Face Metamorphs

In Harry Potter and the Order of the Phoenix, readers are introduced to Nymphadora Tonks, one of the aurors sent to help Harry get from Privet Drive to Grimmauld Place. Tonks is a metamorphmagus, presumably meaning a mage or magic-user who can metamorphose. Tonks describes her skill as being able to “change her appearance at will”. She is born with the ability, unlike other magic-users who “typically need a wand or a potion”. The relevant potion is used throughout the series: Polyjuice. (I’ve made use of it in a Potions project for one of my classes.) The wand might refer to a disfiguring spell that Hermione casts on Harry in Deathly Hallows as the trio are about to be captured by Snatchers.

The Polyjuice potion, we are told, is temporary; a dose lasts an hour according to Chamber of Secrets. It’s unclear how long Hermione’s spell lasts. Harry certainly wonders how temporary it is as he tries to pass off as a Slytherin, thanks to his knowledge of the common room when he used Polyjuice in his second year at Hogwarts. While Polyjuice transforms the drinker entirely into the person who owned the hair (presumably as a DNA source) that is added to the potion, the extent of Hermione’s spell is less clear. It certainly affected Harry’s facial features significantly; everyone else has trouble recognizing him. The spell must wear off after some time, since everyone seems to recognize him normally after the incident at Malfoy Manor. As for Tonks’ ability, the books mainly describe changes she makes to her face simply by physically willing the transformation with mental (and presumably magical) concentration. She doesn’t seem to have trouble maintaining any disguises.

Okay, I’ve talked about the magic. Regular readers of my blog can anticipate the next question: Where does the science come in?

In Chapter 8 of Do Zombies Dream of Undead Sheep, written by a pair of neuroscientists, the subject of facial recognition (or lack thereof by zombies) is discussed. Here’s what I learned. There are two types of clinical disorders related to facial recognition problems. One is psychiatric and known as Capgrass delusion, where you think that someone you know has been “replaced by an impostor”; how and why it arises is unclear. The other is neurological and known as prosopagnosia (combining the Greek words for “face” and “not knowing”), and closely related to it is prosopometamorphosia – perceiving a “visual distortion of facial features”. The latter can also be induced by electromagnetically stimulating the fusiform gyrus in the brain.

The system that recognizes faces, part of the ventral visual stream, turns out to be quite complex. The authors of Zombies refer to it as the “face network”; multiple areas of the brain light up in an fMRI scan, more so than for many other perceptual activities. But is it more complex to disguise yourself by physically transforming your face instead of affecting the perceptions of those around you? From an energy-counting perspective, perhaps the latter. If magic is conducted via electromagnetic radiation, then releasing the appropriate photons (via magical means) to affect other humans within a nearby radius might be energetically less complicated than physically altering your biology: changing bone, skin, and other facial features. The Harry Potter books implicitly assume the physical changes to oneself rather than perceptual affectation of others, but there’s also the Obliviate charm akin to a nifty memory-altering device used in the Men in Black movies. A Confundus might also work.

All this is to say that we should learn more science to have more powerful magic!