Poker Neuroscience: On Neural Tells

71949406In poker, a player can gain an advantage if she can detect tells, subtle behaviors from other players that communicate the strength (or weakness) of their hands. Tells are not always reliable (e.g., clumsiness could be misinterpreted as anxiety about a bad hand) so veteran players use them cautiously.

In fact, it is hard to find a behavior that, on its own, predicts what someone is thinking. It is almost always a collection of behaviors, persistent across time and situations, that suggest a psychological state. Wouldn’t you be more convinced that someone loved you if they expressed this emotion in 100 ways instead of one? Individual behaviors are rarely good tells.

Yet neuroscience commentators often claim to write about neural tells: individual neural measurements that are highly reliable indicators of psychological variables like love (e.g., the oxytocin myth). But neural tells are Procrustean beds because, as I explain below, they ought to be significantly less reliable than behavioral tells.

Levels of Analysis

Psychological variables, like love, cannot be measured directly (after all, what is love?). Scientists simply search for tells, measurable variables that ought to correlate with the psychological variable. For example, the number of poems a couple write each other can be a tell of the strength of their love. But the correlation between the psychological variable and the tell weakens when these two variables exist in different levels of analysis.

For instance, brain activity can be measured at multiple levels of analysis. At an electro-physiological level, scientists can measure voltage changes that follow neural activity. At a hemodynamic level, scientists can measure oxygen level changes in the blood around active neurons. In this example, brain activity is examined at one of two levels of analysis.

Mixed Levels…

A scientist can mix levels of analysis. She can hypothesize about electrophysiology but measure hemodynamic activity as a tell. For example, she can use functional magnetic resonance imaging (fMRI) to measure oxygen concentration changes in the brain’s blood, but hypothesize that these changes reflect fluctuations in the brain’s electrical activity.

Luckily for her, electrical and hemodynamic activity are highly correlated (Logothetis & Wandell, 2004): the presence of one very often indicates the presence of the other. In turn, hemodynamic activity is a great tell for neural activity. Unfortunately, this is not the case in most situations that involve hypotheses and variables that mix levels of analysis.

…Make Tells Less Reliable

Variables often lack one-to-one relationships across levels of analysis. For example, love (psychological level) cannot be mapped to a single action (behavioral level). No behavior by a person indicates, always and exclusively, that she feels in love. Using this logic, neuroscience commentators should not expect to find highly reliable neural tells.

Most likely, it is a collection of neural measurements that should predict behavior and psychological variables. A variable in a higher level of analysis is almost always comprised of multiple variables in a lower level of analysis. So even a single emotion like love ought to have a complicated neural basis that is constituted by more than one neural measurement.


  • Neuroscience commentators claim to write about neural tells, individual neural measurements that are highly reliable indicators of psychological variables
  • But variable relationships across levels of analysis (behavioral to psychological, neural to psychological) are not one-to-one, making neural tells unlikely to exist
  • More often than not, it should be a collection of neural measurements that, together, predict psychological variables

The Human Brain Is Complex

PSM_V27_D079_Fissures_and_convolutions_of_the_human_brainScientists constantly marvel at the intricacy of the human brain, “the cathedral of complexity” (Coveney & Highfield, 1995, p. 279). Here, I share some facts about the brain to make clear its complexity and, in turn, the difficulty that neuroscientists face in understanding it.

Size and Weight

The average human brain is a small, lightweight object, measuring about 73 in3 (1,200 cm3; Cosgrove, Masure, & Staley, 2007) and weighing about 3.3 lb (1.5 kg; Herculano-Houzel, 2009). But these summary statistics belie the significant variability in brain size and weight across individual people. For example, brain size differs by demographic attributes like age, race, sex, and social class (Rushton & Ankney, 1996).

Cortical Shape

The brain’s cortex is shaped in gyri (ridges) and sulci (fissures). The organization of gyri and sulci show significant variability between brains (Ono, Kubik, & Abernathey, 1990and even between hemispheres in the same brain (Brett, Johnsrude, & Owen, 2002). Moreover, not all cortical regions show the same extent and type of variability (Thompson, Schwartz, Lin, Khan, & Toga, 1996).


