Researcher Taylor Webb sets up a TMS experiment with Branden Bio, a first year grad student in psychology and neuroscience.
Researcher Taylor Webb sets up a TMS experiment with Branden Bio, a first year grad student in psychology and neuroscience.

‘Have you done this before?” the woman asks. “I have,” I answer, as I sign the last consent form. “Have I ever been injured by a metallic object or shrapnel?” No. Have I ever done metal work like welding?” No. “Do I have a pacemaker?” It goes on. The lengthy form lists every imaginable reason that one could have metal in the body. I check “no” for each question. I remove my shoes and she checks me with a portable metal detector like the ones used in airports. Once she’s confident that I’m 100 percent nonmetallic, we enter the scanner room.

I lie on the table and am drawn head first into the white, cylindrical machine. My legs stick out at the end. My head is secured inside a plastic cage-like contraption. It’s an especially tight squeeze because of the plastic prescription goggles I have to wear to see. I can’t wear my regular glasses because of the metal in them. In my right hand, I grasp a joystick, my fingers carefully placed on the buttons. I wonder, purely out of curiosity, if I could climb out of this thing by myself if I had to. In my left hand, I grasp a rubber squeeze bulb like the one on a blood pressure cuff. I can squeeze it at any time to stop the scan if I should feel the need. I decide to proceed and the test goes on.

A special mirror inside projects a computer screen from the next room. The image is of stars in space. I find it ironically appropriate for the situation. I feel like I’m inside a planetarium. Corny Star Trek cliches come to mind. Depending on the day, this machine may become your personal planetarium, movie theater, or video arcade.

This will be my seventh brain scan in two years. But no worries; there’s nothing wrong with me. This is no ordinary scan and I am not at a medical facility. I’m in a lab on the Princeton University campus. Believe it or not, this is my job for today. I am getting an fMRI scan. It stands for functional magnetic resonance imaging. It’s a special type of scan, used only for research purposes. A regular MRI, (without the f), used for medical purposes, takes still pictures of the brain, revealing nothing of the way it works. A functional MRI, on the other hand, shows which areas of your brain you are using to perform mental tasks. It does so by tracking the flow of blood over time in different areas. It is a mainstay of modern neuroscience research.

With a series of loud buzzing sounds, the machine switches from planetarium to arcade. Today’s task: a shape matching game. Point the joystick at each shape as soon as it appears on and press the correct button for each one. Try to score as many points as possible.

I imagine the powerful magnetic field penetrating my body, as I hear the pulsing buzzes and I swear I can almost feel it. The scan takes an hour. In an adjacent room, the inside of my head is on display for all to see. I think to myself, “I’m getting $20 for this?”

Many participants in these studies are college students who do it for course credit. Not me. I am not affiliated with Princeton University in any way, shape, or form. These paid experiments are open to the general public.

Although I have no formal education in science or psychology, I have always been fascinated by science, especially the workings of the human brain. Since high school, whenever I went to the library, I often went for the neuroscience and psychology books first. I also enjoy science documentaries and television shows. So I thought it would be cool to participate in neuroscience experiments. But I always assumed I would have to look to another university, perhaps in New York City, if I wanted to do something like that.

Had it not been for a very unusual post on Craigslist in 2012, I never would have known about the opportunities at Princeton. Checking for freelance gigs in the TV/film/video section, I saw this: “Actress needed to Perform Monologue $1500,” with Princeton listed for the location. I’m no actress, but for that amount of money, it piqued my interest. I clicked the ad and to my surprise, it was for a very involved fMRI study at Princeton University. It was posted by a graduate student from the lab of Professor Uri Hasson, who is known for his research on the phenomenon known as neural coupling. Researchers have found that when people listen to a story their brain activity will match up with that of the person who was telling the story. This was a breakthrough in the understanding of human communication and had received a lot of media attention.

The graduate student was looking to test this theory further. She needed someone to perform a monologue while being scanned so that she could compare that person’s brain activity to her own, when she had performed the same monologue. She needed the person to be scanned multiple times. Unfortunately, I didn’t get to do that particular study because it was canceled, but the ad gave me the idea to Google “paid research at Princeton University.” Princeton does not have a medical program. So I was surprised to find that I could participate in multiple fMRI studies 10 minutes from my house and make money doing it.

