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Eating in Front of a Mirror Can Make Junk Food Less Delicious

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Nutrition science is a complicated, ever-changing animal. Some experts believe fat is the enemy, while others suggest eating more of it. The same is true for carbs, alcohol, and caffeine. It’s hard to know what’s healthy and what’s not, although there are some exceptions. A cheeseburger, for example. A piece of chocolate cake. A bag of potato chips. A bowl of ice cream. We eat these foods knowing that they’re not good for us. Now, one researcher says that recognizing that guilt can actually ruin the taste of the food.

Behavioral scientists have something called the objective self-awareness theory, which basically says that seeing yourself—whether physically in a mirror or photograph or mentally through writing—forces you to think about what you're doing and why. Studies have shown that this heightened self-awareness can actually change behavior. People confronted with their own image are less likely to cheat on tests, act on sexual impulses, and stereotype other people.

Marketing expert Ata Jami wondered if raising people’s self-awareness could change the way they ate. Would eating junk food be less enjoyable for people who had to watch themselves do it?

Jami ran four experiments on hundreds of undergraduate volunteers at the University of Utah. All the volunteers were told they would be taste-testing new products. 

In the first study, participants were offered a choice between two chocolate bars: one described as “healthy” and the other as “tasty.” They were then left alone in a room with or without a mirror to taste the chocolate. After they finished the chocolate, the volunteers filled out a survey rating the chocolate’s taste. People who had picked the “tasty” chocolate didn’t like it very much—but only when they had to eat it in front of a mirror. Volunteers who sat in rooms without mirrors rated the unhealthy chocolate bar just fine. And mirror or no mirror, the “healthy” chocolate got high marks from every taster.

The second and third studies focused on responsibility. Some study participants were randomly assigned to taste either brownies or dried fruit. Others were told to rank a list of healthy and unhealthy snacks in order of their preference. Then they were randomly assigned brownies or dried fruit anyway, with a cover story that the experimenters had “run out” of the other choices. Some people had ranked brownies or dried fruit highly and actually got what they wanted. Everybody else just ate what they were given.

Choice proved to be an important element. People in mirrored rooms who chose to eat brownies gave the brownies a low grade. But everything tasted just fine to the taste-testers who had asked for something else. In short, people who had to watch themselves eat only disliked eating brownies when it had been their idea in the first place. 

Jami has a theory about why the taste of junk food suffers. In an upcoming paper in the Journal of the Association for Consumer Research, he explains that awareness of our poor choices makes us uncomfortable. In the absence of any obvious cause for the discomfort, he says, we tend to blame whatever’s in front of us. In the first three experiments, study participants had been told to pay attention to how the food tasted. It's only natural that the unpleasant feelings manifested as flavor issues.

To test this idea, he added one more element to the last study: music. Study participants were divided into two groups. Jami piped music into all of the study rooms. Half of the volunteers proceeded as usual with the mirrored taste tests. The other half were told that the experiment was trying to test whether or not music could affect their feelings. All participants got to choose between chocolate cake and fruit salad.

The results for the first group matched those of the other three studies: mirror + junk food = ick. People who ate healthy food thought their food tasted fine, as did people who ate junk food without a mirror. But people in the second group had been primed to pay special attention to the music. Sure enough, volunteers in the mirror/music/cake group rated their cake as perfectly tasty. Jami believes they attributed their unease to the music instead. 

Now, there are a few caveats to consider before we conclude that adding mirrors to our dining rooms will make us all thin. First, Jami didn’t measure how much people ate. He just measured how bad it made them feel. For all we know, that uneasy feeling could prompt us to eat more.

Secondly, “healthy” and “unhealthy” are kind of fluid terms, especially in this study. For example, the “healthy” and “tasty” chocolate bars in the first experiment? Those were all the same chocolate bars. The experimenters just called them different things. So it’s not necessarily that eating unhealthy food makes us uncomfortable—it’s eating food we think is unhealthy.

Lastly, Jami is not sure how it will work with actual meals, since people often eat healthy and unhealthy food together. If dinner is a cheeseburger and a salad, does the mirror make only the cheeseburger taste bad? Does the salad also take a hit? Do they both taste fine? Nobody knows.