The brain is composed of approximately 170 billion cells, about half of which are neurons; the rest are glial cells (Azevedo et al., 2009). Neurons communicate information with electrical and chemical signals (Purves et al., 2001). Glial cells serve many functions, from the production of neurotransmitters to maintenance of the blood-brain barrier (Oberheim, Wang, Goldman, & Nedergaard, 2006).


The brain’s neurons form a densely-connected network with connections in the order of 1 quadrillion (1015; Murry & Sturde, 1995). The strength and existence of many of these connections are not fixed (Sporns, Tononi, & Kötter, 2005); they change across development as a function of normal maturation and specific experiences (Holtmaat & Svoboda, 2009).


Neurotransmitters, of which more than 100 have been identified, help neurons communicate information (Purves et al., 2001). The amount and behavior of these chemicals varies across individual people, including systematic differences as a function of age (Rosene & Nicholson, 1999), sex (Zaidi et al., 2010), and mental health (Charney, Buxbaum, Sklar, & Nestler, 2013).

The Brain Does Not Light Up

No technology in recent history has played a bigger role in increasing our knowledge of the human mind than functional magnetic resonance imaging (fMRI). For this reason, findings from experiments that use fMRI receive significant media attention. As a scientist who used this technology, I am thrilled by this development.

controlling-the-brain-with-light_1Unfortunately, media reports about this research use language that prevents readers from understanding results from this work accurately. One of the worst offenders in this category is the phrase “lights up,” which neuroscience commentators insist on using to describe fMRI findings. For example, a reporter might say that the amygdala “lights up” when we feel fear or that the prefrontal cortex “lights up” when we make financial decisions.

This phrase gives the impression that brain regions are dark, silent creatures that wait patiently for a person to perceive or think about the right thing so that they may do their job. This mistaken impression not only misrepresents what fMRI does, but it also makes findings from this research difficult to interpret. Consequently, people cannot be appropriately critical of these discoveries.

The Importance of Differences

FMRI allows scientist to study the brain by measuring changes in its blood activity. Oxygenated blood rushes to a brain region after its neurons fire. When fMRI detects this hemodynamic response, scientists infer that the brain regions in which they took place experienced significant neural activity. This is akin to seeing someone in a gym drinking water and inferring that this person was working out.

However, brain regions are more like gym goers who are constantly drinking water, but who drink more after particularly heavy exercise. Blood courses through the arteries of every brain region at all times, but increased levels of oxygenated blood will rush to certain regions after perceiving or thinking about some stimuli more than others.

By understanding the stimuli differences that correlate systematically with changes in oxygenated blood in a brain region, scientists can start to reveal brain function. The phrase “lights up” misses this emphasis on relative, rather than absolute, brain activity. Consequently, fMRI findings cannot be communicated to the public appropriately.

An Example

For example, imagine that a group of scientists has participants in an fMRI study view images of faces in some cases and images of objects in others. These researchers find a brain region that shows higher levels of oxygenated blood after viewing faces instead of objects. In fact, two different groups of scientists discovered such a brain region (Kanwisher, McDermott, & Chun, 1997; McCarthy, Puce, Gore, & Allison, 1997) in the fusiform face area (FFA).

A headline reporting that FFA “lights up” to faces would rob the real finding of meaning. Oxygenated blood always courses through this brain region so the headline would be trivial. What was so important about the discovery of FFA was the fact that this brain region shows more changes in blood activity during the perception of faces than objects.

This result suggested that the way in which the brain perceives the world visually is organized along categories and that faces form one such category. More than a decade of additional research provides additional support for this view (Kanwisher & Dilks, 2013).


In fMRI research, the devil is in the differences: Differences in the stimuli shown to participants are associated with differences in brain activity. Scientists gain insights into the function of a brain region by understanding how stimuli differences correlate with changes in its blood activity.

This important point is lost on neuroscience commentators who write that brain regions “light up.” Though this phrase may help to distill complicated findings into simple headlines, it comes at a significant cost: A public who misunderstands the important and exciting findings that are slowly, but surely, helping us to understand the human mind.