Princeton researchers do not normally post on Craigslist. I find out about experiments by checking my account on the Paid Psychology Experiment website otherwise known as Sona, for the name of the company that hosts it. It’s a version of the same website used by many other Ivy League schools for this purpose. Studies are posted there, with lists of available appointment times. Most experiments are designed to take one hour to complete. They are run at various times throughout the week and on weekends, so it is possible to accommodate many work schedules. I usually try to sign up for two studies back to back so I can make at least $24 per trip. Though the labs are all part of Princeton University, they are independent entities and most of their projects are separate.

Most studies don’t pay anything near the $1,500 promised in that Craigslist ad. The pay is $12 per hour for computer tasks and $20 per hour for the more involved experiments like fMRI and EEG. For many studies, you may even receive a few dollars more as a bonus incentive, based on your performance. Depending on the season, I typically make an extra $24 to $40 per month on average. On a few occasions, I’ve made up to $130 in one day for more involved experiments.

The studies take place at a state-of-the art new facility tucked away behind the pedestrian bridge that spans Washington Road. Two stories, plus two basement levels on one side encompass the Princeton Neuroscience Institute. The attached five-story wing is called Peretsman-Scully Hall and is home to the university’s psychology department. Renowned Spanish architect Rafael Moneo’s open and eco-friendly design incorporates numerous glass walls to let in as much natural light as possible. Cheerful doodles and equations reminiscent of “Good Will Hunting” decorate the large windows between offices. This growing academic facility is attracting top scholars from all over the world. I have visited this building many times since it opened in 2014.

As of this writing I have completed seven brain scans, several EEGs, and countless computer-based tasks. Some of the more notable visits include a sleep test where I had to take a 90-minute nap while hooked up to an EEG machine. I have also participated in several experiments where I watched movies. For those, you typically do something like describing what the movie was about or pressing buttons when you see something on screen that you’re supposed to pay attention to.

Some of the more fun ones were the two video arcade-like machines in the lab of professor Jordan Taylor, who investigates the computational processes involved in humans’ motor control skills. One has a special lever on the bottom that senses your movements. It feels like the controls on a piece of construction equipment. You use it move objects on a screen, projected onto a horizontal surface in front of you. The other machine is similar but smaller. You control it with a special pen that has a sensor in it. For each machine, you use either the lever or the pen to throw dots at targets on the screen. They are a lot like the vintage video game, Pong. The purpose is to test their theories on hand-eye coordination.

Those are the more unusual ones. Most paid experiments are a lot less involved. They are simple computer tasks that are sometimes similar to what you see on the Science Channel show, “Brain Games.” Some labs that run them have even been featured on that show before. They typically test things like visual perception, memory, and decision making.

Ones that I have done include repeatedly judging the number of dots on the screen, memorizing pictures, taking surveys, and rating characteristics of faces as they flash on screen. Many of these applications are intended to become fMRI experiments but need to be tested outside the scanner first.

When I was in college 10 years ago, I had a professor who got his PhD in psychology at Princeton in 1954. Scott Parry was still active in the Princeton University community as a carillon player and organist in the University Chapel. He wrote several books on effective communication and workplace training techniques. After selling his consulting firm, Training House Inc., he spent his retirement teaching courses in public speaking and communications at Mercer County Community College, where I was a student.

One of his favorite stories was about the isolation experiments they used to do when he was a graduate student. Researchers put participants in a room with absolutely nothing to do for extended periods of time. To fight the boredom, participants would talk to themselves. They would tell jokes. After a while, they would start to tell the same joke over and over. Ironically, Perry would tell that same story over and over.

Psychology researchers have been known to do bold things. The most famous examples are the Milgram experiment at Yale in 1961 and the Stanford prison experiment in 1971.

The Milgram experiment tested how far people would go when following orders from a perceived authority figure. Participants administered a memory test to an actor who they believed was another participant. They were instructed to give him an electrical shock for each wrong answer and participants were told to increase the strength of the shocks each time he did so. The buttons they pressed to give the shocks didn’t really do anything. The man purposely gave wrong answers. As the strength of the shocks supposedly increased, he would scream and pretend to have chest pains. Experimenters encouraged participants to keep going even when they expressed concern for the man’s wellbeing. They were not always told afterward that the shocks were faked, or that the other man was an actor. Many were deeply disturbed by what they did.

