The Chemistry of Christmas

What are the sights, the sounds, the smells, and the textures that you associate with Christmas? Perhaps it is Christmas trees with their lovely green shape, color and wonderful pine smell. Maybe it’s the smells of cooking, the savory smells of turkey or the sweet smell of warm cookies. Or what about all of the cozy feelings you get with big sweaters or a roaring fire? Did you know that there is a lot of chemistry that goes into all of the senses we associate with this holiday?

I was browsing through holiday-related articles, looking for something different from the usual psychology or sociology centered holiday study. That’s when I came across an article from 2012 published in the Journal of Chemical Education about the five senses of Christmas chemistry. The authors look through the lens of organic chemistry and take five “Christmas compounds” to examine in the context of the five senses.

Sound: Silver Fulminate

In 1824, Justus Liebig correctly determined the molecular formula of silver fulminate (AgCNO), and, around the same time, Friedrich Wohler identified the molecular formula for silver cyanate (AgOCN). Now, these might look the same, but they are in fact very different. Soon after, these scientists collaborated and rationalized these differences by introducing the notion of isomerism – molecules that have the same kinds of atoms but because these atoms have different arrangements in shape they differ in their chemical and physical properties. Silver fulminate is highly unstable, and even a small amount of friction leads to its violent decomposition. That makes it very useful when you want to make things go boom.

Christmas crackers are items that are a more traditional favorite in the UK. The Christmas crackers used today are short cardboard tubes wrapped in colorful paper. When they are pulled – bang! – out comes a colorful hat (usually looking like a crown), a small toy or a joke. The sound is made from the rapid breakdown of silver fulminate present in small quantities in the paper. Two thin strips of cardboard are glued together, one containing silver fulminate and the other a rough surface. When the cracker is pulled, the surfaces rub together to produce friction and facilitate the reaction. The compound goes through a redox reaction followed by a release of nitrogen gas and carbon monoxide. This sudden production of gases is what produces the distinctive popping sounds.

Sight: α-pinene

A beautifully lit and decorated Christmas tree is one of the most common sights of this holiday. For the purposes of this section, we’ll assume that you bought a real tree rather than an artificial one. Geographic region can play a big part in the species of tree that is available to you, but they are very likely all evergreens (fir, spruce, pine, and cedars). In their resin, these conifers release terpene hydrocarbons, specifically monoterpenoids that is composed of two isoprene building blocks. This word should sound familiar as it is a derivative of turpentine, which you may know for its distinctive pine scent. Pine oil contains two monoterpenoids, α-pinene and β-pinene, which are both liquid at room temperature. This is another case of isomerism; although both have the typical C10H16 molecular formula there are four stereoisomers of each where the bonded atoms differing in their 3-D orientations. α-pinene is one of the most common volatiles in nature and is directly linked to the Christmas tree’s smell.

Touch: Sodium Acetate 

I don’t live in what most people would term a cold climate. Sure, we get cold weather, but we’re not talking blizzards. However, in my days as a field ecologist I spent many a winter day outside taking measurements. On those days, I was ever-so-grateful for one little invention: the hand warmer. Squish around the contents of the packet to get it to heat up to keep your pockets, and hands, toasty all day long. Bliss.

Many hand warmers are based on a simple chemical reaction – the crystallization of a supersaturated sodium acetate solution. When you squish around the contents of the hand warmer, you are triggering a chemical process. A nucleation site, usually a metal disk with small seed crystals, causes rapid crystallization of the super saturated solution. This is a highly exothermic process that releases energy to its surroundings as heat. These types of hand warmers are often reusable because of their physical mode of action. Other hand warmers rely on the exothermic oxidation of iron when exposed to air. Activated charcoal is used to catalyze the reaction, along with vermiculite and salt as additives. However, this chemical mode of action means that these are one use only products.

Taste: Tryptophan

If you are a fan of a big turkey dinner then you have probably heard of tryptophan. It is a common misconception that the tryptophan from your turkey binge brings on sleepiness. It’s true that tryptophan is involved in sleep and mood control. However, turkey doesn’t contain enough of the compound (only 350 mg per 115 g) to have a soporific effect. It’s more likely that the sheer volume of food that you eat (and probably the wine you drank with it) on these occasions decreases blood flow and oxygenation, inducing the drowsiness.