When you read media reports about an fMRI experiment, be skeptical about a brain region that “lights up.” Ask whether you have information about which differences in brain activity were studied in the experiment. Consider what you think these differences might reveal about how the human mind works. Does your interpretation of the results align with the one proposed by the journalist and the scientists?

“Lights up” is by no means the only phrase that misrepresents fMRI research, but it is one of the most pervasive. If you read journalism about this neuroscience with a critical eye that goes beyond brain regions with light switches, then you will have a greater understanding of how these experiments are changing the way in which we understand ourselves.

Neuroscience Advice From Barack Obama

5f82dfd897344402913ea1834a6dc9feThe United Hemispheres of the Brain

In his keynote address at the 2004 Democratic National Convention, then-Illinois State Senator Barack Obama declared that “there is not a liberal America and a conservative America; there is the United States of America.” Obama argued that the liberal-conservative dichotomy is a Procrustean bed: an erroneous belief that the political differences between Americans overwhelm the similarities that unite them.

The myth that people are either right- or left-brained is a similar Procrustean bed because it espouses a simplistic dichotomy that distorts a more complicated reality. Psychology and neuroscience have shown repeatedly that there is not a right brain and a left brain; there are the united hemispheres of the brain. Those who would have you believe otherwise are misinformed, neuroprofiteers (more on them in a future post), or both.

Psychology Myth

The myth holds that there are two types of people in the world. One type includes people who look like engineer stereotypes: they think analytically, prefer careful, deliberate planning, and take a reasoned, logical approach to life. The other type includes people who look like poet stereotypes: they think creatively, act spontaneously, and have a carefree, open-minded perspective about things.

Unfortunately for this typology, decades of scientific research on human personality paint a different picture: personality is comprised of five dimensions (John, Naumann, & Soto, 2008). Unlike the myth, these dimensions, called The Big Five, do not suggest a dichotomous typology. This research suggests that there are plenty of analytical thinkers who act spontaneously; traits like these are not anti-correlated.

Neuroscience Myth

But the myth goes even further. It states not only that there are two types of people in the world, but also that this typology is caused by differences in brain function. According to the myth, analytical people rely more on the left hemisphere of their brain whereas creative people make greater use of the right hemisphere of their brain.

This hypothesis supposes that the left and right hemispheres serve different functions or operate on information in dissimilar ways. Though some hemispheric differences in brain function and information processing exist (Toga & Thompson, 2003), the existing evidence does not support the drastic personality dichotomy suggested by the myth (Hines, 1987).

A Joint Effort

The two hemispheres are always working together to allow us to act, think, and feel. For example, each hand is controlled by the motor cortex in the opposite hemisphere (i.e., the right motor cortex works the left hand). Similarly, the somatosensory cortex in each hemisphere processes touch from one hand. To a large extent, brain symmetry reflects body symmetry and supports the use of a bilateral body.

Coordination between the right and left side of the brain is possible because the two hemispheres are united by a thick bundle of neurons called the corpus callosum. These neurons ensure that information flows freely from one side of the brain to the other. The left hemisphere is never incommunicado from the right hemisphere. (However, the corpus callosum can be removed surgically; one such split-brain patient is shown in this video).

Inter-hemispheric collaboration is even necessary to support abilities that are thought to use one hemisphere exclusively. For example, though language is often associated with the left hemisphere, neuroimaging studies show that both hemispheres are likely to be involved in language processing (Vigneau et al., 2006). Even a person who loses the left hemisphere during childhood can acquire good language abilities (Smith & Sugar, 1975).


  • People are not right- or left-brained
    • Psychology shows that personality is composed of five dimensions that are inconsitent with the typology proposed by the myth
    • Neuroscience shows that the brain hemispheres work together, performing similar tasks and sharing information to allow us to act, think, and feel
  • Individuals and organizations who evangelize otherwise are misinformed and/or want to profit from people’s misunderstanding of neuroscience


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Oxytocin, A Conspiracy Story

Conspiracy theories maintain that a small group of people can not only change the world, but that they can do so in such a way that virtually everyone is unaware of their role in shaping history. These theories are criticized, in part, because they assume that too few people can get away with too much.

conspiracy-theory-alertNeuroscience commentators have adopted conspiracy-like theories about the molecule oxytocin. These theories hold that evolution has found a way to make this molecule solely responsible for complex psychological phenomena like altruism, happiness, love, morality, or trust. Can a single molecule really get away with so much?