In the Stanford prison experiment college students were divided into groups of “prisoners” and “guards.” To make the experience as authentic as possible, the “prisoners” were even arrested and processed by actual police officers. They were held by the “guards” in a makeshift “jail” on the Stanford University campus. The experiment was intended to last for two weeks, but was called off after six days because participants were taking their roles surprisingly far. The group acting as prisoners rioted and showed signs of extreme emotional distress. The interactions of the “guards” with the “prisoners” became increasingly abusive over the course of the experiment.

Controversial projects like these pushed the boundaries of ethics and precipitated major reforms. Researchers probably couldn’t get away with anything like that today. Researchers can still be vague, however, about what an experiment actually is before you do it. A typical study title may be something like “Reacting to Visual Stimulus.” Then I get there and find out the “stimulus” is actually something like playing cards or looking at pictures of houses. They usually don’t want you to know the true purpose of an experiment ahead of time because that knowledge would bias your performance. So I often go into a test appointment not knowing exactly what to expect.

But there are still lots of rules. This is apparent in the documents I must sign to collect my payments. I am required to sign a consent form telling me what exactly I will be doing during the experiment. Experimenters are required to warn me about any disturbing or upsetting images that may be presented. For fMRI I also sign an additional safety consent form and fill out a basic medical history screening form. All of this information is kept confidential. After the experiment, the researchers are required to debrief me on what it was truly about. I receive a document for that and sign yet another to receive the money.

The address and phone number for Princeton University’s institutional review board (IRB) are everywhere. An IRB is a committee formally designated to approve, monitor, and review biomedical and behavioral research involving humans. The purpose of the IRB is to assure that appropriate steps are taken to protect the rights and welfare of humans participating as subjects in a research study. The IRB must approve all experiments before they are conducted.

Another very important IRB rule is that I can stop the experiment at any time and still collect the money. My first EEG experiment stands out in my mind for this reason.

“Are you sure?” the man says. I forgot that the EEG test required the use of silicone gel in my hair. EEG — electroencephalogram — monitors brainwaves via electrodes placed on your head. “You don’t have to do anything you don’t want to. You can leave right now and I’ll still give you the money,” he says. I think of the Milgram experiment and appreciate his concern. “No, I already showed up, we might as well,” I say. I’d rather not be seen in public with goopy hair, but it’s not that big a deal.

The gel feels cold and slimy as he squirts it onto my head through several small holes in the cap I’m wearing, similar to a bleaching cap. He affixes several electrodes to my face. We enter a room with a thick, scary-looking door that looks like it belongs on a bank vault — or a secret dungeon. Its purpose is to block electrical interference that could drown out the very faint signals from the brain. Radio frequency shielding, they call it. I sit atop a doctor’s office exam table and do the task. I have to memorize words from a list and press a button when they appear on the computer. The researchers administer the test from the next room. They give me instructions through an intercom. I imagine I’m a contestant on some sort of bizarre game show.

This particular test is being run by a post-doctoral associate (post-doc), a recent Ph.D. graduate who intends to eventually teach or run his or her own lab. It’s less common to run across post docs. Most people I meet doing this are graduate students or research assistants.
I finish the test and return to the other room. As I remove the cap, he offers me the use of a large, industrial-looking lab sink to wash the gel out of my hair. A bottle of VO5 shampoo sits on the counter. Cabinets just like the ones from all my high school science classrooms are stacked with neatly folded bath towels.

“What documentaries do you watch?” the post-doc asks. An EEG takes a while to set up and break down, leaving plenty of time to talk. As he disconnects the machine, we chat about things I’ve seen on science shows — how labs are coming up with ways to run fMRI scans on all kinds of animals, even dogs. He explains to me how fMRI scans are done on mice. I tell him how I first got interested in these things watching Scientific American Frontiers with Alan Alda. After his role on MASH, he hosted the series for PBS. He interviewed scientists across the United States and participated in many behavioral experiments. It was one of my favorite television shows when I was in high school.

“I think he’s had his brain scanned for science more times than anybody,” I say.

