Wednesday, November 24, 2010

Gladly Making An Exception

Like Groucho Marx, some people never forget a face.* I, on the other hand, seldom recall one, or at least not right away. Several introductions are usually required before I can properly recognize somebody. I can talk to a new person directly for a decent length of time, at a job interview for instance, and then fail to recognize them when I pass them on the street the next day. As you can imagine, it’s a bit embarrassing. The list of social faux pas I’ve made as a result of this problem is lengthy and often absurd. Most famously, I once tried to strike up a conversation with a guy I’d already been on a date with. Even after he politely told me that we’d already met, it took me a few minutes to place where I’d last seen him. In my defense, he’d changed his hair…well, or maybe just his coat. Something. Whatever detail had been disrupted instantly rendered him a stranger to me. In a more practical social universe, everyone would have dramatic features or distinguishing accessories that they always wore. Better still, they would each just wear the same outfit every day, because it is far easier to identify a shirt than a face.

My difficulty recognizing faces is relatively mild. I can eventually commit a new face to memory, it just takes a frustratingly long time. But there are those for whom the situation is far worse. In 1947 neurologist Joachim Bodamer introduced the term prosopagnosia to describe the inability to identify faces. The condition, which also goes under the more pronounceable nickname “face blindness”, can be so severe that those afflicted with it struggle to recognize life-long friends, family members or even their own faces in the mirror. Like most of the exotic maladies I opt to write about, prosopagnosia is not especially common, affecting perhaps 1 or 2% of the population. However, researchers have only recently started paying attention to milder forms of face blindness, so it’s difficult to say how many more people like me are walking around oafishly ignoring acquaintances at the grocery store and inadvertently snubbing potential employers.

AP vs. CP
Face blindness comes in two flavors. Acquired prosopagnosia (AP) was the first to be described and, as its name suggests, is brought on by some sort of calamity (often a stroke or a head injury) after any number of years of prior normal face recognition. Congenital prosopagnosia (CP) begins at birth and seems to run in families. There are some curious differences between the 2 variations. Notably, individuals with AP have been found to have abnormal FFA activity when viewing faces. CP individuals however generally exhibit no FFA abnormalities when subjected to similar tests. “This would be fascinating,” You’re thinking, “if I actually had any idea what the FFA was.”

What The FFA
In reality you’ve probably heard of this already, though perhaps not by its proper name. The letters stand for Fusiform Face Area, but the person who told you about it at a party may have called it by some approximation such as, “that special face part of the brain”. The FFA is a region of the visual cortex thought to be specialized for the processing of face images. fMRI brain imaging has shown the FFA to be more active in subjects when viewing faces than when viewing various other objects and body parts (namely human hands). Since first being described in the 1990s, the function of the FFA has been debated, with some studies showing that it is also active during the viewing of non-face objects by viewers who are “experts” in these objects (automobile enthusiasts looking at cars, bird-watchers looking at birds, etc.). But face stimuli continue to elicit strong FFA responses in normal subjects and thus brain imaging of this region is a must for any self-respecting experiment hoping to shed light on prosopagnosia.†

Don’t bother looking it up. No reasonable dictionary or spell check would except “faceness” as a word. It’s just the folks in the laboratory playing with neologisms again. What they’re trying to convey with this term is the nebulous quality that can make a non-face object appear face-like. Humans excel at finding face imagery in objects that are in no way related to faces of our species or any other. Clusters of shapes that evoke faces are almost suspiciously ubiquitous. People see faces in clouds and wood grain and rock formations. They see a man on the moon and the Virgin Mary on a grilled cheese sandwich.‡ The reported prevalence of car-shapes or chair-shapes in abstract patterns is much lower. Clearly there is something special about the structure of a face. Not only are we prone toward perceiving face-shapes, but the FFA in more active when viewing objects with higher levels of “faceness”, even though it is well understood that they are not actual human forms. Unless you suffer from severe face blindness, your own FFA probably lit up when it saw the 3 electrical outlets used to dress up this article (and would have done so even had I not added facial expressions to them). What is it about such shapes that so readily captures your imagination? Without going into a lot of evolutionary speculation as to the benefit of being able to spot a face, I can relay to you experimental findings of what kinds of shapes get the most FFA response. They are symmetrical shapes with more elements in the upper portion than the lower portion. Basically something approximating 2 eyes on top and 1 mouth on the bottom, like so…   ^_^

Trees vs. Forests
There is some speculation that congenital prosopagnosia (CP) may be associated with deficiencies in global processing. Certain patterns can be viewed on a global and local level. A common experimental model of global vs. local perception is nested letters, in which larger letters are built out of smaller ones. These can be built using matching or non-matching nested letters.

