All posts by Bryna Parlow

Taste the Sights Around You?

I’m sure we’ve all seen the adorable puppies around campus in their purple vests. These are Susquehanna Service Dogs, and while some are training to be therapy dogs for hospital patients, some, after more training, will serve as seeing eye dogs. And while these animals can make an individual who is blind more independent, there is also been a technology developed can that can help blind and visually people “see” without using their eyes.

The idea for this actually stems back to the 1960’s, where Dr. Paul Bach-y-Rita was working on the idea of “sensory substation”- the concept that if you stimulate one sense, such as touch, it could take the place of another, such as sight.


(sorry that the photo is a little blurry, it was the only one I could find)

Back in 2009, neuroscientists from Wibcab. Inc. developed the pieces to put this apparatus together, known as a BrainPort. It starts with a small camera that is embedded in sunglasses worn by the user. The camera is connected, as you can see from the photo, to a “base unit” that the user holds in his/her hand. The main component of this base unit is a mini Central Processing Unit CPU), which is able to convert digital signals from the camera into electrical signals: this is what the retina does is someone who is not visually impaired. The base unit is also home to features such as adjustable shock intensity, zoom control, and light settings.

The electrical signals, once converted in base unit by the CPA, are sent to, you guessed it, the tongue (the pictures providing hint aplenty). On the tongue is a 3 cm by 3 cm arrangement of electrodes that contain a number of densely packed pixels. White pixels indicates a strong electrical signal, and black pixels indicate no signal.

What does it feel like to experience a “signal” on the tongue? The user describes it as “pop-rock” like feeling or champagne bubbles popping.

Here’s a closer look at what actually gets placed on the tongue.

This helps creates an “experience of vision” when the person stands and the camera send what’s there in front of them, in the most basic of spatial information, digitally to the base unit. The basic workings is this: if the person who has this device is standing in front of a dark hallway with a lights in the center, the electrical impulses will fire in the middle of the tongue.

If you’re thinking interpreting this information on the tongue might seem weird and hard to do, you’re right- at first. A neuroscientist from Wibcab, Aimee Arnoldnussen says, “It becomes a task of learning, no different than riding a bike…[the] process is similar to how a baby learns to see. Things may be strange at first, but over time they become familiar.”


So why use the tongue?

Surely there are larger surfaces on the human body where this pad can be placed, such as the back of the leg, or the stomach. The answer lies in the concentration of nerves in the tongue. One of my favorite parts of the Franklin Institute I remember is they had a table on pixel resolution.

The idea was you had a board with a few really large pegs so you really couldn’t tell the shape of your hand, a board with a more pegs so you could start to see it, and then finally a board with hundreds of really small pegs so you could see the ridges in each finger!


The tongue’s concentration of nerves is more like the picture on the right; they are more concentrated so when the electric signals fire those pixels they are able to create a more specific “picture.”

Another reason to use the tongue for the placement of this arrangement of electrodes is that the saliva produces in the mouth a great conductor for the electrical signals. This is a big advantage to using the tongue to other high densely-packed nerve area on the body, such as the fingertips.

There is hope for this technology to be used not just for people who are legally blind from birth, but also those that have suffered from glaucoma and macular degeneration.

One of the cool success stories has been for rock-climber Eric Weihenmayer, who completely lost his vision at age 13 due to retinoschisis, a condition where cysts form in the retinal tissue.

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Weihenmayer using the BrainPort device to climb an indoor rock wall.


An avid active person and climber before BrainPort, (he even has climbed Mt. Everest!) Weihenmayer describes using BrainPort as unique because he gets to experience “how to climb like a sighted person.”

All About that Context

We’ve seen a great deal of examples of illusions in Dr. Wyble’s lectures. The overwhelming majority of these were visual, like this beauty right here.


Knowing that items under a shadow appear darker, our brain compensates by making B appear lighter despite the fact that our eyes can perceive both squares as the same shade.


“Illusions” of context and framing effects plague the sensory world, so let’s explore a few instances of how context can affect sensory results.

Probably one of the best examples of this comes the following study description. In the study participants are given two sets of samples that are solutions of sodium chloride and water. One set, unknowingly to the participants deemed the “low” set, contains three samples at 12%, 18%, and 25% sodium. The “high” set contained three samples at 25%, 35%, and 50% sodium. After each sample they had to rate the taste on 1 to 7 Just About Right scale, with 1 meaning “very much not salty enough,” 4 meaning “Just about right,” and 7 meaning “very much too salty.”