“Don’t be so sure!” he says in a startlingly matter of fact tone. “Some of us could probably beat his record.” And I thought the seven times I’ve been scanned is a lot! I wanted to find out more.

That man has moved on to a teaching position at another university, so I interview one of his colleagues, Aaron Bornstein. He is a post doc in Princeton’s Computational Memory Lab, under professors Ken Norman and Jonathan Cohen. They study memory and decision making. He doesn’t remember the exact number of times he has been scanned in the past 10 years. “Probably less than 100. Certainly more than 30,” he estimates.

It’s very common for neuroscientists to test experiments for their colleagues when they are in the initial planning stages. “I think it’s just practical for those of us who run fMRI experiments to be scanned regularly, so we get a sense of what it’s like to be inside the scanner,” Bornstein says. For example, he is careful not to change the color and brightness of the screen too rapidly because it sometimes hurts his eyes. He says it’s like when you’re in a dark movie theater and the lights come on. Your eyes have to adjust. “We try to make it very comfortable for people to look at the screens. I [also] try not to keep people in there too long; try to give them lots of breaks. It’s just good to remember what it’s like to be in there.”

I always knew that fMRI is a very safe, innocuous procedure. It doesn’t use dangerous radiation like x-rays or CAT scans do. You don’t have to drink any special liquid or get injected with anything. It works by generating a powerful magnetic field and radio waves. The only serious risk is if you bring metal near the machine. Ferromagnetic metal objects may be pulled forcefully into the machine, causing severe injury if they hit a person. Some nonmagnetic metal objects can also be dangerous because they may get hot and cause burns under certain circumstances. This poses a continuous threat because the magnet cannot be turned off. Some types of nonmagnetic metal implants like braces and permanent retainers can be perfectly safe, but many researchers don’t allow them because they cause small blurry spots on the scan that make certain brain areas harder to see.

That’s why the university takes so many precautions. The researchers have a lengthy screening questionnaire listing every imaginable reason you could have metal in your body. After checking that, the researcher verbally asks if you have certain implants or clothing items. Unlike some facilities, Princeton doesn’t require you to wear a hospital gown, but you are warned in advance to wear clothing with no metal in it. They check you with a portable wand and there are additional metal detectors at the entrances to each of the two scanner rooms.

As long as your body is free of metal, both fMRI and plain medical MRI are thought to be very safe. The only other potential concern is noise from the machine. It’s very loud. That’s why they give you earplugs. Participants are warned that there is a slight possibility of harmless peripheral nerve stimulation, which could cause an uncomfortable tingling sensation. I’ve never experienced that. Claustrophobia can also be an issue. That’s why you’re given a rubber squeeze bulb to hold during the scan. It sets off an alarm to alert researchers if you want to stop the test. People with even the slightest propensity for that problem are urged not to participate.

Universities also take precautions that medical facilities don’t. They want to be sure not to put anyone at unreasonable risk, since there is no medical benefit to justify it. That’s why pregnant women are not allowed to be scanned for research. It’s thought to be safe for the women and fetuses but research facilities err on the side of caution. These policies are mandated by the federal government and the university’s institutional review board.

Surprisingly, there are no limits on the number of times a person can be scanned, though. Surely there must be concern about some possible long-term risk from exposure to the radiofrequency and magnetic fields. I ask Bornstein about this.

“Nope,” Bornstein says confidently. “Before I even started doing fMRI there had been people working and being subjects and having medical MRIs done on them for decades and there haven’t been any problems reported.” Bornstein, who has worked in a number of labs across the country since 2005 and has been at Princeton for the past two-and-a-half years, says he would be more concerned about risk from frequent plane travel than any potential risk from getting scanned so often. And a lot more people fly than get fMRIs. “I think [fMRI] is pretty safe,” he says.

What would Princeton researchers do if someone showed up with a problem like a tumor? “We are not medical doctors,” Bornstein says emphatically. “And the scans that we perform are not medical scans. They’re not likely to detect any kind of real problems.”

The university has a two level certification process for anyone who works with fMRI. For level one, all researchers must take a standard federal human subjects research ethics course and score perfectly on a tough written exam about issues of safety and emergency procedures. To achieve level two, they must train under an existing level two person and pass a two-hour practical exam for which they run through a scan session and discuss proper responses to every possible emergency. Only level two people are allowed to actually operate the machine.