Tryptophan is an essential aromatic amino acid that is commonly found in proteins. This compound has two enantiomers, chiral molecules that are mirror images of one another (kinda like left and right hands). L-tryptophan exists in nature and has a pronounced bitter taste, while D-tryptophan is synthetic and has a very sweet taste. Once you consume tryptophan, it goes through a series of metabolic reactions, one of which ends with melatonin. This final product is a neurohormone that is naturally secreted by the pineal gland, is involved in regulating circadian rhythms and may also have strong antioxidant effects.

Smell: Gingerol

Gingersnap cookies and gingerbread houses are common sights around the holidays, and with them come their wonderful ginger scent. Ginger products usually contain fresh or powdered bits from the rhizomes (rootstalk, or modified underground stem) of the ginger plant (Zingiber officinale). One of the organic compounds produced by this plant is gingerol, an aromatic vanilloid compound containing a β-hydroxyketone functionality. Interestingly, the taste of this compound can be modified via laboratory synthesis. Shogaol is derived by either refluxing gingerol with concentrated sulfuric acid or allowing a dehydration reaction can occur on gingerol to give the aldol condensation product. Shogaol has a more pungent flavor than gingerol. Conversely, ginergol can completely break down into zingerone after refluxing in strong aqueous base. Zingerone is considered to have less pungency than gingerol.

Considering this chemistry, you can alter the flavor of the ginger you use in your cooking. For example, if you cook ginger extensively, particularly in the absence of acid, then you produce the mildest tasting vanilloids, zingerone. But also keep in mind that your kitchen conditions are not laboratory conditions. This means that you are likely to end up with a mixture of all three compounds in your cookies.


That’s all for our journey through the senses of Christmas. If you are a chemistry teacher, or simply a chemistry nut, then I recommend reading through the paper. It has all sorts of skeletal formulas that you’ll love.


Jackson, D., & Dicks, A. (2012). The Five Senses of Christmas Chemistry Journal of Chemical Education, 89 (10), 1267-1273 DOI: 10.1021/ed300231z


p.s. In the interest of equal opportunity holiday science, does anyone recommend a study on Hanukka, Kwanzaa, etc. My academic database search is coming up with nil.



(images via Science Notes, Old English Crackers, Buzzle, ThinkGeek, NYTimes Blogs, spydersen, respectively)

Phylogenetic Christmas Tree

hmmmm...I should do this...

(via xkcd)

The White Elephant in the Room: The Gift of Subversion

Ah, the holiday work party. Free food, spending time with people you spend your whole day with already, and enough boozy libations to make things a bit more interesting. Here in North America, many workplaces engage in the gift “game” called the White Elephant Gift Exchange. On this topic, I'm basing today’s post on an article that I recently came across by Gretchen Herrmann in The Journal of Popular Culture where she dissects the Machiavellian nature of this little holiday game.

The White Elephant Gift Exchange (that I’ll abbreviate to WEGE, which you are free to pronounce as ‘wedgie’ even though no one does) is a pastime aimed to upend our normal conventions and beliefs of holiday generosity by celebrating and subverting the materialism. The goal is an unleashing of entertainment and satire, made all that much better after the first glass or two of eggnog.

I've written before on the topic of the perfect gift, concluding that considering someone’s interests and getting them something that you know they will love and use is the way to go. Herrmann generally agrees on this conclusion, pointing out that the ideal gift is a special item that is imbued with personal sentiment. This special item carries with it an emotional attachment that transcends the obligatory reciprocity of typical gift-giving. But object of the WEGE is exactly the opposite of all of that.

Actually, the name WEGE can vary depending on the type of gifts. The specific version of the game typically goes after a particular brand of holiday subversion: shrewd trading and parsimony (e.g., Yankee Swap, Scotch Auction), undercutting holiday beneficence (e.g., Dirty Santa, Evil Santa), turning Christmas on its head by those that are considered inscrutable and untrustworthy (e.g., Chinese Christmas, Chinese Gift Exchange), pointing to the dubious value of the gift or that it might be pre-owned (e.g., WEGE), and/or telegraphing personal gain at the expense of others (e.g., Stealing Santa, Rob Your Neighbor, Cut Throat Christmas).