Since the 25% solution was in both the high and low sets, you would think that participants would rate them both as the same intensity, right?


Turns out it is really dependent on the context of which the sample is presented in. It can make more sense when you look at the graph below.

sodium context
Notice how the Just About Right (JAR) scores are on the y axis, while NaCl concentration is on the x-axis. The box highlights how the same concentration of sample are rated different depending on which set they were presented in.

After tasting the 12% and 18% solutions, you can see how a person, after tasting the 25% sample, could rate that one towards a “too salty” rating. On the other hand, if the person happened to taste the 50% and the 35% samples before tasting the 25%, then the 25% sample would seem much less intense.

I helped run a similar lab with students taking the sensory class (FDSC 404) with sucrose/water solutions to help them see how context can really shape the ratings of samples.


Expectations also a play a huge role in perception. My boss last summer liked to use an example called “The Best Italian Restaurant in the World”. She would set up the scenario of you walking into this restaurant: the whole place smelled like Italian seasoning, there were red and white checkered table cloths, soft music played in the background. You sat down and then the waiter brought you your food: a roll of sushi. It wouldn’t matter if that sushi was some of the best sushi you ever had, the fact that you were expecting to be served delicious Italian food is going to impact how you perceive the sushi.

Timing is also another type of context effect. For example, let’s say creamery conducts an ice cream test to gather information about liking. However, they would get different results, on the same exact samples of ice cream, by simply changing the month the test was presented. Think about it….which would feel like a better time to enjoy some ice cream, January or July?

These effects can on some extent be compared to the confirmation bias examples we learned in class. All kinds of context effects can be out there. Sensory researchers know that they exist, so they must tread through experiment design carefully.

Concepts like the “halo effect,” which you may have learned about in an earlier psychology course, also exist in sensory. The halo effect describes the concept of how one positive attribute of a product can influence other, unrelated attributes of the same product is a positive direction. For example, thinking an attractive person must also be nice, good at sports, etc.

In this study, a couple drops of vanilla extract were added to samples of low-fat milk. Looking at the graph below, it would make sense that the perceived sweetness of the milk increased. However, the participants also rated the milk with the added vanilla as more creamy and thick, attributes that the added vanilla would not naturally affect whatsoever.

The asterisk above the column represent significant differences, so even though the vanilla would not effect the creaminess or thickness of the milk, participants rate them statistically higher than the control.

As fun as exploring the extent these context effects can be, knowledge about them is valuable for companies and researchers who are trying to achieve accurate and unbiased results.

One group that is good at avoiding context biases are groups that are used for Quantitative Descriptive Analysis. I remember at Smucker’s serving a lot of these types of panels. QDA is conducted by a panel that is trained using very specific food items. They go through hours of these trainings, basically learning how to rate certain items on the same scale. The cool thing about QDA is that because the group is so well attuned to each other while training, they work almost like a machine. For example, after being led through many sessions on chocolate frosting, every person in a QDA group can taste a sample of chocolate frosting individually and will all rate the frosting the same (for example, a 2.5 in creaminess on a scale from 1 to 5). You would ask questions about liking with QDA panel, but what’s cool is that (we’ll stick with the chocolate frosting example here) if you give them a frosting they’ve never tasted before, everyone in the group will still be able to give the frosting the same rating on the attributes they’ve trained for.

Nose Goes

We’ve all been there. We get a cold or the flu and dread the not-so-fun side effects that come along with it: headaches, stuffy and runny noses, and an overall general feeling of bleghh. It also dramatically effects how we taste food, aka it’s really hard. I think having a cold makes us realize how important our senses really are. As with moth most things, they’re something we take for granted and then miss it as soon as they’re gone.

So why is that, does being sick have a physical effect on our taste buds? Turns out the majority of the answer lies in our sense of smell!

There are two main routes by which odors get into the olfactory epithelium: orthonasally and retronasally. You are probably more familiar with orthonasal olfaction, which are odors that come straight through the nostrils from sniffing or inhalation. However, another overlooked part of how we “taste” foods comes from retronasal olfaction, which is when food releases volatile compounds in your mouth after chewing, swallowing, and/or exhalation. (It comes through the back of the nose, with retro meaning backwards).

You can see how the throat is connected to the naval cavity in the back, and that’s where the retronasal smells are detected, the back of the nose.


Remember, there are three main components that make up the flavor of a food: taste, smell, and texture. Most people don’t realize how much your sense of smell plays a role in detecting the flavor of food.

