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Face the Facts

We often forget many things in our lives.  We forget where we left our keys as we’re running out the door in the morning; we forget what we had for breakfast; and sometimes we even forget what day it is.  But one thing it seems we can always rely on is our ability to remember and discriminate between different faces.  Our ability to recognize faces takes place without us even realizing it.  It is something we take for granted because it is a very basic part of being a human being—recognizing the people in our world—our close family and friends who we see often, and even people we only encounter occasionally.

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 “experts” at (one such thing being faces).

But how do you even go about testing something like this?  It may seem easy, but it is actually quite a challenging and intriguing dilemma.  It may seem that all you would need to do would be to compare people’s ability to recognize faces with their ability to recognize other objects, but that would only answer half the question.  A difference in ability doesn’t give any insight into whether there is a specific area or process in the brain specialized to just faces.

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 “normal” population in terms of their ability to recognize faces versus their ability to recognize some other object.   You’d want to see if their ability to recognize objects other than faces was identical to individuals without the impairment.   It turns out such individuals exist.  Prosopagnosia, or face blindness is a condition in which one’s ability to recognize faces is impaired.

So you have your two populations to compare: those suffering from prosopagnosia and those with no recognition impairments.  And you have your experiment: compare visual recognition of faces and other objects between prosopagnosics and normal people.  But here’s where another challenge comes in.  What object do you use as a comparison?  It can’t be just any object because people might have different skill at recognizing different types of objects.  You have to compare the right things.   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.  In this way you are weeding out the possibility that the difference is because of the object and not the person.

So scientists studying face recognition chose bodies – the human form: faceless bodies, and headless bodies.  It’s not as creepy as it sounds; they used simple silhouette illustrations.

Source: Susilo et al., 2013

 

Previous research has proven that we are equally expert at recognizing the details and “patterns” of the human form and the human face.  We know this because of a phenomenon called the inversion effect.  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 – in other words, upside down.  Scientists regard this inversion effect as evidence of expertise (Robbins & Coltheart, 2012a; Yovel, Pelc, & Lubetzky, 2010).  Think of it this way: if you saw an object for the first time it wouldn’t matter if it was right side up or upside down; you would have no previous experience to compare it to—you wouldn’t know the difference.  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.  By looking at inversion effects it becomes clear that we are not equally expert at recognizing all objects in our world.

But bodies provide the perfect comparison for faces.  As it turns out, our inversion effects for bodies are equal to the inversion effect for faces.  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—you wouldn’t find an arm sticking out of a head, or eyes on someone’s chin.

Simply put: the “normal” person has equal experience with recognizing faces/bodies and is therefore an “expert,” to the same degree with both.

In 2012 a group of scientists from three universities collaborated to test whether facial recognition was the result of a specialized brain mechanism.  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.  144 pairs of images were presented (72 inverted, and 72 right-side up).  The experiments measured how accurately the participants were able to discern differences, and how long it took them to make these same/different decisions.  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.

The control group in this experiment comprised 20 people from the Dartmouth College Community with ages ranging from 18-27.  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’re gathering are normal or not if you have nothing to compare them to.   The controls needed to serve as a kind of baseline—to establish the norm.  But first, the scientists had to make sure that the controls were actually normal.  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.  And, sure enough, the controls were good.  They were significantly better at discriminating between upright faces, faceless bodies, and headless bodies, than they were when the images were inverted.  Moreover, this discrimination took them longer when the objects were inverted than when they were right side up.

The only step remaining was to compare the results of the prospagnosics and the controls.  Here’s 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.   Clearly facial recognition was somehow different than recognition of other objects.

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.  The only possibility left was that there must, in fact, be a specific region or process in the brain specialized for recognizing faces.

Now if they could only discover the part of my brain specialized at remembering where I left my keys!

References

Robbins, R. A., & Coltheart, M. (2012b). Left–right holistic integration of human bodies. Quarterly Journal of Experimental Psychology, 65, 1962–1974.

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.

Yovel, G., Pelc, T., & Lubetzky, I. (2010). It’s all in your head: Why is the body inversion effect abolished for headless bodies? Journal of Experimental Psychology: Human Perception and Performance, 36, 759–767.

To read the original article, click here

 

 

 

  1. March 19th, 2014 at 20:15 | #1

    Very thoroughly written post. I think it’s really interesting how face recognition is “special” and different than other pattern recognition. I’ve learned that researchers have identified the fusiform face area as the part of the brain activated during face recognition. However, other researchers found that dog experts showed inversion effect when shown pictures of dog faces upside down. So, it appears that the FFA is not a brain area exclusively for face recognition. This post makes me wonder some more about people with prosopagnosia. Studies have shown that people are equally good at recognizing parts of houses and whole houses, but much worse at recognizing parts of faces than whole faces. This shows that face recognition involves a lot of holistic processing. Since the study you reference found that prosopagnosia patients were overall worse at recognizing faces, I wonder whether they would be equally bad a recognizing parts of faces. Because they cannot recognize faces, would they not show as great of a difference between recognizing part of faces and whole faces?

  2. March 20th, 2014 at 22:56 | #2

    After learning about face recognition earlier this semester, this post caught my attention because it brought to light some of the lingering questions I had about prosopagnosia and the fusiform face area. For example, I thought the study that proved that most “normal” humans recognize faces as well as body figures was highly intriguing. This suggested that we become “experts” in pattern recognition, or more specifically in face recognition, because of increased contact. This coincides with the Harrison and Holes article we read for class about how contact can cause biases in face recognition, such as the “own-age bias” effect or the “own-race” effect. Evidence in that article about how frequent and recent contact increases face recognition could explain how repeated exposure is a driving factor that describes why we are “experts” in recognizing bodies as well. Surrounded by humans everyday, this inherent study also infers that we examine human bodies around us more than we think.
    This post was informative because it helped me understand prosopagnosia better in relation to someone without it. This has been hard to wrap my brain around since recognizing faces is a simple and automatic process that occurs in everyday life. Although, I do wonder why prosopagnosics were equal in recognizing bodies in comparison to the control group. My assumption would be that they would be better at recognizing bodies since their condition makes them strongly rely on other visual cues, such as hair, hands or body structure, to recognize people.
    This post successfully demonstrates evidence supporting a specialized region in the brain that recognizes faces, but I think it should also attack evidence that goes against the “special” quality of face recognition. For example, the “fusiform face area” of the brain, which is activated (Lights up) when someone recognizes a face, has also been shown to light up when an expert of some sort (Dog expert, car expert, etc.) recognizes the object that they are considered to be a specialist of.
    Overall, this was a wonderful post that was well laid out and interesting to read!

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