Delusions: Making Sense of Mistaken Senses


For a common affliction that strikes people of every culture and walk of life, schizophrenia has remained something of an enigma. Scientists talk about dopamine and glutamate, nicotinic receptors and hippocampal atrophy, but they’ve made little progress in explaining psychosis as it unfolds on the level of thoughts, beliefs, and experiences. Approximately one percent of the world’s population suffers from schizophrenia. Add to that the comparable numbers of people who suffer from affective psychoses (certain types of bipolar disorder and depression) or psychosis from neurodegenerative disorders like Alzheimer’s disease. All told, upwards of 3% of the population have known psychosis first-hand. These individuals have experienced how it transformed their sensations, emotions, and beliefs. Why hasn’t science made more progress explaining this level of the illness? What have those slouches at the National Institute of Mental Health been up to?

There are several reasons why psychosis has proved a tough nut to crack. First and foremost, neuroscience is still struggling to understand the biology of complex phenomena like thoughts and memories in the healthy brain. Add to that the incredible diversity of psychosis: how one psychotic patient might be silent and unresponsive while another is excitable and talking up a storm. Finally, a host of confounding factors plague most studies of psychosis. Let’s say a scientist discovers that a particular brain area tends to be smaller in patients with schizophrenia than healthy controls. The difference might have played a role in causing the illness in these patients, it might be a direct result of the illness, or it might be the result of anti-psychotic medications, chronic stress, substance abuse, poor nutrition, or other factors that disproportionately affect patients.

So what’s a well-meaning neuroscientist to do? One intriguing approach is to study psychosis in healthy people. They don’t have the litany of confounding experiences and exposures that make patients such problematic subjects. Yet at first glance, the approach seems to have a fatal flaw. How can you study psychosis in people who don’t have it? It sounds as crazy as studying malaria in someone who’s never had the bug.

In fact, this approach is possible because schizophrenia is a very different illness from malaria or HIV. Unlike communicable diseases, it is a developmental illness triggered by both genetic and environmental factors. These factors affect us all to varying degrees and cause all of us – clinically psychotic or not – to land somewhere on a spectrum of psychotic traits. Just as people who don’t suffer from anxiety disorders can still differ in their tendency to be anxious, nonpsychotic individuals can differ in their tendency to develop delusions or have perceptual disturbances. One review estimates that 1 to 3% of nonpsychotic people harbor major delusional beliefs, while another 5 to 6% have less severe delusions. An additional 10 to 15% of the general population may experience milder delusional thoughts on a regular basis.

Delusions are a common symptom of schizophrenia and were once thought to reflect the poor reasoning abilities of a broken brain. More recently, a growing number of physicians and scientists have opted for a different explanation. According to this model, patients first experience the surprising and mysterious perceptual disturbances that result from their illness. These could be full-blown hallucinations or they could be subtler abnormalities, like the inability to ignore a persistent noise. Patients then adopt delusions in a natural (if misguided) attempt to explain their odd experiences.

An intriguing study from the early 1960s illustrates how rapidly delusions can develop in healthy subjects when expectations and perceptions inexplicably conflict. The study, run on twenty college students at the University of Copenhagen, involved a version of the trick now known as the rubber hand illusion. Each subject was instructed to trace a straight line while his or her hand was inside a box with a secret mirror. For several trials, the subject watched his or her own hand trace the line correctly. Then the experimenters surreptitiously changed the mirror position so that the subject was now watching someone else’s hand trace the straight line – until the sham hand unexpectedly veered off to the right! All of the subjects experienced the visible (sham) hand as their own and felt that an involuntary movement had sent it off course. After several trials with this misbehaving hand, the subjects offered explanations for the deviation. Some chalked it up to their own fatigue or inattention while others came up with wilder, tech-based explanations:

 . . . five subjects described that they felt something strange and queer outside themselves, which pressed their hand to the right or resisted their free mobility. They suggested that ‘magnets’, ‘unidentified forces’, ‘invisible traces under the paper’, or the like, could be the cause.

In other words, delusions may be a normal reaction to the unexpected and inexplicable. Under strange enough circumstances, anyone might develop them – but some of us are more likely to than others.