One simple experiment you can do to test this is also one of the initials labs done in the sensory class. Have your friend close their eyes give them a jellybean to eat. Make sure they pinch their nose closed before starting to chew, and have them identify the flavor. This should be a relatively hard thing to do, but have them un-pinch their noses mid-chew, and they should be able to get the flavor right.


This works because when the nose is pinched, we are essentially blocking off most of the air that can travel through the nose, including both orthonasal and retronasal smells. This is what having a cold can best be represented by. When we have a cold, our nose is often blocked my thick layers of extra mucus, limiting the amount of air that goes through the nose. This means that less odorants are binding to receptors in the olfactory epithelium, thus limiting how well we can smell.


Anosmia is defined as the inability to smell, and the condition can either be temporary or permanent. While its temporary when we have a cold, some people have what is called specific anosmia, which is the inability to detect a specific smell. I remember how my professor was telling the class how he had specific anosmia for pentadecalactone, which is a musky scent. He said it was especially hard because there was no way of knowing when it was in something.

Here’s a list of some smells and their rates of anosmia.


The differences in the rates can be attributed to genetics, which also affect not only what a person is able to smell but also the sensitivity of detection.

Things like a deviated septum can also cause anosmia and other causes have to do with physical damage to the nerve itself (and as you would imagine are more permanent). This includes injuries that cause damage to nasal-neuro pathways. In addition, the hypothalamus plays in a big role in smell memory, so damage to that may also effects one’s perception and memory of smells.

Fun fact: There are over 400 operative olfactory receptors, which enable us to be smell hundreds of different odors!

Check out this guide from the institute of Food Technologists on the basis of smell, which also gives a step-by-step guide similar to the jellybean experiment I outlined.

Another thing that is commonly mentioned when discussing smell is adaptation, or the process where one “gets used to” a smell so much so that they barely notice it or not notice it at all. This is a very good thing! Without adaptation, our receptors would send full-max intensity smells to our brain everywhere we went, which could get annoying and downright overwhelming if we were simply hanging out in a space that we knew really well, for example our rooms.


This picture, as the title states, shows a classic adaptation and recovery curve. It shows that over time a smell, given at the same intensity, will be perceived by us as less intense. However, when the smell is removed and then reintroduced (unfortunately the graph doesn’t numerical specify the amount of time), the perceived intensity of the smell comes back up.

Studies have been done that play around with this concept and releases from “mixture suppression.” This graph shows a study that was done giving people the same intensity of vanilla, cinnamon, and vanilla-cinnmon mixture smells. What they found was that after being given the vanilla smell, the participants rated the vanilla-cinnamon mixture as much higher in cinnamon, even though they were at equal intensities in the mixture!

mixture supression

So why does this happen? Perhaps it’s the way the brain is designed. Like how the eye is automatically drawn to things that stand out in a scene such as color and motion, maybe the smell receptors are designed to “pick out” the new smells we interact with.

I’m Not Picky- It’s Just (Possibly) Genetics

I don’t remember ever really identifying what cilantro was until I was in college. Before that, I never pinpointed why I hated certain salads or guacamoles. I found it had a weird, sort of soapy taste that I couldn’t trace to any particular item. I don’t know why it didn’t dawn on me to ask until college, but that’s when my roommate informed me those green flakes of off-flavored, soapy, bitter destruction was indeed cilantro and she didn’t think so  at all.

The fresh leaves of the oh-so-innconet-looking cilantro herb.

Cilantro is also called coriander and Chinese parsley in other parts of the world. It’s an annual herb and is from the carrot, parsnip, and celery family whose leaves contain several vitamins such as C, A, and K

After looking through some research, it’s found that cilantro is a very polarizing herb. Some work was done on simply asking 1400 young Canadian adults on their preference for cilantro and looking at their ethnic background. This University of Toronto study found that 21% of East Asians and 17% of Caucasians had an aversion to cilantro, while only 4% of Hispanics and 3% of Middle Eastern subjects had the same aversion. (It must be noted that the numbers of the different ethnicities interviewed are not equal. For example, there were 581 Caucasian people interviewed and only 27 Hispanic people).

This is the first step into looking for a genetic link. Because if people from similar backgrounds have the same aversion to a particular substance, then the next step would be to see of they all have something specific in their genes that it the “culprit” of sorts.


And lo and behold that’s where the science led. To further confirm a possible genetic link, a study was conducted during the early 2000’s in Twinsburg, OH at the Annual Twin festival. Researchers from the Sense Center of Philadelphia asked both fraternal and identical twins about their cilantro preferences. For 80% of the identical twins, they had the same preference for the herb. Only 50% of the fraternal twins interviewed had the same preference however. Since identical twins share 100% of their DNA and fraternal only 50% (just like any other siblings born to the same parents), there was further evidence to confirm a possible genetic link.