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Researchers Pore Over the Physics Behind the Layered Latte
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The layered latte isn't the most widely known espresso drink on coffee-shop menus, but it is a scientific curiosity. Instead of a traditional latte, where steamed milk is poured into a shot (or several) of espresso, the layered latte is made by pouring the espresso into a glass of hot milk. The result is an Instagram-friendly drink that features a gradient of milky coffee colors from pure white on the bottom to dark brown on the top. The effect is odd enough that Princeton University researchers decided to explore the fluid dynamics that make it happen, as The New York Times reports.

In a new study in Nature Communications, Princeton engineering professor Howard Stone and his team explore just what creates the distinct horizontal layers pattern of layered latte. To find out, they injected warm, dyed water into a tank filled with warm salt water, mimicking the process of pouring low-density espresso into higher-density steamed milk.

Four different images of a latte forming layers over time
Xue et al., Nature Communications (2017)

According to the study, the layered look of the latte forms over the course of minutes, and can last for "tens of minutes, or even several hours" if the drink isn't stirred. When the espresso-like dyed water was injected into the salt brine, the downward jet of the dyed water floated up to the top of the tank, because the buoyant force of the low-density liquid encountering the higher-density brine forced it upward. The layers become more visible when the hot drink cools down.

The New York Times explains it succinctly:

When the liquids try to mix, layered patterns form as gradients in temperature cause a portion of the liquid to heat up, become lighter and rise, while another, denser portion sinks. This gives rise to convection cells that trap mixtures of similar densities within layers.

This structure can withstand gentle movement, such as a light stirring or sipping, and can stay stable for as long as a day or more. The layers don't disappear until the liquids cool down to room temperature.

But before you go trying to experiment with layering your own lattes, know that it can be trickier than the study—which refers to the process as "haphazardly pouring espresso into a glass of warm milk"—makes it sound. You may need to experiment several times with the speed and height of your pour and the ratio of espresso to milk before you get the look just right.

[h/t The New York Times]

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Why Some Cold Cuts Make Iridescent Meat Rainbows—and Why They're Still OK to Eat
Kirill Ignatyev, Flickr // CC BY-NC 2.0
Kirill Ignatyev, Flickr // CC BY-NC 2.0

We eat with our eyes first, and sometimes what we see on our plate turns us off a meal altogether. Take so-called “meat rainbows”: They happen when a slice of deli meat takes on an iridescent shimmer reminiscent of an oil puddle in a parking lot—a.k.a. not something you want on your sandwich. Despite giving a whole new meaning to the phrase "mystery meat," the odd discoloration is perfectly safe to eat, as physicist Dave McCowan at the University of Chicago explained for The Takeout.

The colorful sheen on a slice of roast beef or pastrami isn’t a sign of spoilage or chemical additives—it’s actually a result of the way the meat is cut. Slicing meat “against the grain” means cutting through, rather than parallel to, the bundles of fibers composing the meat’s musculature. This makes for a more tender bite, and it also leaves a grid of evenly-spaced meat fibers. In the right light, this surface lends itself to something called “diffraction.”

Diffraction occurs when light hits a repeating pattern of nooks and crannies. As the white light bounces off the grooves in the meat, it separates into a spectrum of distinct colors. Some of these colors are amplified, creating a mother-of-pearl appearance when viewed together. This is the same effect we see on the backs of CDs and DVDs.

Another possible culprit behind your rainbow meat is thin-film interference. This is sometimes present in meat with a thin layer of oily fat on the surface. The film affects the light passing through it in such a way that only some of the colors in the spectrum come through, hence the rainbow. This phenomenon produces a sheen closer to that of bubbles or oil slicks than laser discs.

Why do meat rainbows only seem to show up in deli slices, not raw cuts? The answer lies in the curing process. A cured ham is likely greasier than a raw pork cutlet, which makes thin-film interference more likely. The muscle fibers in cured and cooked meats are also more tightly packed together, producing the rigid grid necessary for diffraction.

Color also plays a role. Iridescent shimmers are easier to spot on darker meats like beef and some pork—so if you’re eating a slice of turkey from the deli, it could be covered in meat rainbows you don’t notice. We’ll let you decide if that’s a positive thing.

[h/t The Takeout]

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