My next post will describe a clever experiment that planted a delusion-like belief in the heads of healthy subjects and used trickery and fMRI to see how it influenced some more than others. So stay tuned. In the meantime, you may want to ask yourself which members of your family and friends are prone to delusional thinking. Or ask yourself honestly: could it be you?


Photo credit: MiniTar on Flickr, available through Creative Commons

Modernity, Madness, and the History of Neuroscience


I recently read a wonderful piece in Aeon Magazine about how technology shapes psychotic delusions. As the author, Mike Jay, explains:

Persecutory delusions, for example, can be found throughout history and across cultures; but within this category a desert nomad is more likely to believe that he is being buried alive in sand by a djinn, and an urban American that he has been implanted with a microchip and is being monitored by the CIA.

While delusional people of the past may have fretted over spirits, witches, demons and ghouls, today they often worry about wireless signals controlling their minds or hidden cameras recording their lives for a reality TV show. Indeed, reality TV is ubiquitous in our culture and experiments in remote mind-control (albeit on a limited scale) have been popping up recently in the news. As psychiatrist Joel Gold of NYU and philosopher Ian Gold of McGill University wrote in 2012: “For an illness that is often characterized as a break with reality, psychosis keeps remarkably up to date.”

Whatever the time or the place, new technologies are pervasive and salient. They are on the tips of our tongues and, eventually, at the tips of our fingers. Psychotic or not, we are all captivated by technological advances. They provide us with new analogies and new ways of explaining the all-but-unexplainable. And where else do we attempt to explain the mysteries of the world, if not through science?

As I read Jay’s piece on psychosis, it struck me that science has historically had the same habit of co-opting modern technologies for explanatory purposes. In the case of neuroscience, scientists and physicians across cultures and ages have invoked the  innovations of their day to explain the mind’s mysteries. For instance, the science of antiquity was rooted in the physical properties of matter and the mechanical interactions between them. Around 7th century BC, empires began constructing great aqueducts to bring water to their growing cities. The great engineering challenge of the day was to control and guide the flow of water across great distances. It was in this scientific milieu that the ancient Greeks devised a model for the workings of the mind. They believed that a person’s thoughts, feelings, intellect and soul were physical stuff: specifically, an invisible, weightless fluid called psychic pneuma. Around 200 AD, a physician and scientist of the Roman Empire (known for its masterful aqueducts) would revise and clarify the theory. The physician, Galen, believed that pneuma fills the brain cavities called ventricles and circulates through white matter pathways in the brain and nerves in the body just as water flows through a tube. As psychic pneuma traveled throughout the body, it carried sensation and movement to the extremities. Although the idea may sound farfetched to us today, this model of the brain persisted for more than a millennium and influenced Renaissance thinkers including Descartes.

By the 18th century, however, the science world was a-buzz with two strange new forces: electricity and magnetism. At the same time, physicians and anatomists began to think of the brain itself as the stuff that gives rise to thought and feeling, rather than a maze of vats and tunnels that move fluid around. In the 179os, Luigi Galvani’s experiments zapping frog legs showed that nerves communicate with muscles using electricity. So in the 19th century, just as inventors were harnessing electricity to run motors and light up the darkness, scientists reconceived the brain as an organ of electricity. It was a wise innovation and one supported by experiments, but also driven by the technical advances of the day.

Science was revolutionized once again with the advent of modern computers in the 1940s and ‘50s. In the 1950s, the new technology sparked a surge of research and theories that used the computer as an analogy for the brain. Psychologists began to treat mental events like computer processes, which can be broken up and analyzed as a set of discrete steps. They equated brain areas to processors and neural activity in these areas to the computations carried out by computers. Just as computers rule our modern technological world, this way of thinking about the brain still profoundly influences how neuroscience and psychology research is carried out and interpreted. Today, some labs cut out the middleman (the brain) entirely. Results from computer models of the brain are regularly published in neuroscience journals, sometimes without any data from an actual physical brain.

I’m sure there are other examples from the history of neuroscience in general and certainly from the history of science as a whole. Please comment and share any other ways that technology has shaped the models, themes, and analogies of science!