23andMe, a genetics company in California, analyzed genomes of around 30,000 people to see if their were specific genes that correlated with a like or dislike of cilantro. They asked these 30,000 people whether they liked or disliked cilantro and also what they thought it tasted like. Then gene analysis was done on the subjects that said cilantro tasted like soap. It was actually found that these subjects had a group of smell receptor genes that were similar, in particular OR6A2. OR2A6 is a gene that specifically encoded for the olfactory receptor that detects aldehydes.

It turns out when this gene is activated, it increase the sensitivity for the smell of aldehydes. Since both cilantro and soap contain a bunch of different aldehydes, this could be one reason for the link.

In addition the 23andMe study also found that 11.5% of Europeans who did not have the OR2A6 gene also reported a soapy taste. So as is the story with a lot of other things in this world- it’s complicated. Turns out there are multiple other genes that could also be the culprit, including one bitter-tasting receptor identified by Antti Knaapila and his team in 2012. It’s also important not to exclude environmental factors, such as growing up in a household that constantly east cilantro or none at all.

The cilantro-hating Julia Child

Even though more research needs to be conducted to determine all possible genetic links to cilantro aversion, my fellow cilantro-haters can live without fear of being called a “picky” eater, because how we have some genetics to back it up. Fun Fact: Julia Child, arguably one of the most famous chefs in the world, absolutely hated cilantro. When Larry King asked if she would eat a dish that contained cilantro, she replied “Never. I would pick it out if I saw it and throw it on the floor.”


Feelin’ Hot Hot Hot


Are you a seeker of spice? Does the idea of “burning” your tongue with the hottest pepper in the world appeal to you? According to Guinness World Records, the current hottest pepper in called the Carolina Reaper, which clocks in at 2.2 million Scoville Heat Units.

So, first things first…does eating a pepper actually burn your tongue?

The answer is no, well at least not in the same way as hot chocolate does.

When you burn your tongue by drinking a hot substance like coffee, physical damages is being done to the taste cells in the mouth. They can get scarred or burned quite easily, and you may have noticed you have trouble tasting and that your tongue/other part of the mouth feels rough within the burned area.

However, peppers have a different operational system for getting you to “feel” the heat.

Capsaicin (full scientific name: 8-methyl-N-vanillyl-trans-6-nonenamide), the molecule that is concentrated within the placental tissue of pepper (NOT the seeds, tell your friends that new fact of the day), is source of a chili pepper’s heat.

anatomy_of_a_ jalapeno
Notice how the capsaicin glands are located in the placental tissue.

What happened when you eat items containing chili pepper?

The capsaicin molecules activate the TRPV1 receptor in a chemical fashion, which signals an influx of Na+ and Ca 2+ ions into the cell. Coincidently, this receptor is also the same one that is triggered by intense heat or a physical abrasion. So, even though one feels the sensation of burning after eating a pepper, that’s all it is – a sensation. There’s no physical burning of tongue when eating a pepper (unless you heat that pepper in a microwave and put it immediately on your tongue of course).

The mechanism behind this “burning” sensation of capsaicin is studied through chemesthesis – the chemical mechanisms by which we feel burning, cooling, and even the bubbly feeling of carbonation of foods. These sorts of sensations are classified differently because they go through different nerves, specifically the trigeminal nerve. What also makes these sensations different from your basic tastes is the way we can become desensitized to them.

First look at the following chart, which shows you not only how powerful of an irritant capsaicin is, but also how long that feeling of irritation persists.

Capsaicin sensation of irritation lingers much longer than some other more common sensations from other foods.

One of the most common things studied with capsaicin is desensitization. Desensitization is the process by which you would rate something less intensely because of previous exposure to it. Experiments have showed that participants tasting a variety of capsaicin-infused samples show acute desensitization, with intervals between sample of 2.5-5 minutes and chronic desensitization, where they rate the intensity of the same sample over the course of days, with each subsequent day the intensity rating is, on average, less than before.

What’s also cool is that the intensity of the sensation is different based on exposure. Many studies have been done comparing the intensity ratings of capsaicin-fused samples from people who are frequent spicy food eater vs. people who rarely consume spicy foods.

Untitled 2
Notice how with both rinsing and sipping the spicy-food eaters (in red) still rate the capcaisin-infused sample as less intense than the non-consumers (in blue).

