Debunking myths on genetics and DNA

Saturday, November 26, 2011

I know that face! Sort of...

In graduate school I had a Chinese friend who one day asked me the name of the fellow student who'd just stopped by to borrow a book. I told her, she thanked me, and added, "It's so hard for me to remember faces. You guys look all alike to me."

Now, you have to understand that I'm petite, brunette with dark eyes (very Italian), and the girl she'd just asked about was the typical Northern European type, tall, blond, and blue eyes. The concept was truly intriguing. I tend to mix up Eastern Asians, but that day I learned that Asians tend to mix up Caucasians.

You may have noticed this in other contexts, for example when people tell you who you or your child looks like and they come up with the funniest things. However, the "other-race" effect (less accurate recognition of people of a different race than self) is real and has been documented in the literature [1,2]. In these studies, participants were presented faces from different ethnic groups, including their own. In a second phase, a mix of already observed and never-seen before faces was presented, and participants had to recognize which they had already seen. In [1], researchers measured different brain potentials (through EEG) and inferred a pattern between the potential intensities with the act of remembering a face:
"Individuation may tend to be uniformly high for same-race faces but lower and less reliable for other-race faces. Individuation may also be more readily applied for other-race faces that appear less stereotypical. These electrophysiological measures thus provide novel evidence that poorer memory for other-race faces stems from encoding that is inadequate because it fails to emphasize individuating information."
An event-related potential (or ERP) is a brain response to a stimulus (the faces, in this particular case). They are measured through EEG and they have several components as shown in the figure below (P1, N1, P2, N2, and P2):

In [1] researchers found interesting patterns between two components in particular, P2 and N200, and the ability to recognize a face:
"Among all the potentials examined, frontocentral N200 potentials and occipitotemporal P2 potentials were particularly informative because they yielded other-race-specific memory findings. We thus propose that these potentials indexed face individuation that tended to be uniformly high for same-race faces but lower and more variable for other-race faces."
Even though I don't have the expertise to understand all the technicalities presented in the paper (but I do welcome comments, if anybody out there wants to provide more insight), I find these results quite intriguing. For example, participants were also asked to rate the "racial typicality" of each face, and other-race faces that were "less typical" seemed to be easier to recognize. Also, the amount of exposure of an individual to the other-race group affects the results, as the brain can indeed train itself to recognition.

A curious trivia is that both studies state at the beginning that all participants were right-handed. Is there a reason for this? Does being left-handed introduce a bias in this kind of studies?

[1] Lucas, H., Chiao, J., & Paller, K. (2011). Why Some Faces won't be Remembered: Brain Potentials Illuminate Successful Versus Unsuccessful Encoding for Same-Race and Other-Race Faces Frontiers in Human Neuroscience, 5 DOI: 10.3389/fnhum.2011.00020

[2] Herzmann, G., Willenbockel, V., Tanaka, J., & Curran, T. (2011). The neural correlates of memory encoding and recognition for own-race and other-race faces Neuropsychologia, 49 (11), 3103-3115 DOI: 10.1016/j.neuropsychologia.2011.07.019

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