Basically, the rules are these:

1. Participants bring an anonymous wrapped gift that fits within prespecified guidelines (price, regifting, etc.) that they slip into the gift pile. 
2. Everyone picks a number that is used to determine the gift-choosing order of the participants. 
3. First Turn: The first person called chooses a gift from the pile, opens it, and then displays it to the other participants. 
4. Second Turn: The next person has three choices. They can either a) steal the gift from the first person, sending them back to the gift pile for another, b) select, unwrap and keep a gift from the pile, or c) select and unwrap a gift from the pile and swap the unwanted gift with the first person. 
5. All Subsequent Turns: Each new person can steal any unwrapped gift or choose a wrapped gift from the pile. However, a gift can’t be stolen more than once during a turn, and a particular gift can’t be immediately stolen back from the participant who just stole it.

WEGE it isn’t about the personalization, it’s about the stealing. The Machiavellian nature of the game is spelled out in its stealing, its taking, its greed. Rather than the generosity of the personalized, perfect gift, the emphasis is placed on personal gain, creating a series of winners and losers, and getting something for nothing with impunity at the expense of another. I think we can all agree that that is what makes it fun.

You want to make sure that you bring a gift that will engender group favor and can trigger a chain reaction of stealing and hilarity. For example, one of the most popular gifts I’ve seen at one of these events was a big battle axe. Yeah, a real one. How many times it was stolen = funny; who actually wanted a battle axe for their very own = hilarious. In other years, the same group went crazy over gifts like a big stuffed moose or a case of craft beer (I ended up with that one!). So is there a key to picking out the perfect gift for one of these events?

First is to consider your group. Do they appreciate the tacky, silly, and weird or are they more the classy, mainstream crowd? However, slipping a bizarre gift into the latter crowd’s pile will likely cause unexpected amusement. Second is to keep to those prespecified rules. Don’t spend a lot of money trying to impress people; keeping to the anonymity means they won’t know it was you anyway. Next is to not forget the creative wrapping and use it to satirize as well – although you might have to be equally creative to keep it anonymous as you walk into the party.

Herrmann explores the transient nature of both the receiving of the gift and your attachment to it. In the game, the gift itself can be arbitrary and that participants are forced to focus on the transience of possession instead. She cites behavioral economists who describe the “endowment effect,” wherein the brief possession of an item makes it worth more to the owner than other identical items. This extra value makes the stealing of this item even that much more poignant. However, she also points out what we’ve all heard during particularly rousing games: “Give me that! I want it!” so there is at least some value of the item too.

Herrmann breaks down the gifts into three categories:

Fetishized Commodities: Those items that are disproportionately coveted and stolen. My battle axe example is a good one. These gifts take on a life of their own as they gain more value every time they are stolen. A hierarchy of items can emerge as the game goes on. Within this hierarchy are also a series of substrategies like pointing out other gifts to take attention away from yours, loudly hawking lousy gifts in the hopes of trading up, sitting low and hopping no one will see and remember what you have, or even making after-game deals.

Booby Prizes: Of course, no one wants to end up with the “booby prize” or gifts at the undesirable end of the hierarchy. So much so that often the rules will stipulate that the final recipient must take it home with them. It can sometimes be difficult to predict whether a gift will be seen as a booby prize. Perhaps the battle axe was originally meant as a booby prize, a way offload an old D&D costume. But bad became good.

Lazarus Gifts: These are the items that make reappearances in coming years. They are the ones that are most commented on, laughed about, or pawned off. These resurrected gifts actually add to the layers of complexity and amusement of the WEGE.

Ultimately, the WEGE is about group bonding through entertainment. Perhaps that’s why it is so often played at workplace parties. There’s a ritualistic swapping of gifts, but you don’t need to go through the stress of finding the perfect gift. So this year, think of a creative, subversive, fun WEGE gift. Oh yeah, and don’t forget to steal all those good ones away too!


M. Herrmann, G. (2013). Machiavelli Meets Christmas: The White Elephant Gift Exchange and the Holiday Spirit The Journal of Popular Culture, 46 (6), 1310-1329 DOI: 10.1111/jpcu.12090



(image via The Lovely Journeys)

Scientifically Accurate Santa

The trend of turning your favorite characters, icons, and historical figures into their scientifically accurate (and often rather crude) versions continues with Scientifically Accurate Santa.

Merry Christmas (or other applicable holiday)!

The Gift of Regifting

Be honest: How bad is it to regift? We've all gotten gifts that are clearly items someone was given and didn't want. A Chia Pet, a fruitcake, or an ugly piece of jewelry. Some things you can just tell. No lie, I once got a set of used cassette tapes. I don't even own a cassette tape player. I considered rethinking a friendship.

