Gotcha! You can easily spot a familiar face in a crowd. But what if your mission was to pick out the face of someone you've never seen? Enter facial-recognition technology. (Physical/Life Science Technology/Vision).

Ever searched for a friend in the middle of a mall or football game? It may seem like a miracle when you finally spot him or her, but have you stopped to think about how you managed to single out the one face you were looking for amid a sea of strangers?

Humans possess an extraordinary visual system capable of learning and recognizing thousands of faces--even someone they don't know and have never seen: "If you want to train someone to recognize all 155 known terrorists on the U.S. government's list by their face alone, that's not a problem," says Bob Schmitt at Viisage, an identification-technology company in Massachusetts.

So in this age of heightened security from the potential threat of terrorism, you might think the government would train sharp-eyed special agents to comb airports or sports stadiums for suspicious characters. But, explains Schmitt, it would take thousands of trained officers to scan every face in a crowd for a person who may not even be there. Which is why the race is on for security companies to create revolutionary facial-recognition technology--which uses a video camera and computer to distinguish a person based on his or her unique "faceprint." "It's the only technology that can identify someone who's merely walking down the street," says Trevor Prout of International Biometric Group.

Facial recognition isn't nearly as precise as a fingerprint or iris (colored area of the eye) scan. So scientists are probing the biology behind the human eye with a single-minded goal: to create artificial-vision technology that surpasses human ability and zeros in on possible terrorists, criminals, or missing persons faster than you can blink.

EYE-D

While every individual face may be unique, all faces share common features--eyes, nose, mouth, and ears--in roughly the same place. That's why the brain has evolved to detect miniscule differences between individuals, such as the particular shape of the eyes and mouth, explains computer scientist Gary Cottrell of the University of California at San Diego. We learn to distinguish one another's features through experience--starting with Mom or Dad, then brothers and sisters--and eventually thousands of faces. "It's a monumental task," says Cottrell. "But the brain is equipped to handle it."

How does the brain do it? About one third of the organ is devoted to vision, says neuroscientist Marry Sereno at the University of California at San Diego. One section of the brain's cortex (gray outer layer of tissue) called the fusiform face area specifically recognizes faces. "There are 100 million cells involved in vision," says Cottrell, "and 1 million nerves linking the eye and the brain." Cells near each other in the retina eventually connect to cells in the primary visual cortex (see diagram, p. 19). "If someone presented a letter A to your eye, then opened up the back of your head where neurons are firing, they'd see a kind of fuzzy A on the back of your brain," says Cottrell.

As a visual signal flashes up a chain of cells, parts of an image become lines and curves, then shapes, like an eye or nose, and finally an entire face--all in about 20 milliseconds, or 10 times faster than the blink of an eye. The cells that fire are different for each object or shape you see--cells in the fusiform face area fire only in response to a face: "We've found cells that are activated only when you see toilet brushes and houses," says Cottrell. But it's the process of detecting subtle differences in the details of a face that scientists hope to perfect in face-ID technology.

DIGITAL DIMPLES

Facial-recognition programs are a series of calculations that tell computers how to "see" faces--for without proper programming, a computer can't distinguish between a celebrity and a rock (see photos, next page). First, however, programmers must enter a database (electronic storage space) of faces into the computer--the computer needs a stored photo of a particular person to make an ID. "Facial recognition can't find anyone if we don't have an image of them or know who they are," says Prout. College-testing centers could use a database of drivers-license photos, for example, to ensure no one attempts to boost a score using a smarter substitute: "At some point you might have your picture taken for verification when you show up to take the SAT," says Schmitt.

[ILLUSTRATION OMITTED]

Next, a video camera--the computer's eye--must locate a human face in a room cluttered with other objects. "This takes pretty sophisticated software, because it's the most difficult part of the process," Schmitt says. The software struggles to accomplish mechanically what the primary visual cortex does naturally: find edges and shapes that define an object.

When a computer pinpoints a face, a different program translates human physical features into a mathematical code, then seeks for a match in the database of coded faces. Each kind of facial-recognition program uses a different algorithm (step-by-step procedure for solving a problem) in order to match a face. Software made by Identix in New Jersey, for example, uses local feature analysts to compare faces. "The human face contains landmarks just like any city," says Identix president Joseph Atick. The software calculates distances between points on a face to create a mathematical map unique to each person.

Eigenface software uses model faces made by morphing common features from photos taken of people across the U.S. Instead of comparing the facial map directly to the database, the software first matches it to one of 128 models to narrow the field and speed up the process.