As is often the case, the science is more complicated than its commentary. A hormone that acts as a neuropeptide in the mammalian brain (Landgraff & Neuman, 2004), oxytocin plays many roles in reproduction and other social behaviors for many species, including ours (Gimpl & Fahrenholz, 2001MacDonald & MacDonald, 2010).

Simplistic accounts of oxytocin’s function are Procrustean beds that suffer from four serious problems.

Problem 1: What Exactly Does Oxytocin Do?

Terms like altruism, happiness, love, morality, and trust are not synonyms (e.g., love is a feeling whereas morality refers to beliefs about right and wrong). This means that either oxytocin is the molecule behind only one of these concepts, or it plays a role in something that is present in all of them (e.g., the feeling of attachment).

In either case, neuroscience commentators should not rush to label oxytocin as the molecule of [insert complex psychological phenomenon] with such confidence.

Problem 2: Inconsistent Findings about Oxytocin

The positive effects of oxytocin in experiments are not always consistent. In fact, most studies only find evidence of these effects in some people under some circumstances (Bartz, Zaki, Bolger, & Ochsner, 2011). For example, oxytocin does not increase participants’ trust of individuals who appear untrustworthy (Mikolajczak et al., 2010).

Some studies find that oxytocin has negative effects (Bartz et al., 2011), like defection (Declerck, Boone, & Kiyonari, 2010), envy (Shamay-Tsoory et al., 2009), and in-group favoritism, the preferential treatment of the groups to which we belong (De Dreu, 2012).

Problem 3: Oxytocin Does Not Work Alone

Oxytocin is part of a complex brain chemistry. This molecule regulates social behavior and cognition alongside the neuropeptide vasopressin (Donaldson & Young, 2008Carter, Grippo, Pournajafi-Nazarloo, Ruscio, & Porges, 2008). For example, individual differences in a vasopressin receptor correlate with variability in altruism displays (Knafo et al., 2007).

In fact, vasopressin and oxytocin have many similarities. They share a receptor family (Peter et al., 1995) and work in the same neural pathway (Ebstein et al., 2009). They were likely created by the duplication of the same ancestral gene (Gimpl & Fahrenholz, 2001) and the same gene may regulate their levels (Ebstein, Knafo, Mankuta, Chew, & Lai, 2012).

Problem 4: Negative Consequences of Oxytocin Hype

Science writer Ed Yong has argued that commentary that oversells our understanding of oxytocin can lead to its misuse by a misinformed public. The alleged prosocial effects of this molecule have led parents to give oxytocin to their autistic children (Yong, 2012a, 2012b). This is troubling because the side effects of oxytocin are not fully understood yet.


  • Neuroscience commentators claim incorrectly that oxytocin is the molecule behind complex psychological phenomena like altruism, happiness, love, morality, or trust
  • These simplistic accounts suffer from four serious problems
    1. Inconsistency with each other
    2. Dismissal of conflicting scientific findings
    3. Oversimplification of brain chemistry
    4. Dangerous consequences from a misinformed public


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The Brain Is Not That Hard

Promiscuous Teleology

From childhood, we show a proclivity for promiscuous teleology, readily ascribing function and purpose to the objects around us (Kelemen, 1999). We view an apple primarily as nourishment; an apple tree as a source of apples first and foremost. We are wont to believe that most every thing, natural or artificial, is there for a special reason; designed with a larger goal in mind.

This teleological bias is often present in neuroscience commentary. The finding that a brain region shows more neural activity when people (often adults) do X than when they do Y is taken as evidence that our brain is “hard-wired,” or evolved, for the purpose of doing X. Using this logic, neuroscience commentators claim that psychological phenomena ranging from altruism to racism are built in to our neural hardware from birth.

