\u00a0 A difference in ability doesn\u2019t give any insight into whether there is a specific area or process in the brain specialized to just<\/i> faces.<\/p>\n
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In order to be able to identify whether there is something in the brain specifically targeted on faces, you would need to somehow be able compare people who have an impairment in facial recognition with the rest of the \u201cnormal\u201d population in terms of their ability to recognize faces versus their ability to recognize some other object.\u00a0 \u00a0You\u2019d want to see if their ability to recognize objects other than faces was identical to individuals without the impairment.\u00a0\u00a0 It turns out such individuals exist.\u00a0 Prosopagnosia, or face blindness is a condition in which one\u2019s ability to recognize faces is impaired.<\/p>\n
So you have your two populations to compare: those suffering from prosopagnosia and those with no recognition impairments. \u00a0And you have your experiment: compare visual recognition of faces and other objects between prosopagnosics and normal people.\u00a0 But here\u2019s where another challenge comes in.\u00a0 What object do you use as a comparison?\u00a0 It can\u2019t be just any object because people might have different skill at recognizing different types of objects.\u00a0 You have to compare the right things.\u00a0\u00a0 The point is you have to find an object to compare with faces that you can be confident that people are equally adept at recognizing in order to make a valid comparison.\u00a0 In this way you are weeding out the possibility that the difference is because of the object and not the person.<\/p>\n
So scientists studying face recognition chose bodies \u2013 the human form: faceless bodies, and headless bodies.\u00a0 It\u2019s not as creepy as it sounds; they used simple silhouette illustrations.<\/p>\n
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Source: Susilo et al., 2013<\/sub><\/p>\n \u00a0<\/sub><\/p>\n Previous research has proven that we are equally expert at recognizing the details and \u201cpatterns\u201d of the human form and the human face.\u00a0 We know this because of a phenomenon called the inversion effect.\u00a0 For objects that we have a great deal of exposure to, and therefore expertise at recognizing, our ability to recognize and distinguish differences in those same objects is impaired when they are inverted \u2013 in other words, upside down.\u00a0 Scientists regard this inversion effect as evidence of expertise (Robbins & Coltheart, 2012a; Yovel, Pelc, & Lubetzky, 2010).\u00a0 Think of it this way: if you saw an object for the first time it wouldn\u2019t matter if it was right side up or upside down; you would have no previous experience to compare it to\u2014you wouldn\u2019t know the difference.\u00a0 Therefore, it makes sense that if you were an expert at recognizing certain objects it would be more disorienting to see those objects upside down than to see novel objects inverted.\u00a0 By looking at inversion effects it becomes clear that we are not equally expert at recognizing all objects in our world.<\/p>\n But bodies provide the perfect comparison for faces.\u00a0 As it turns out, our inversion effects for bodies are equal to the inversion effect for faces.\u00a0 Scientists hypothesize that the reason we are equally good at recognizing human faces and the human form is because the human body and the human face both have consistent configurations in terms of the positions of the arms and legs, or the eyes, nose and the mouth\u2014you wouldn\u2019t find an arm sticking out of a head, or eyes on someone\u2019s chin.<\/p>\n Simply put: the \u201cnormal\u201d person has equal experience with recognizing faces\/bodies and is therefore an \u201cexpert,\u201d to the same degree with both.<\/p>\n In 2012 a group of scientists from three universities collaborated to test whether facial recognition was the result of a specialized brain mechanism.\u00a0 The experiment basically consisted of a comparison of people with prosopagnosia and those without on their ability to discriminate differences in pairs of images of faces, and of human forms when presented to them upside down or right side up.\u00a0 144 pairs of images were presented (72 inverted, and 72 right-side up).\u00a0 The experiments measured how accurately the participants were able to discern differences, and how long it took them to make these same\/different decisions.\u00a0 The face pairs differed in terms of the shapes of eyes, noses and mouths, while the body pairs differed in terms of positions of the arms, legs, and heads.<\/p>\n The control group in this experiment comprised 20 people from the Dartmouth College Community with ages ranging from 18-27.\u00a0 Having a control group was crucial because you can test people with face blindness all you want, but you have no way of knowing whether the results you\u2019re gathering are normal or not if you have nothing to compare them to.\u00a0\u00a0 The controls needed to serve as a kind of baseline\u2014to establish the norm.\u00a0 But first, the scientists had to make sure that the controls were actually normal.\u00a0 As I mentioned before, there are certain telltale signs that make us confident that humans are equally expert at recognizing\/discriminating faces and bodies, and so with this in mind, the scientists put the controls through the experiment to ensure that the results they received from them matched the norm they expected.\u00a0 And, sure enough, the controls were good.\u00a0 They were significantly better at discriminating between upright faces, faceless bodies, and headless bodies, than they were when the images were inverted.\u00a0 Moreover, this discrimination took them longer when the objects were inverted than when they were right side up.<\/p>\n The only step remaining was to compare the results of the prospagnosics and the controls.\u00a0 Here\u2019s what they found: overall the prosopagnosics were equal in their recognition of bodies to the control, and they had equal level of expertise (same size inversion effects), but at the same time they were less accurate at noticing differences in face pairs, and also slower.\u00a0\u00a0 Clearly facial recognition was somehow different than recognition of other objects.<\/p>\n Through the experiment the scientists successfully showed that the differences in the two groups were not caused by a difference in level of expertise, or by an overall difference in recognition ability of all objects between the two groups.\u00a0 The only possibility left was that there must, in fact, be a specific region or process in the brain specialized for recognizing faces.<\/p>\n Now if they could only discover the part of my brain specialized at remembering where I left my keys!<\/p>\n References<\/p>\n Robbins, R. A., & Coltheart, M. (2012b). Left\u2013right holistic integration of human bodies. Quarterly Journal of Experimental Psychology, 65, 1962\u20131974.<\/p>\n Susilo,Tirta., Yovel., Galit, Barton., J.S. Jason., & Duchaine, Bradley (2013). Face perception is category-specific: Evidence from normal body perception in acquired prosopagnosia, 88-94.<\/p>\n Yovel, G., Pelc, T., & Lubetzky, I. (2010). It\u2019s all in your head: Why is the body inversion effect abolished for headless bodies? Journal of Experimental Psychology: Human Perception and Performance, 36, 759\u2013767.<\/p>\n