Normal subjects tend to identify both global and local elements more quickly when they are matched (a large letter F made from small letter Fs, rather than from small letter Ts). With unmatched nested letters, global information can interfere with processing of local information and vice versa. In such cases, normal subjects are faster at spotting the global shapes (big letters) than the local shapes (smaller nested letters). The reverse trend has been observed in some individuals with CP. Not only did these subjects have more trouble spotting the large letters in the non-matched nested-letter stimuli than those in the control group (individuals with normal ability to recognize faces), but they were actually faster than the control group at identifying the smaller local letters, even in the non-matched scenarios. It is as though people with CP barely notice the global pattern and instead make a beeline for the interior details. In a face, the local elements are individual features - eyes, nose, mouth – while the global element is the entire face. Recognizing a face relies more on noting the configuration of the parts within the whole (are the eyes set wide or narrow, is the chin long or short) than on scrutinizing the parts. Thus people with CP may be missing the global face by getting mired in the details of its features.

Identification vs. Expression
Another curious difference observed between people with acquired (AP) and congenital (CP) prosopagnosia is the ability or lack thereof to accurately perceive facial expressions. Individuals with AP are often as unable to recognize the expression on a face as they are its identity.  However, some CP individuals have been documented to perform as well as the control group on facial expression tasks while still being completely hopeless in facial identification tasks. What this means in day-to-day life is that while they might be able to spot that a face is angry, they still won’t be able to tell who the face belongs to. However, given that the mystery face may well be that of a friend or acquaintance, they should at least have a good guess as to why it is angry.

What About Me?
If the symptoms I’ve been describing sound distressingly familiar, it is possible that you may be afflicted with some degree of prosopagnosia. Unfortunately it’s a bit harder to test for face blindness than for colorblindness. Probably you should be talking to a neurologist, but if you’re like me (short on time and money) you might prefer to take your chances with the internet instead. I found an online test that was quick and painless enough. Though loudly proclaiming that it can’t actually diagnose you, it does offer some vague quantification in the form of a score and numbers indicative of normal vs. impaired facial recognition performance. Stunningly I got a 66, which puts me below average (71) but still well above impaired (47). Perhaps there’s hope for me after all.

What’s a person to do if they score closer to a 47? Not a whole lot, I’m afraid. Intentionally or not, individuals with face blindness often rely on non-face cues to help sort out who’s who. Hairdos, glasses, and style of clothing often do the trick (or at least until their wearers suddenly decide they need a new look). Mannerisms, voices and context help too (your professor is the one in the front of the class, your neighbor is the one in the adjacent lawn, etc). From my own experience I would offer that, especially if you’re female, smiling politely at anyone who smiles at you first is not always the best strategy. Though if someone addresses you by name, there’s a good chance you’ve met them, so just roll with it.

As for the rest of you (the 71 and over scorers), my apologizes if I didn’t say hello when you saw me at the movie theater last weekend. It’s nothing personal. You might consider getting yourself some sort of accessory that makes you more readily recognizable, like an eye patch or a cane or an electric blue feather boa. It would really help me out.

* The oft-repeated quote is, “I never forget a face, but in your case I’ll be glad to make an exception.” I have no idea which film (if any) it came from. I’m not a Marx brothers fanatic, I’ve just heard the quote here and there.

† Another brain region, the Occipital Face Area (OFA), also figures prominently into such studies. However, I already have far too many details to cram into one little article.