So far, computer-recognition systems have achieved only 5 to 10 percent of the accuracy of the human eye. "A human can recognize a feature you might not pick up on a computer," says Schmitt: The eye uses clues like scars and freckles that computers aren't programmed to recognize. And the task only gets harder if a person's image isn't exactly the same as his or her picture in the database--unlike a computer, human vision isn't confused by a tilted head, smile or frown, or aging.

Still, facial recognition technology is fast improving. "Computers don't play sports or date, so they can devote all their `brain power' to storing faces," says Cottrell. Within five years, he estimates: "The human is going to be left behind."

HOW COMPUTERS "SEE" FACES

Two popular methods in facial-recognition software turn the face into a math equation. Computers can match 60 million faces per minute to a database.

1 The computer recognizes a human face by identifying a pair of eyes and facial borders.

[ILLUSTRATION OMITTED]

Eigenfaces

2 The image is cut above the eyebrows and below the chin to eliminate features like hairstyle that change over time.

[ILLUSTRATION OMITTED]

3 This image is compared with 128 eigenfaces that represent common facial features. Those with features that most closely match the face are chosen.

[ILLUSTRATION OMITTED]

4 Faces from the database with those same features are compared to the original face until the person is identified.

[ILLUSTRATION OMITTED]

Local Feature Analysis

2 The computer pinpoints unique features, or "landmarks," in each face with a set of dots. From ear to ear, the human face consists of 60 to 80 landmarks that can identify it.

[ILLUSTRATION OMITTED]

3 The pattern, or "map," is compared with each coded faceprint in the database.

[ILLUSTRATION OMITTED]

4 Those faceprints that most closely match the face will be chose.

[ILLUSTRATION OMITTED]

EYE SPY

VISION IS A CHAIN OF EVENTS FROM THE EYES TO THE BRAINS

Light bounces off objects and enters the eye through the pupil. The lens focuses and inverts (reverses) an image (arrows A and B below) and projects it onto the retina, a screen of light-sensitive cells on the back of the eye.

[ILLUSTRATION OMITTED]

RETINA CELLS

Rod and cone cells absorb light in the retina, then release neurotransmitters (chemical signals) to neurons in the optic nerve, or bundle of neurons (nerve cells). The 125 million rods see only in black and white, and work best in dim light. Seven million cone cells see in color, and work best in bright light.

HUMAN VISION

What your eyes see is relayed to the brain via the optic nerve. From there, signals pass to the primary visual cortex. Visual areas occupy nearly one half of the surface area of the entire cerebral cortex, or the brain's gray matter.

[ILLUSTRATION OMITTED]

Did You Know?

* Facial recognition is one type of biometric technology, or tool that uses biological information to verify identity. Other biometrics include voice recognition, iris scanning, and fingerprinting.

* Facial-recognition technology was used to scan spectators as they entered the gates to the 2000 Super Bowl game in Tampa Bay, Florida. Officers identified 19 people with outstanding arrest warrants out of 70,000 fans.

* The popularity of biometric technology surged after Sept. 11, 2001, when the U.S. Department of Defense issued contracts for developing tools in response to the terrorist threat. Facial-recognition cameras have since been installed at points along the U.S.-Canada border.

Cross-Curricular Connection

Language Arts: Write a science-fiction story in which at least one biological-recognition technology is an important part of society.

Critical Thinking: Many critics of facial recognition are concerned that government use of the technology invades privacy and threatens personal freedom. Discuss the pros and cons of the government using facial-recognition technology. Then choose a side and organize a class debate.

Resources

To examine privacy issues involved with widespread use of facial-recognition technology and to learn how the industry is working to protect citizens visit: www.bioprivacy.org

A printable worksheet for students to label the parts of a human eye is available online at:

www.enchatedlearning.com/subjects/anatonmy/eye/label/labeleye.shmtl

Read a more detailed account, of different .types of facial-recognition technology and how it is used at:

www.howstuffworks.com/facial-recognition.htm

CHECK FOR UNDERSTANDING

Directions: Fill in the blanks to complete the following sentences.

1. Facial-recognition technology uses a -- and -- to identify a person's "faceprint."

2. At the moment, facial-recognition technology is not as accurate as these two other biometric technologies: -- and --.

3. The fusiform face area is located in the -- of this organ: --

4. Light bounces off objects and enters the eye through the --.

5. What your eyes see is relayed to the brain via a bundle of -- called the --.

ANSWERS

1. video camera, computer 2. fingerprint, iris scan 3. cortex, brain 4. pupil 5. neurons (or nerve cells), optic nerve