Most often, people regift things they will not use or gifts they do not like. If you want to stick a name on it, it is a problem researchers refer to as "deadweight loss." This is because the gift recipients would never spend as much money as the giver (especially on an ugly, unusable item like that), and the receiver is left with an item that lingers around in the closet (or wherever) until they can get rid of it (hence, the "deadweight" terminology). How do you shed the deadweight? You pass it on. Maybe the receiver will appreciate it in ways you never did, or at least they will pretend to. And this gets to the heart of today's post: How do people regard regifting? Resourceful and thrifty or rude and distasteful? Does it matter if you are the giver or the receiver? A study published this year in Psychological Science asked just these questions in a series of studies.

Study 1: Is it okay to regift gift cards?
Participants were asked to imagine that a 50 dollar Amazon gift card had been given as a birthday gift and then regifted to someone else. Then they were asked to assess their feelings as either the giver or the regifter. The researchers found that regifters thought the giver would be more offended if they regifted the card than givers reported that feeling.

Study 2: Do you regift or throw away an undesirable present?
The first study showed that regifters may be overestimating how offended the givers would be at having their present regifted. But what if that present were just thrown away? Participants were asked to imagine that they had recently given or received a wristwatch as a gift and, depending on the rolls they were assigned (giver or receiver), how would they feel if the watch was either regifted or thrown away? Similar to Study 1, the researchers found that the receivers thought that regifting or throwing a gift away would offend givers more than givers felt they would have been offended. They also found that the recipients found throwing away a gift to be more offensive than regifting it. Givers were less offended if their present was regifted than if it was thrown away.

Study 3: In the real world, how do friends really feel about regifting?
In this study, the researchers wanted to get a more real world feel. How do real groups of friends feel about regifting? So they asked participants to sign up with two of their friends. One member of this group was assigned the roll of the giver, separated from the group, and asked to choose from three items that were pretested and identified as bad gifts (a magazine for retired people, a DVD about the life of Mandy Moore, and a weight-loss cookbook). The giver then wrapped their gift and gave it to one of their friends. Once the giver had gone back to the waiting room, the receiver (now the regifter) of the bad gift was then asked to rewrap the bad gift. Then, in front of the initial giver, the regifter enters the waiting room with the rewrapped gift and gives it to the final friend. I don't know about you, but this almost sounds mean just reading it. When each was asked about their feelings on this bout of regifting, the regivers again thought the initial giver would be more offended than they were. Givers thought that the regifters were entitled to do what they wished with the gift.

Study 4: Is it possible to make receivers more comfortable with regifting?
Did you know that there is a National Regifting Day? It's true. In honor of holiday office parties and the “unique” gifts exchanged at them, the creators of Regiftable.com have declared the third Thursday in December as National Regifting Day. The results of Study 3 suggested that interventions that encourage receivers to do what they wish with their gifts may liberate them to regift. The researchers found that study participants were more likely to regift if they were told that it was National Regifting Day than if they were not told. They also found that receivers felt more entitled to do what they wanted with their bad gift if they were told it was National Regifting Day, although they still felt less entitled than givers thought they should.

When I stop and think about it, this all makes sense. However, I maintain that giving a bad gift (like used cassette tapes) is still giving a bad gift and that isn't being a good friend or relative. Go back and read the last gift giving post, your friends often don't need something flashy or weird (unless they are that kind of personality). Think about what they want and get it for them. Odds are that they will keep your gift and use it. At least I hope so. And if not, this article suggests that they don't mind if you regift it. I would have been interested to see another choice in Study 2 that included feelings on donating the gift.

What about you? What are your thoughts on regifting? Will you be giving away that ugly office gift from last year?

Adams, G., Flynn, F., & Norton, M. (2012). The Gifts We Keep on Giving: Documenting and Destigmatizing the Regifting Taboo Psychological Science, 23 (10), 1145-1150 DOI: 10.1177/0956797612439718

Some more regifting reading:
The New York Times: "Re-Gifting: You Shouldn’t Have. But if You Did, Here’s How to Get Away With It"
The Huffington Post: "To Regift or Not to Regift, That Is the Question" and "Regifting Christmas Presents: How To Do It Properly"
ABC News: "Re-Gifting: It’s Not Just for the Poor, Frugal or Unashamed Anymore"

The Psychology of Gift Giving: Unique and Expensive or Ordinary but Useful?