‡ The Virgin Mary sammich came into existence in 1994 but is predated by nearly 2 decades by Maria Rubio’s pioneering Jesus tortilla. For a while, the latter could be viewed at a shrine in New Mexico. However, since both the tortilla and the grilled cheese look like fairly non-descript faces rather than specific religious figures, you can probably just make your own lunchtime miracle using whatever is currently in your fridge.

Who told you this?

Kanwisher, N. et al. 1997. “The Fusiform Face Area: A Module in Human Extrastriate Cortex Specialized for Face Perception.” The Journal of Neuroscience 17: 4302-4311.

Tarr, M.J. and Gauthier, I. 2000. “FFA: a flexible fusiform area for subordinate-level visual processing automatized by expertise.” Nature Neuroscience 3: 764-769.

Caldara, R. and Seghier, M. 2009. “The Fusiform Face Area Responds Automatically to Statistical Regularities Optimal for Face Categorization.” Human Brain Mapping 30: 1615-1625.

Bentin, S. et al. 2007. “Too Many Trees to See the Forest: Performance, Event-related Potential, and Functional Magnetic Resonance Imaging Manifestations of Integrative Congenital Prosopagnosia.” Journal of Cognitive Neuroscience 19: 132-146.

Schiltz, C. et al. 2006. “Impaired Face Discrimination in Acquired Prosopagnosia Is Associated with Abnormal Response to Individual Faces in the Right Middle Fusiform Gyrus.” Cerebral Cortex 16: 574-586.

Humphreys, K. et al. 2007. “A detailed investigation of facial expression processing in congenital prosopagnosia as compared to acquired prosopagnosia.” Experimental Brain Research 176: 356-373.

Love, B.C. et al. 1999. “A Structural Account of Global and Local Processing.” Cognitive Psychology 38: 291-316.

Friday, November 12, 2010

Pretty and Witty and Bright

What can beauty buy for you these days? More dates and party invitations? Absolutely. Fewer speeding tickets? Sure. Better chances of being offered the job even after a so-so interview? You bet. How about a world that understands your many unique qualities, a world that pays attention to the nuances of your individual personality, a world that “gets” you? Quite possibly yes. Or at least your odds are better than that of your homelier friends. So says a recent study in which first impressions formed about attractive people were found to be more accurate than those formed about less attractive people.

In the study, groups of college students of varying degrees of physical beauty were allowed to interact for a scant 3 minutes, after which they attempted to assess each others’ personalities.* Additionally they rated the attractiveness of other members in the group and lastly answered questions about their own personalities. In order to minimize confusion and maximize judgmental shallowness, I have opted to divide the participants into two categories: pretty and ugly.† Researchers compared how subjects scored on positive traits (relative to the average) with their attractiveness score. They also examined the consistency of perceivers’ impressions of specific personality traits with the self-reported personality questionnaires of both pretty and ugly subjects. This latter phenomenon is called “distinctive accuracy”. Greater distinctive accuracy means that first impressions about a subject more closely match that subject’s own view of their personality. For instance, a person who thought himself to be very sociable but not as strongly intellectual would be seen this way by others, even if he was viewed as being more sociable and more intellectual than the “average” person.

Fig 1. Fake data that did not come from the study discussed here, or from any other study. Really. But it's easier on the eyes than the real data, which means you'll pay closer attention to it and rate it more favorably than if I'd shown you the actual data.

It has been observed numerous times that pretty people tend to be perceived as possessing more overall positive traits than ugly folk. Pretty individuals are seen as smarter, friendlier and generally just better than their ugly counterparts. This is termed the “attractiveness halo effect”. It was no surprise that the results of this new study followed the trend. Members of the group who were perceived to be prettier were also seen as being graced with larger servings of intelligence and other desirable traits. To remind us of the platitude that beauty is in the eye of the beholder, attractiveness ratings were not entirely unanimous. Some subjects were ranked as being ugly by the majority of participants, but still had one or two fans who found them attractive. Interestingly, in these cases, the ugly subjects also benefited from the halo effect. Those who rated an ugly subject’s appearance favorably, lavished equal praise on their inner qualities.