Additional sources:

Crivellato E & Ribatti D (2007) Soul, mind, brain: Greek philosophy and the birth of neuroscience. Brain Research Bulletin 71:327-336.

Karenberg A (2009) Cerebral Localization in the Eighteenth Century – An Overview. Journal of the History of the Neurosciences, 18:248-253.


Photo Credit: dominiqueb on Flickr, available through Creative Commons

Plastic and the Developing Brain


When I was pregnant with my daughter, I had enough on my mind. I didn’t have much time to think much about plastic. I knew vaguely that plastics can release estrogen-mimicking substances like bisphenol A (BPA) into our food and I’d heard that they might cause genital defects in male fetuses. But once my husband and I had the 20-week ultrasound and knew we were having a girl, I thought I could stop searching for products in cardboard or glass. It was just too hard. Everything is packaged in plastic these days.

Apparently I jumped the gun.

Scientific papers warning about the hazards of prenatal exposure to BPA have been coming out in a steady stream, with a string of particularly damning ones appearing over the last 18 months in the Proceedings of the National Academy of Sciences. Last month one in particular caught my eye: a study of how prenatal BPA exposure changes the brain. The results were enough to make this neuroscientist pause.

While we tend to think of estrogens as the sex hormones that manage ovulation and pregnancy, these molecules also have powerful and direct effects on the brain. Many types of neurons have estrogen receptors on their outer surface. While there are several kinds of estrogen receptors in the brain, all bind to estrogens (and other molecules that resemble estrogens) and all trigger changes within their neurons as a result. These small changes can potentially add up to alter how entire neural circuits function. In fact, estrogens influence a wide range of skills and behaviors – from cognitive function to mood regulation and even fine motor control. While we don’t yet know why estrogens have such a broad and powerful influence on the brain, it does appear that we should think twice before mucking around with estrogen levels, particularly in the developing brain.

BPA and other compounds found in plastics resemble estrogens. The similarity is close enough to fool estrogen receptors, which bind to these foreign molecules and interpret them as additional estrogen. Although BPA has been used commercially as a dental sealant and liner for food containers (among many other uses) since the 1960s, the health consequences of this case of mistaken identity are just beginning to be understood.

In the PNAS paper published last month, a group of scientists headed by Dr. Frances Champagne at Columbia report the effect of prenatal BPA exposure on mice. They fed pregnant laboratory mice one of three daily doses of BPA (2, 20, or 200 μg/kg) or a control product without BPA. These are not high doses of BPA. Based on the amount of BPA found in humans, scientists estimate that we are exposed to about 400 μg/kg per day. The U.S. Food and Drug Administration reached their own estimate by testing the amount of BPA in various foods and then approximating how much of these people consume daily. Their calculations put the figure at around 0.19 μg/kg daily for adults. This discrepancy (400 versus 0.19) is one of many points of contention between the FDA, the packaging industry, and the scientific community on the subject of BPA.

Champagne and her colleagues fed their mice BPA on each of the twenty days of mouse gestation. (That’s right, ladies: mouse pregnancies last less than three weeks.) After each mouse pup was born, the scientists either studied its behavior or sacrificed it and examined its brain.

What did they find? Prenatal BPA exposure had a noticeable impact on mouse brains, even at the lowest dose. They found BPA-induced changes in the number of new estrogen receptors being made in all three brain areas they examined: the prefrontal cortex, hypothalamus, and hippocampus. These effects were complex and differed depending on the gender of the animal, the brain area, the BPA dose, and the type of estrogen receptor. Still, in several cases the researchers found a surprising pattern. Without BPA-exposure, female mice typically made more new estrogen receptors than their male counterparts. The same was true for mice given the highest BPA dose. But among pups exposed to the two lowest BPA doses, male mice made more estrogen receptors than females! This sex-difference reversal stemmed from changes in both genders; male mice made more estrogen receptors than normal at these doses while female mice made fewer than their norm.