The holiday shopping season is almost upon us. Black Friday is but a couple of days away. The annual shopping explosion event when you start thinking how close the year is to being over, how you haven’t even thought about what you are going to buy anyone, and how much money you don’t have to spend. Actually, I tend to be a Cyber Monday kind of shopper, but the same tenets hold true.

Gift giving: What do you get someone? Will they like it? What will they give you? Will you like it? Quite frankly, the whole process can be fun but exhausting.

Gifts can be tokens of social relationships, ways that we transmit impressions and feelings to one another. If you boil down the above questions, you are really asking about the attractiveness of gifts. A study in 2005 looked at the attractiveness of a gift seen from the perspective of the giver and the recipient. When you are shopping and picking out a gift, you probably go for something that you find attractive and/or you think the receiver will find attractive. Ultimately, you want your gift exchange to be successful. As a giver, that means you try to take the receiver’s perspective into account. As a recipient, that means you realize that any number of gifts could have been chosen for you and the one you received is what the giver thought you would like best. As with so many social psychology papers, this question of gift attractiveness was broken down into a series of studies.

Study 1: High-quality and unique or ordinary but useful? 
Ideally, you want to choose a gift that is both high-quality but also useful to the recipient. But high-quality usually means expensive. If, as a giver, your shopping list doesn’t include expensive then you have to make a trade-off. Usually this means a smaller, high-quality gift or a larger, more ordinary gift. This first type of gift is nice, and often exclusive or unique. The second type of gift is probably something more useful, something the recipient can use. They found that givers preferred to give expensive, exclusive, smaller gifts. On the other hand, receivers preferred less luxurious, more useful gifts. Makes sense I guess. As a giver, you want to give someone something both you and they perceive as nice. As a receiver, you actually have to live with that gift.

Study 2: What do you expect of your gifts? 
Cultural conventions, we all fall into them. In western societies, a gift should be nicely wrapped, come without a price tag, and arrive on time. The gift itself should be neither too cheap nor too expensive (especially as gifts are often reciprocal). Oh, and cash is only accepted under certain circumstances, usually helping someone pay for something specific (house, car, school, etc.). Receivers are expected to act surprised when they open the gift (even if they knew what it is), to be grateful, and to praise the gift (even when they hate it). This study asked people a series of questions: Gift voucher (gift cards) or cash? Opera or movie tickets? How important is it that a gift be a surprise? Or arrive on time? They found that givers prefer gift vouchers to cash and are concerned about timing, showing that gift givers are more serious about social conventions than are recipients. It’s weird really, because they found that gift givers are most concerned with pleasing the receiver even though the givers are abiding by cultural conventions that don’t do that (see Study 1). Receivers accept cash gifts and claim to not really care if the gift arrives late.

Study 3: Does self-perception or perceptions of others play into gift giving? 
Personally, you prefer the ordinary but useful gift, but you think these preferences are not shared by others. So you end up selecting gifts according to the preferences you think are more widespread among others. "Everybody likes expensive wine so I will buy expensive wine as a gift." They found little support for this self versus others perception hypothesis. Rather, people change their preferences in accordance with their rolls as either givers or receivers.

Study 4: Why are some conventions more important than others? 
It is nice to divide these questions up into studies, but in real life, pairwise comparisons aren’t made. When choosing a gift, givers have to choose between two or more simultaneous options and evaluate potential gifts one by one. Receivers don’t know all of the decision-making that the givers went through to pick their gift or what other gifts they could have gotten instead. This study found that when receivers evaluate a gift on its own they tend to agree with the givers’ preferences and prefer more exclusive gifts.

So what do we take away from a paper like this? Studies 1 – 3 seem to say “Skip the fancy wine and just buy them the comfy sweater.” I tend to agree. Buy something you know they will both love and use. Look at cultural gift giving conventions and choose to step away and consider your friend or loved one’s interests.

Our next topic – Regifiting…you know you shouldn’t but is it really the taboo you think it is?


Teigen, K., Olsen, M., & Solås, O. (2005). Giver-receiver asymmetries in gift preferences British Journal of Social Psychology, 44 (1), 125-144 DOI: 10.1348/014466604X23428


Read more about gift giving:
Scientific American: "The Psychology Behind Gift-Giving and Generosity"
NY Times: "A Gift That Gives Right Back? The Giving Itself"


(image via MoneyIntention.com)