Results regarding distinctive accuracy featured a few more twists.‡ With all this talk about positive biases and preferential treatment, it is easy to assume that more attractive people would be viewed with less accuracy. Wouldn’t they just be seen as generically flawless? So lacking in imperfections that all their good qualities were uniformly present? In actuality, the results showed the opposite. Personality assessments for pretty subjects were more accurate (ie, better matched to the self-reported questionnaires) than those for ugly subjects. Why would this happen? The authors note two possible causative factors. One is that the pretty subjects may simply attract more attention from their perceivers. People want to connect with good-looking individuals, so they make more of an effort and in doing so manage to observe more detail. The other possible factor revolved around the person being perceived, the “target”, rather than the perceiver. In order for perceiver to glean information about the target, the target must first put out some sort of cues. The authors suggest that pretty targets, using the superior social skills of someone that spent a lifetime being beautiful, are more likely to make information about themselves available to the perceiver. For support of this idea, we go back to the subjects that were rated as ugly by most participants but as pretty by a few. As mentioned before, these subjects were viewed by their admirers as having more positive traits. However, they were not necessarily viewed with greater distinctive accuracy by these same admirers.§ While they benefited from the halo effect, they lacked the confidence to give their perceivers enough material to form accurate impressions about their personalities. They were too introverted to read.

This may not be the happiest news for mousey wallflower types. However, it’s mildly encouraging to hear that our ability as humans to accurately judge personality doesn’t completely shut down when we encounter physical beauty. Shallow and biased though we are, we can at least tell which of an attractive individual’s copious and remarkable positive traits are their most pronounced. We can differentiate that they are more generous than they are eloquent, for instance. Though, of course, they still possess greater generosity and eloquence (and intelligence and sociability and impressive math skills…) than the ugly person sitting next to them. We’re also not too bad at counting up who has more favorable personality traits when comparing two similarly attractive individuals. The trouble really starts when we are faced with a choice between the ugly but brilliant job candidate and the beautiful but incompetent one. But, as Oscar Wilde wrote, “it is better to be beautiful than to be good,” so even that is a simple enough problem to solve.

* This was accomplished via a 21-item questionnaire based on “Big Five” personality traits (openness, conscientiousness, extraversion, agreeableness, and neuroticism…which together make the acronym OCEAN, how cute) along with 3 additional questions about general perceived positive qualities.

† In reality they were rated on a 1-7 scale of attractiveness, and consensual attractiveness (the average of the ratings from the entire group for each subject) was considered along with subjects’ attractiveness ratings by individual perceivers. But we’ll get to that in a minute.

‡ Please recall one more time that distinctive accuracy is the weighing of specific personality traits relative to one another, rather than just an overall thumbs up given to all possible desirable traits.

§ We’re talking about the really ugly people now, the statistically ugly, not just the average Joes and plain Janes. These individuals were 1 standard deviation or more below the average level of attractiveness.

Monday, November 1, 2010

Species of the Month: NOVEMBER

After living in Austin for over a year and making several trips into the more wildlife-infested surrounding Hill Country, I had my first scorpion sighting right in town last spring. The animal wandered into a classroom where I was learning German, causing much surprise and standing up from chairs amongst the students. The scorpion was escorted out of the building before any stinging ensued, but since then I’ve heard 2 tales of painful scorpion stings from friends and decided that it was worth looking into the matter. Texas is home to about 20 species of scorpions, but Centruroides vittatus is the most commonly seen and the only one found throughout the state. It is one of a small handful of scorpion species recorded in the Austin area and its appearance is satisfactorily similar to that of the creature that briefly attended my German class back in April.

Physical Attributes

Like spiders and ticks, scorpions are arachnids. As such they have eight legs. Additionally they are equipped with a set of lobster-esque pinchers in the front and a long tail, complete with venomous stinger, in their rear half. The striped bark scorpion is yellowish to tan in color and wears 2 characteristic stripes down its back.* Adults average about 2.5 inches in length, with males somewhat predictably having longer tails.