Champagne and colleagues also observed and recorded several behaviors of the mice in different circumstances. For most behaviors, males and females were naturally different from one another.  Just as human boys tend to chase each other more than girls do, male mouse pups chased more than females. Unexposed male mice sniffed a new mouse more than unexposed females did. They showed more anxiety-like behavior in an open space and were less active in their home cages. Prenatal BPA treatment reversed these natural sex differences. Exposed female mice did more sniffing, acted more anxious, and ran around less than their exposed male counterparts. And at the highest prenatal BPA dose, the male mice chased each other as rarely as the females did. In one case, BPA treatment affected the two genders similarly; both sexes were less aggressive than normal at the two lower doses and more aggressive than normal at the highest dose.

Overall, the results of the study are complex and it might be easy to ignore them because they don’t seem to tell a straightforward tale. Yet their findings can be summed up in a single sentence: BPA exposure in utero has diverse effects on the mouse brain and later behavior. Not only does the BPA ingested by the mom manage to affect the growing fetus, but those effects persist beyond the womb and past the end of the exposure to BPA.

Some will dismiss these results because they come from mice. After all, how much do we really resemble mice? Yet studies in monkeys have also found that BPA affects fetal development. And while mice and monkeys excrete BPA differently, they clear it at a similar rate — to each other and to human women. Results from correlational studies in humans also suggest that BPA exposure during development affects mood, anxiety and aggressiveness to varying degrees (depending on the child’s gender).

Still, there’s a lot we don’t know about the relevance of this study for humans. At the end of the day, mice aren’t humans and no one has agreed on how much BPA pregnant women ingest. Moreover, Champagne and colleagues examined only a small subset of the neural markers and behaviors that BPA might affect in mice. Perhaps the changes they describe are the worst of BPA’s effects, or perhaps they are only the tip of the iceberg. We don’t yet know.

What’s the upshot of all this? You may want to err on the side of caution, particularly if you’re pregnant. Avoid plastics when possible. Be aware of other sources of BPA like canned foods (which have plastic liners) and thermal receipts. Do what you can do and then try not to let it stress you out. If you’re pregnant, you already have enough on your mind.

As for my daughter, she seems to be fine despite her plasticized third trimester. While she doesn’t do much sniffing, she does occasionally slap my husband or me in the face. It could be the BPA making her aggressive. I choose to blame it on her sassy genes instead.


Photo credit: .imelda on Flickr

Kundakovic M, Gudsnuk K, Franks B, Madrid J, Miller RL, Perera FP, & Champagne FA (2013). Sex-specific epigenetic disruption and behavioral changes following low-dose in utero bisphenol A exposure. Proceedings of the National Academy of Sciences of the United States of America, 110 (24), 9956-61 PMID: 23716699

My Body or Yours?


Today we’re talking bodies. Not how they look in skinny jeans or whether they can win a Tour de France without steroids. We’re talking about how it feels to have a body of your own, one that is (or seems to be) conveniently connected to your head and neck.

I’ve written about body ownership before in the context of pregnancy. Although I focused on how I dreamt of my body during sleep, I also mentioned that my ballooning physical dimensions affected my coordination. I’d bump into countertops or doorways with my big belly and sometimes struggled to locate my center of gravity. Yet as strange as my new body was, it always felt like it belonged to me. This was an enormous blessing, of course, but it’s somewhat surprising  as well. After all, before my pregnancy I’d lived with the same body since puberty. After more than a decade and a half of experience with that body, I suddenly had to adjust to my new body in a matter of months. Or rather days, because that new body kept growing larger still. Although my belly would feel surreal at times, overall I had remarkably little trouble adjusting to my metamorphosis. The body was still mine in all its lumpy glory.

I was reminded of this experience recently when I came across a scientific paper about body swapping. I know it sounds as if the only science in something called body swapping must come from the term science fiction. Actually, body swapping is a remarkable perceptual illusion that requires nothing more than a second person, a set of head mounted cameras and a set of head mounted displays. Someone facing you wears the cameras mounted on a helmet and you wear the visual displays (which are presented to your two eyes like goggles as part of a virtual reality-style headset). The camera footage, filmed from the visual perspective of the second person, is fed directly into your visual display. Thus, you see your own body from the second person’s perspective.