Evolution versus Experience

The brain is by no means a blank slate at birth, of course; it is the product of evolution (Creely & Khaitovich, 2006). But genes are not destiny; the experiences that we have and the environments that we navigate shape how our brains function in critical ways. For example, the brains of blind humans repurpose cortical regions typically involved in vision for other senses, like audition and touch (Pascual-Leone, Amedi, Fregni, & Merabet, 2005).

Superman_Batman_by_Clayton_HenryConsequently, the finding that a brain region shows more neural activity when people do X than when they do Y need not mean that this brain region evolved to do X; there may be no “hard-wiring” at work. Our brains can tell Batman and Superman apart, but it does not follow that we evolved an ability to identify super heroes. What we experience (e.g., comic books and action movies) has an important influence in how our brains function. This neuroplasticity helps us adapt successfully to an environment that changes constantly (van Praag, Kempermann, & Gage, 2000).

Hard Wires Require Hard Evidence

Neuroscience commentators who rush to evolutionary interpretations of neuroscience studies are often making a Procrustean bed. They reach conclusions that say more about their promiscuous teleology than about what can reasonably be induced from the data at hand. It is difficult to show that an element of our psychology is the product of evolution.

For example, to show conclusively that laughter is “hard-wired” in the brain would require a deprivation experiment: does a person raised in isolation laugh spontaneously? Barring such an unethical study, it would require converging evidence from scientific experiments that examine development (do infants laugh before they hear laughter?), culture (do people in all cultures laugh?), and genetics (can we identify genes that, when expressed, allow us to laugh?) (Nota bene: See here for an interesting discussion on the evolution of laughter.)


  • Neuroscience commentators often interpret data from neuroscience studies as evidence that different psychological phenomena are “hard-wired” in the brain
  • Such evolutionary explanations rarely follow from the results provided by these studies
  • Claims about the evolutionary status of a psychological phenomenon are difficult to make because they require converging evidence from different scientific disciplines


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Why Procrustean Neuroscience

Procrustean Beds

illustration-15The Greek myth goes that Procrustes was a man who had a place between two cities. He invited travelers who were passing by to stay in his iron bed. When the guests were too short for the bed, he would stretch them out to fit it.

Nassim Nicholas Taleb recounts this myth in The Bed of Procrustes to argue that people deal with a complex world by perceiving it with overly simplistic and often incorrect theories. In the same way that Procrustes fit people to a bed, Taleb contends that we fit data to a theory. In both cases, the wrong variable is modified.

Fitting data to a theory is bad for two reasons. First, the theory prevents its user from understanding the data properly. A neuroscientist cannot fully understand the role of the cerebellum in speech if her theory tells her that the cerebellum plays no role in speaking.

Second, people forget that a theory is always a working theory: a work in progress that needs updating when new data begins to disconfirm it. A theory may state that the cerebellum is not involved in speech production, but the theory may be completely wrong.

Neuroscience Commentators

Neuroscientists are scientists who study the nervous system. In this blog, I will write mostly about neuroscientists who study the function of the human brain with tools like functional magnetic resonance imaging. I do this not only because I was trained in this area, but also because the study of human brain function may be the area of neuroscience that lends itself the most to fitting data to bad theories. I explain why in a future post.

I define neuroscience commentators as those individuals who communicate findings from neuroscience studies to the general public. Most commentators are journalists who write about this science, but they also include scientists who write in the popular press.

Epistemic Humility

Too many neuroscience commentators have Procrustean beds. They take studies with specific, tentative findings and draw general, confident inferences about psychology (how we act, feel, and think) that are unwarranted by the data. At best, this misrepresentation of science is ignored and forgotten. At worst, it is accepted by the public and exploited by neuroprofiteers (more on them in a future post).

Neuroscience has taught, is teaching, and will teach us much about psychology. But the brain is complex, neuroscientific tools are imperfect, and our knowledge is limited, so progress will be slow and tentative. Neuroscience commentators should acknowledge these facts and approach their subject aware of the limitations in what they know and how they know it; they should show epistemic humility.

In Seven Psychologies, Edna Heidbreder writes that “psychology has acquired … the skepticism that for science is the beginning of wisdom. It knows that it knows little and that that little is tentative.” Epistemic humility from neuroscience commentators should show that neuroscience is just as wise as psychology.


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