Yes, there is more to the Food Science Building than just the Creamery on the first floor. The second floor contains a variety of booths and other testing rooms where all kinds of food products and solutions are being tested. Companies and grad students alike test out their products to *paid* participants. I’ve worked in the sensory lab for about a year now, and in my time we’ve tested everything from ice cream to perogies to wine. We’re alway looking for new participants, so if you’re interested in being paid to try food, send an e-mail over to Jennifer Meengs, the coordinator of the Sensory Center, at

A cool experiment being conducted in the sensory food science lab here at Penn State involves the use of a capsaicin mouthwash given to non-spicy food eaters (using an intensity-matched bitter tasting mouthwash as the control). At the start of the experiment, they rate a whole bunch of different sample including sweet, salt, bitter, and yes, some that have capsaicin it them. After rinsing with the mouthwash twice every day they’ve come back to lab and again rated the same samples based on their intensity. The goal was to see the capsaicin-mouthwash participants rate samples of all the tastes, not just those with capsaicin, less intensely. The work so far is going well, and the lead researcher hopes that this work will be used to help patients with burning mouth syndrome become less sensitized.

Burning mouth syndrome is especially difficult to diagnose because the causes are most unknown. There are several “types” of burning mouth syndrome indented, with the first type having no known cause. Type II is often associated with anxiety, and Type III may be contributed by some allergies.


So if you remember in the last post we talked about the basic tastes, one of which was umami or “savory” which can best be described as the tastes of good ol’ monosodium glutamate (MSG).

Today, MSG is a flavor enhancer that can often be found in Chinese-style cooking and also a storm of controversy. Just a quick Internet search on MSG can garner stories from people suffering headaches, brain damage, and death – all attributed to MSG.

The molecular structure of MSG.

One of the more popular “attacks” on the substance is that people are attributing it to “Chinese Restaurant Syndrome.” In this syndrome, a person experiences headaches, heart palpitations, an increase in their asthma symptoms, and chest pain.

The “discovery” of this syndrome actually began in 1968, where the term was coined by Dr. Robert Ho Man Kwok in a letter to the New England Journal of Medicine. Though a Chinese immigrant himself, he said he only ever felt the syndrome when he was eating Chinese food in America, and described a number of the symptoms listed above along with the distinct ingredients in the foods he was eating, one of them being monosodium glutamate, The journal became flooded with responses of readers sharing their own stories, and it was even picked up by The New York Times. A study was done in 1969 that injected large amounts of MSG in mice that ignited a firestorm of fear and panic because of the neurological effects on the mice.

 After that point, countless studies have been done on the effects of MSG. It’s been given to patients orally and intravenously, in small does and extremely high doses, to mice and humans, etc.


But let’s take a step back to figure out what we know. Monosodium glutamate is a derivative of glutamate, which we learned is an important neurotransmitter in the body. It’s an excitatory transmitter, which means its presence will cause an increase in the frequency of its nerve impulse when its being sent. Therefore an increase in heart rate wouldn’t be surprising as a potential side effect of MSG.

A lot of studies have reported that headaches increase with the consumption of MSG. A study done in 2009 by Jennifer Xiong showed that neural damage in the brain was dose dependent for MSG, meaning the higher the dose given, the more damage there was to the mature neurons. Though Xiong did not find the exact mechanism, this is what was determined to be the cause of the headaches. However, it was also found that MSG did not cause damage to glial cells or immature neurons, and the presence of Vitamin C also helped decrease the headache effects of MSG.

One of the figures from the Xiong study. Notice how the neurons swell from their original size with the introduction of MSG.

An important thing to consider hear is the blood brain barrier, which has a low permeability to MSG. This is especially true to dietary MSG (foods naturally present with MSG, like tomatoes, vs. just being added in), so the actual amount of extra glutamate getting into your brain is small. Another thing to consider here is the actual amount of MSG an average person consumes in a day. The average dose for a person in the U.S is 0.55 g/day, but a large meal at a Chinese restaurant could have up to 3 grams, making the possibility of headaches and other symptoms more likely.


So what’s the verdict? Based on numerous studies, evidence of MSG sensitivity is a proven concept. Though the extent of symptoms is based on the sensitivity of the person, it takes a relatively large amount for effects to be felt. So, MSG is regarded as safe in regular amounts, but could have unpleasant when eaten in excessive amounts.

There is so much data on this topic, so it’s easy to see why people are very adamant about MSG. In one single article I read it listed various symptoms of “Chinese Restaurant Syndrome” and then gave links to studies where it was both proven and disproven for every symptom.