But we haven’t made it to Freaky Friday just yet. The illusion requires something more. You and the other person take each other’s hands and begin squeezing them simultaneously. Nothing fancy. But in the words of the write up by Valeria Petkova and Henrik Ehrsson, this simple setup alone “. . . evoked a vivid illusion that the experimenter’s arm was the participant’s own arm and that the participants could sense their entire body just behind this arm. Most remarkably, the participants’ sensations of the tactile and muscular stimulation elicited by the squeezing of the hands seemed to originate from the experimenter’s hand, and not from their own clearly visible hand.”

So after a lifetime in your own body, it only takes a video feed and a few hand squeezes for you to make yourself at home in someone else’s arms and legs. If this setup sounds familiar, it is a more impressive incarnation of the classic rubber hand illusion. And a new and remarkable twist on the illusion just appeared in the news: scientists in the same lab have made people feel as if they have an invisible hand. (For a great discussion of this new illusion, read this.)

In science, we tend to think about human perception in general and illusions in particular in terms of adaptations and optimizations. Lots of visual illusions are based on the statistical probability of objects and events in our environment. Our brains learn to predict and extrapolate information about our settings because they jump to the likeliest conclusions. In this way illusions, while technically errors, often reveal clever shortcuts our brain takes to help us understand or parse our surroundings faster, better, or at less of an energy cost.

But what about the body swap? Since we never actually swap bodies, why should we mentally be able to do it? What’s the advantage? Well, the advantage seems to come down to the very fact that we never actually swap bodies. In our ever-changing world, a rare given is that you will have the same body tomorrow that you had today and yesterday. So why should your brain waste precious time or energy soliciting proof from every finger and toe, curve and joint, flex and bend? Take a smidge of visual evidence (in this case, the video display) and a dab of tactile confirmation (hand squeezing) and you have a recipe for body ownership. How often in the natural world would this recipe ever lead you astray?

So in essence you only think that you feel that you own your body. In truth, your brain is creating that sensation on the fly all the time. You could think of it as a philosophical conundrum or cause for an existential crisis. I prefer to think of it as good news for pregnant ladies everywhere.


Photo credit: Elizabeth Tan

Petkova VI, & Ehrsson HH (2008). If I Were You: Perceptual Illusion of Body Swapping PLOS One DOI: 10.1371/journal.pone.0003832

The End of History

Intersection 12-12-12 Day 347 G+ 365 Project 12 December 2012I just read a wonderful little article about how we think about ourselves. The paper, which came out in January, opens with a tantalizing paragraph that I simply have to share:

“At every stage of life, people make decisions that profoundly influence the lives of the people they will become—and when they finally become those people, they aren’t always thrilled about it. Young adults pay to remove the tattoos that teenagers paid to get, middle-aged adults rush to divorce the people whom young adults rushed to marry, and older adults visit health spas to lose what middle-aged adults visited restaurants to gain. Why do people so often make decisions that their future selves regret?”

To answer this question, the study’s authors recruited nearly 20,000 participants from the website of “a popular television show.” (I personally think they should have told us which one. I’d imagine there are differences between the people who flock to the websites for Oprah, The Nightly News, or, say, Jersey Shore.)

The study subjects ranged in age from 18 to 68 years of age. For the experiment, they had to fill out an online questionnaire about their current personality, core values, or personal preferences (such as favorite food). Half of the subjects—those in the reporter group—were then asked to report how they would have filled out the questionnaire ten years prior, while the other half—those in the predictor group—were asked to predict how they will fill it out ten years hence. For each subject, the authors computed the difference between the subject’s responses for his current self and those for his reported past self or predicted future self. And here’s the clever part: they could compare participants across ages. For example, they could compare how an 18-year-old’s prediction of his 28-year-old future self differed from a 28-year-old’s report of his 18-year-old self. It sounds crazy, but they did some great follow up studies to make sure the comparison was valid.

The results show a remarkable pattern. People believe that they have changed considerably in the past, even while they expect to change little in the future. And while they tend to be pretty accurate in their assessment of how much they’ve changed in years passed, they are grossly underestimating how much they will change in the coming years. The authors call this effect The End of History Illusion. And it’s not just found in shortsighted teenagers or twenty-somethings. While the study showed that older people do change less than younger people, they still underestimate how much they will continue to change in the decade to come.