The university has protocols in place in case there is a suspicious finding on a participant’s scan. But these experiments are no replacement for medical tests. If they do happen to find something, they will tell the participant to get checked by a licensed medical doctor.

Neuroscience is a diverse field that crosses many academic disciplines. Neuroscientists may have backgrounds in psychology, computer science, molecular biology, physics, or math, just to name a few. Originally from New York, Bornstein has a bachelor’s degree in mathematics from MIT and a PhD in psychology from NYU. “I got into the field because I thought it was an interesting question: how does the brain work?”

He has previously worked in computer security and knows how to write software. He writes these game-like computer based experiments that he uses in his research. This is common at Princeton. “It’s not necessarily the same as writing the production software that you would see shipped by a commercial company, but you do have to write software,” says Bornstein. “I think everyone here knows how to program at least a little bit.”

He is particularly interested in studying how people make decisions about money. He designs computer-based behavioral tasks to test his theories. The few I have participated in typically involved learning associations between pictures of places and objects. They tended to be the type of task where you could earn extra money based on your performance.

A common theme on science shows is self-discovery. Countless documentaries show people finding out all kinds of revelations about themselves: Answers to lifelong questions. Why they’re good at music. Why they have struggled with a particular learning disability. Don’t expect to have that experience doing paid experiments at Princeton. You will be disappointed. When you see something like that, it’s likely the end result of years of research.

It takes a long time to get to that point. It can take months just to analyze the results from a single experiment. Researchers aren’t able to tell you anything about your brain activity right after a scan. Says Bornstein: “There’s very little you can tell about a person from the kinds of studies we do. It’s not clear that the field knows enough about individual variation yet.” The particular field to which he refers is computational neuroscience. Much of Bornstein’s work is about finding better ways to collect and analyze data. “We know quite a bit about what brains do in general, but the range of differences among people is still a matter of significant research,” he says.

One reason for that, Bornstein says, is “because the data is very noisy and so what you need is an average of many, many people. We do about 32 people per study now. And that will give you reasonable, statistical effects.” Some examples of “noise” would be fluctuations in the magnetic field, or the person’s mind wandering at a particular moment while they are being scanned. Researchers need to be sure that brain activity they observe is actually from the experiment and not one of those other factors. They need to collect a lot of data from a lot of people before they can know for sure. “The hope is that if a single person does hundreds of repetitions of the experiment, hundreds of trials within the experiment, and many, many people do it over and over again, that all that noise would just average out,” says Bornstein. That’s why many behavioral experiments will have you repeat the same action for the duration of the study. Think rounds on a game show, or levels in a video game.

It’s also why people who are left-handed are excluded from some experiments. Researchers want to be sure that everyone is doing the task in a consistent way. For example, all subjects may be expected to use their right hand to press buttons in a computer game, and reaction time may be slower in people for whom that is not their dominant hand.

Every research technique has its benefits and drawbacks. One drawback of fMRI is that it’s only correlational, not causational. In other words it observes what the brain does, but doesn’t show cause and effect. Just because more blood flows to a certain area when you do a task, it doesn’t necessarily mean that it’s because that part of the brain is needed for the task. This isn’t an issue for Bornstein because he’s only interested in observing.

I talk to another researcher, Taylor Webb, a fourth-year graduate student who wants to take things to the next level. To do that he uses a more intrusive research technique — a tool that actually does something to the brain. This is the most surprising type of human experiment being done at Princeton and the only one I haven’t personally experienced. It’s a machine that sends pulses of magnetic energy into the surface of the brain in order to directly affect its function. This technique is called transcranial magnetic stimulation, or TMS.

If you Google “TMS,” you will find videos of it being used for some pretty amazing things. Depending on where the magnet is placed on a person’s head, it can have a variety of effects. If it is placed over the brain’s sensory motor strip, it causes a person’s fingers to move. If it is placed over a person’s speech center while they talk, it momentarily disrupts their speech. Scientists are using it to treat autism symptoms with surprising success and figuring out how to enhance brain function of healthy people in all kinds of ways. It is used therapeutically to treat depression and is being studied for use in other mental illnesses, as well.