Dining Habits

Like other scorpions, Centruroides vittatus eats primary insects. They eat a lot of things you probably don’t much care for including centipedes, flies, and spiders. They subdue their dinner by grasping it with their pinchers and then killing it with their venom-packed stingers. The actual eating part is a bit complicated. Scorpions have tiny mouths, so they do most of their digesting externally by coughing up digestive fluids onto their prey and then sucking up the liquefied remains. If it helps, you can think of it as akin to drinking a nutritious smoothie.

Hanging out

As I mentioned, Centruroides vittatus is the mostly commonly observed species of scorpion in Texas. It is also a species most commonly found in Texas. While striped bark scorpions live in various other US and Mexican states, Texas is headquarters for these critters. Being as they are not mammals, they must resort to behavioral thermoregulation. They tend to be more active at night and spend their days seeking shelter in cool, damp places (Texas summers are too hot even for scorpions). This can be any number of locations, from the undersides of logs and rocks to your air-conditioned apartment.

Courtship and Mating

Scorpions have a fancy mating ritual where they pair off, grab each other by the pinchers and do a little dance. At the end of their date the male drops a sperm sac on the ground, which the female scoops up into her abdomen.

Scorpions are pretty special arachnids in that they are oviviparous. That means they don’t lay eggs. The eggs remain in the body of the female until birth. Gestation for Centruroides vittatus is a lengthy 8 months, after which about 30 baby scorpions emerge. The mother carries the new brood on her back for a few days until they are ready to care for themselves, which you must admit is pretty cute by arachnid standards.† Striped bark scorpions live for about 4 years and will generally reproduce several times in their life.

At the Disco

Centruroides vittatus, as well as other scorpions, glow in under ultraviolet light (the “black light” seen in certain nightclubs). Needless to say, this is pretty cool. However it is not always advantageous to the animals. I noticed that several pest control websites sell a product called a “scorpion UV flashlight”, presumably used to find and stomp the little guys after nightfall.

Can They Hurt You?

They sure can. While no reasonable scorpion would mistake a human for their desired meal, they will sting you if you inadvertently surprise them during their normal activities.

Can They Kill You?

Of the well over 1000 known species of scorpion, only about 25 have venom toxic enough to kill a human.‡ Centruroides vittatus is not one of these species. As with bee stings, some people may have an allergic reaction to the venom. In these cases, death due to anaphylactic shock can occur when treatment is not sought. If difficulty breathing is one of the post-sting symptoms, paramedics should definitely be called to the scene. Such incidents are rare though. In most cases the sting of the striped bark scorpion just yields about 20 minutes of sharp pain followed by another day or so of mild discomfort. An ice pack helps.

Don’t Mow the Lawn Backward, and Other Sage Advice

I spoke to Venecia, one of the recent scorpion sting victims about her experience. She had been mowing the lawn when the attack occurred and was informed only after the fact that Hill Country wisdom recommends always pushing the mower forward in tall gross, so that any stinging creatures encountered will be preventatively puréed. Venecia unfortunately made a backward sweep and picked up a scorpion in her shoe. Shortly after she felt what she describes as “an intense stinging pain” accompanied by a “a burning sensation that doesn't subside”. Venecia described her assailant (which she shook from her shoe upon being stung) as dark brown and about 3/4 the size of a pinky finger, so it was probably not our friend Centruroides vittatus that got her, but another similarly non-lethal Texas scorpion.

In addition to modifying your lawn mowing style, the best way to avoid run-ins with scorpions around your house is to not create a lot of comfortable sheltering spots for them. Leaving logs, stones, building materials and trash around your yard can attract scorpions (not to mention cockroaches and raccoons). It’s also not a good idea to bring firewood into your home unless it’s going directly onto the fire. And you might consider a bit of weather stripping while you’re at it. In addition to keeping the scorpions out, you’ll waste less electricity.

* Technically, this would be “the upper surface of the abdomen”, but if I start using proper anatomical terminology to describe this thing, we’ll likely be here all day.

† Drinking blood (ticks), cannibalizing mates (spiders), etc.

‡ These belong to the family Buthidae, which is coincidently the same family in which Centruroides vittatus. Striped bark scorpions, luckily, so not share their relatives’ venom potency.