The End of History Illusion is interesting in its own right. Why are we so illogical when reasoning about ourselves – and particularly, our own minds? We all understand that we will change physically as we age, both in how well our bodies function and how they look to others. Yet we deny the continued evolution (or devolution) of our traits, values, and preferences. We live each day as though we have finally achieved our ultimate selves. It is, in some ways, a depressing outlook. As much as we may like ourselves now, wouldn’t it be more heartening to believe that we will keep growing and improving as human beings?

The End of History Illusion also comes with a cost. We are constantly making flawed decisions for our future selves. As the paper’s opening paragraph illustrated, we take actions today under the assumption that our future desires and needs won’t change. In a follow up study, the authors even demonstrate this effect by showing that people would be willing to pay an average of $129 now to see a concert by their favorite band in ten years, while they would only be willing to pay an average of $80 now to see a concert by their favorite band from ten years back. Here, the illusion will only cost us money. In real life, it could cost us our health, our families, our future well-being.

This study reminded me of a book I read a while back called Stumbling on Happiness (written, it turns out, by the second author on this paper). The book’s central thesis is that we are bad at predicting what will make us happy and the whole thing is written in the delightful style of this paper’s opening paragraph. For those of you with the time, it’s worth a read. For those of you without time, I can only hope you’ll have more time in the future. With any luck we’ll all have more – more insight, more compassion, more happiness—in the decade to come.


Photo credit: Darla Hueske

Quoidbach J, Gilbert DT, & Wilson TD (2013). TheEnd of History Illusion Science DOI: 10.1126/science.1229294

Sandy, Science, and a New Campaign

As Tuesday’s election approaches and news coverage of super storm Sandy recedes, I’m struck by the absurdity of our current situation. While cities on the East Coast are still pumping water out of tunnels and salvaging belongings from ruined homes, we get back to talking about the economy. That and reproductive rights.

Yet we are surrounded by evidence of climate change, even beyond our recent run-ins with Sandy and Irene. We have seen increases in the frequency and severity of storms, droughts, and wildfires. Already, drought has affected food prices here in the U.S. and caused widespread famine in Africa. Massive ice shelves in Antarctica are melting and crumbling into the sea, demonstrably raising sea levels worldwide. And this past year brought us record-breaking temperatures, one after another, as we watched a freakishly warm winter give way to a sweltering summer.

Despite the mountain of scientific evidence that climate change is real and ample demonstrations of the devastation it can wreak, the topic has not been an issue in this year’s presidential election. It wasn’t discussed in any of the three presidential debates. This is not an oversight on the part of the candidates and the moderators. Americans are simply not worried about climate change. In a Gallup poll from September, only 2% of respondents ranked environmental issues as the most important problem facing our country today. Most ranked unemployment and our lagging economy as the nation’s greatest woe.

While people are certainly suffering in today’s economy, the dismissal of climate change is terribly shortsighted. Climate change is an economic threat. It has already raised (and will probably continue to raise) the cost of food. We have also faced steep costs as a result of extreme weather. New York State’s economy alone lost as much as 18 billion dollars due to Sandy and fortifying New York from future flooding could cost upwards of 20 billion dollars. Those figures don’t include the damage in other states and they don’t include the expense to homeowners who are rebuilding or who will try to insure their homes in the wake of this storm. And of course it can’t include the personal devastation and loss of life.

So why aren’t we talking more about climate change? And why aren’t we doing more, both in our own lives and in our voting choices, to try to stem the tide?

It seems to me that we are witnessing a human psychology experiment on the grandest scale. How can we ignore (and in fact perpetuate) an impending disaster of such magnitude? In fact, humans have quite a bit of practice at ignoring future doom. After all, we live out our lives with the certainty that we will die and we function in large part by not thinking about it. Death? What death? Climate change? What change?