This is absolutely not to be confused with ECT, or electroconvulsive therapy, commonly known as electro-shock therapy. Though both can be used to treat depression, ECT and TMS are very different. ECT is a medical procedure, done only in a hospital setting with anesthesia. ECT administers an electrical shock to a large area of the brain in order to produce a seizure. The seizure is thought to help depression symptoms. Side effects include memory loss and confusion.

TMS only briefly affects very small, pinpointed brain areas. It doesn’t have significant side effects and the last thing researchers ever want to do is to cause a seizure. TMS is performed by placing a figure-eight-shaped magnet, called a coil, over a person’s head, above the brain area they want to stimulate. The coil is attached to a machine.

It doesn’t produce a direct electrical current that gives you a shock in the traditional sense. It works instead through electromagnetic induction. The TMS coil induces a strong but spatially confined magnetic field around itself. When a magnetic field changes in strength very rapidly (turning on and off for a fraction of a second), the field can induce a corresponding electrical signal in a conductor under the coil. In this case, neurons in the brain act as the conductor. Says Webb: “It can only effect superficial areas of the brain (areas that are on the surface). It affects a one to two-centimeter-wide area of the cortex, no deeper than that. That sort of scrambles the signals being made in that brain region, so you can very, very slightly impair function in that brain region, very temporarily, and test the effects that it has.”

So what amazing thing is this machine being used for at Princeton? Studying consciousness. Webb works in the lab of professor Michael Graziano, who is well known in this field of study. Graziano has written several books, including the popular “God, Soul, Mind, Brain” and “Consciousness and the Social Brain.” He has also written several fiction and children’s books. He uses a orangutan puppet named Kevin to demonstrate his theories in lectures and public demonstrations. Graziano is also known for his discoveries about how the human sensory motor strip in the brain works. He used TMS to prove that the body map within the brain is a lot more intricate and detailed than previously believed. Graziano and his colleagues have a specific theory about the relationship between attention and consciousness.

The opportunity to use TMS to test this theory is what attracted Webb to Princeton after receiving his undergraduate degree in neuroscience from the University of Southern California. Specifically, the researchers are interested in unconscious effects on attention. “There are subliminal stimuli that participants aren’t conscious of but we can show [that it] impact[s] their attention in subtle ways,” Webb says. This means that people can still technically see something and respond to it, even if they are not consciously aware that they see it.

“We think that a region in the parietal lobe plays an important role in that,” Webb says. “We see that region becomes active when people are conscious of stimuli but not when people are unconscious of them, even when those stimuli are drawing attention. So it doesn’t have to do with attention, it’s more about consciousness.”

The specific brain area he studies is called the temporoparietal junction (TPJ). You actually have two temporoparietal junctions. They are located slightly above and behind the ear on each side of your head. This is an important brain area that is of interest to many scientists. It has been found to be involved in information processing and the perception of oneself and others. Webb is studying the role it plays in consciousness and controlling attention. He explores this by testing how people respond to visual cues that they are not consciously aware of.

I have never had TMS myself, but I have participated in several versions of Webb’s studies that will eventually include it. His experiments most remind me of something I’d expect to do at an eye doctor’s office. You sit in a special adjustable chair, usually with your head in a chin rest, and press buttons when you see a particular object that you’re supposed to pay attention to. Objects may be letters, numbers, or shapes, that flash on screen very quickly.

The general goal of these experiments is to test whether you can still see an object and respond to it without being consciously aware that you see it. He wants to see if and how often you will press buttons in response to objects you saw on the screen, even if you’re not consciously aware of them because they flashed too quickly, and if these stimuli will affect which parts of the screen you pay attention to. “Basically our main question is, if we apply TMS to this region of the parietal cortex, the TPJ, will it make people less likely to become aware of that stimulus — to notice that subtle difference? And as a separate question, will it make it so that the stimulus doesn’t draw attention? Our hypothesis is that those two things are independent. It might still draw attention even though people are less likely to become conscious of it.”

The effects you can expect from participating in Webb’s experiments are likely to be far less dramatic than what they show in science documentaries. There are actually two types of TMS. The more popular type is called repetitive TMS, or rTMS. This is the kind of machine that’s used for therapeutic purposes and produces the more dramatic, noticeable effects. It delivers a series of repeated magnetic pulses. It is intended to make lasting and permanent changes to brain function, which may last for hours or even weeks after the treatment.

The kind used at Princeton is called single pulse TMS. It only delivers one pulse at a time. It works the same way as rTMS but is much weaker and doesn’t have a lasting effect on the brain. “The only thing that is subjectively noticeable from single pulse TMS at this strength is if I put it over the part of your motor cortex that controls your fingers, I can elicit twitches in specific fingers,” Webb says. The effect is very small and wears off in seconds. Says Webb: “We can time it so that in a trial, a particular few hundred millisecond chunk of time has an effect, but it’s not something that’s going to last even onto the next trial, much less later in the day.” He says that using a stronger machine would actually defeat the purpose of his research because he wants to see how performance on the task is affected from moment to moment.

In order to pinpoint the correct brain area, each participant must first undergo an MRI. Webb doesn’t stimulate the same area in each participant. He uses TMS on the right or left side and in some subjects stimulates a slightly different location to act as a control. That would be a brain area slightly outside of the TPJ that he doesn’t think will affect the experiment. That’s how he accounts for any placebo effect.

The temporoparietal junctions are located in the same general area in everyone, but the exact location varies from person to person. He says it can actually vary by up to a few centimeters, which is a lot. So he needs the MRI data to pinpoint the correct location for each participant so that he can properly calibrate the TMS machine.

During the TMS session the participant wears a head band that has three protruding reflective points. The TMS coil has three corresponding reflective points on it. A camera in the corner of the ceiling tracks the relative positions of the coil and the person’s head. A special computer program calculates where the center of the coil is relative to the part of the brain they want to stimulate.

The biggest safety concern with TMS is the small risk of seizures. “If someone has an underlying tendency toward epilepsy or if it’s known that they have epilepsy then we definitely wouldn’t do TMS on that person,” says Webb. “It’s the sort of thing that if you’re already very likely to have a seizure, this could provide the just the little bit of extra oomph that it needs to go over the edge into causing a seizure. From single pulse TMS at strengths much higher than [our machines] go, there’s one recorded instance of having caused a seizure in someone who is already known to have epilepsy. At these strengths in normal people who don’t have already known cases of epilepsy, there are no actual instances of causing a seizure.”

To be able to use this machine, Webb had extensive training and was certified by the university. So far he has only run one TMS experiment. He has used the machine about 40 to 50 times on about 30 people.

How do people react to the experiment? Do they get nervous? “They usually seem fine about the TMS itself. I would say that the tasks I have participants do are probably a little bit on the boring side,” he says. Webb says the participants are not usually any more nervous about the procedure than they are about getting an fMRI scan for the first time. “The first thing that I always do is I apply a TMS pulse to the participant’s wrist, just so they know what it feels like at the lowest strength possible and then slowly raise it so they understand what they’re getting into, and just make it totally clear that if you want to opt out of this at any point, that’s totally fine,” he says. “I’ve never had that happen. I would say basically, in terms of what it feels like, it feels like just sort of a light flick. At most I would say it’s kind of annoying — but not painful.”

I ask Webb what his friends and family think of his work. “I think people are usually a little bit surprised that you can noninvasively stimulate someone’s brain. But I think that once I describe how weak the effect is, I think it’s maybe less surprising. The effect is at a threshold level so it’s not like mind control or something like that. It’s a very subtle effect. It’s easy for people to get almost a sci-fi impression of it, but I think once you describe it more concretely, it makes more sense.”
At the time of our interview Webb is recruiting participants for another TMS experiment he will be running shortly. The pay is $20 per hour. Participants can potentially make $80 to $400 for the whole experiment, depending on the number of times they participate.
Another Monday is upon me. I check my account on the paid experiment website again. Two new studies are posted that I haven’t done. Just my luck, they both have back-to-back time slots for the coming Saturday, perfect! I essentially press buttons on a computer for an hour — and get to meet fascinating people who are on the cutting edge of science. A most unusual way to fund my shopping excursions in downtown Princeton, but for $12 an hour I think it’s a good deal.