I wrote before about how our disappearing glaciers may be suffering from a PR problem. They need a spokesman or a mascot – something that might tug at our heartstrings and make people care. Now I think we need a similar approach for climate change itself. The climatologists have done their job and demonstrated that climate change is real. But our first and greatest obstacle in fixing it may lie within ourselves or, more specifically, our skulls.

I think it’s time to call in the psychologists, the marketing specialists and the public relations gurus. Through years of research, we already know the many ways that human beings are illogical and we know how to persuade and manipulate them. Beer has bikini-clad women. Cigarettes have cowboys. Viagra and Cialis have politicians and quarterbacks. Why can’t we do the same for our planet? It’s time we held focus groups and raised ad dollars. It’s time for a climate campaign.

Popular opinion has always driven political will. We need to use every resource we have to raise awareness and change minds. So let’s bring in the psychologists. Let’s bring in the bikini-clad women if need be. (After all, it’s going to be hot!) But before we can influence others, we have to begin by changing ourselves. By changing our lifestyles. By changing our priorities. By changing our minds and then voting our minds. And there’s no better time to start than this Tuesday.

I’ll see you at the ballot box!

Tooling Around

tools1There was a time when my daughter used her hands exclusively to shovel things into her mouth. Not so anymore. For the last few months, she has been hard at work banging objects together. This simple action is setting the stage for some pretty cool neural development. She is learning to use tools.

Of course it doesn’t look too impressive right now. She might bang a ball with a block and then switch and strike the block with the ball. In one recent playtime she tore a cardboard flap out of her board book and examined it, trying different grips and holding it from different angles as she watched how it cut the air. Then, brandishing her precious flap, she went to work. She wielded it with a scooping motion to lift other flaps in the book, and later, to turn the book pages themselves. After that, she descended on her toy box with the flap. She used it to wipe her blanket, poke her stuffed animal, and finally scrape its face like she was giving it a close shave.

Although my daughter’s fun with flaps may seem aimless, it had an important purpose. Through experimentation and observation, she was learning how two objects can interact and how such interactions are affected by object shape, configuration, and pliability. Such details are so well known to adults that we forget there was anything to learn. But consider how often we use objects against one another. We hammer nails, rake leaves, and staple pages. When using scissors, we must apply different levels of force to cut through paper versus cardboard or fabric. When lifting a pan with a potholder, we must adjust our grip depending on the weight of the pan and whether we are lifting it by the base, side, or handle. We must know the subtle differences between holding a sponge to wash a glass and using a towel to dry it, and we must do each deftly enough that our glassware comes out clean and intact at the end.

There are also countless tools we create on the fly every day. When you use a magazine to nudge your cell phone within reach or flip a light switch with a book because your hands are full, you are devising novel tools to fit your momentary needs. To do this, our brains must store extensive knowledge about the properties of household objects. Through experimentation, like the kind my daughter is doing, we learned to predict how objects will interact and to capitalize on those predictions.

So far I’ve described the value of tools in terms of what they can do: push, pull, gather, polish, lift, etc. But there is another side to tool use that may play a role in my daughter’s little experiments: sensory information gleaned through the tool. As I watched her probe one object with another, I was reminded of research described in Sandra and Matthew Blakeslee’s book The Body Has a Mind of Its Own. The book discussed neurons in the parietal cortex that are tuned to the sight or feel of objects near a particular body part. For example, cells representing your right hand would fire if something touched your right hand, if you saw an object near your right hand, or both. Neuroscientists have discovered that experience using a tool can change the properties of these cells in monkeys (and therefore likely in us as well). They found that if monkeys used a rake to gather goodies otherwise beyond their reach, the parietal neurons that had responded to objects around the hand now fired for items located anywhere along both the hand and the rake it held. In a sense, object manipulation can temporarily extend certain neural body representations to include the tools we wield. The Blakeslees suggest that this may be how a blind person learns to perceive the contour of items encountered at the tip of his cane. In effect, the cane and the hand are one.

For now, our house is filled with smashing, scraping, banging and bending as our baby descends on toys and her parents’ belongings alike. In the midst of such havoc, it’s good to know that the destruction is part of a crucial learning process. And someday, once it slows down, I can buy her a new board book with all the flaps intact.


Photo credit: zzpza

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