Jamie Hale

Jamie Hale

Wednesday, July 11, 2018

A New Understanding of the Human Brain: The Human Advantage

by Jamie Hale

College students are taught that the human brain consists of 100 billion neurons.  This claim can be found in numerous textbooks.  College instructors often promote the 100 billion neuron claim.  This claim is also promoted by widespread media sources. If you have read much about the brain or engaged in dialogue regarding the human brain there is a good chance you have encountered this statement: seemingly, this is general neuroscience- basic stuff.    When I was a graduate student this number was accepted without question.  What is the original source for this number?

Another claim that is often made regarding brain science is that there is "ten times more glia (glia often referred to as neuron support cells) than neurons in the human brain."  Is there an original source for this number?  Is there evidence for 1 trillion glia in the human brain?
Herculano-Houzel addresses both of these topics in her book The Human Advantage: A New Understanding of How Our Brain Became Remarkable (2016).  She provides evidence to refute the 100 billion neuron and the 1 trillion glia claim. Her research has led to a change in teaching neuroscience and has driven pop and scholarly publications to make changes. 

The Human Advantage: In Review

Suzana Herculano-Houzel, is the author of The Human Advantage.  She is a former associate professor and head of the Laboratory of Comparative Anatomy at the Federal University of Rio de Janeiro.  She is the author of six books on the neuroscience of everyday life.  She is a former writer and presenter of the TV series Neurologica.  Currently, she resides at Vanderbilt University.
How do humans have such tremendous cognitive abilities?  Herculano-Houzel argues that human are remarkable, but they are not special in light of evolution.  Human brains follow the rules of primate evolution.  Primates have an advantage over other mammals regarding brain structure;   primates brains have evolved in a way that allows neurons to be added to the brain, without the large increases in average cell sizes seen in other mammals.  Primate brains have evolved differently than those brains of other animals.  As an example, cows and chimpanzees have brains that are similar in mass, but the chimpanzee can be expected to have at least twice as many neurons as a cow.  Human brains are scaled up primate brains.  Contrary to the popular claim that the human brain is larger than can be expected for body type (expressed as encephalization quotient), the author argues the number of brain neurons as a function of body mass is what can be expected for a non-great ape primate.

Neuroscientists, in the past, thought that the human brain is large relative to the size of the body that contains it, when directly comparing to brain and body size of great apes.  If our body is smaller, then our brain should be smaller, and yet it is three time larger in terms of mass.  However, Herculano-Houzel's data show that when great apes are excluded humans show the same relationship between their body mass and number of brain neurons as that of other primates.  In the first decade of the twenty-first century, systematic comparisons relative to the encephalization quotient, started being made of cognitive abilities among nonhuman primates, and of self control abilities among birds and mammals.  The general finding was "simple absolute brain size was a much better correlate of cognitive capabilities than the encephalization quotient.  It was back to square one.  If the human brain is not the largest, then how can it be the most capable of them all?" (Hercualno-Houzel, 2016, pp. 16-17.).  The human brain is just what can be expected for a primate brain that has evolved to adapt to human conditions.  The primary mechanism responsible for human cognitive abilities is the number of neurons in the cerebral cortex.  The human brain has more neurons in the cerebral cortex (16 billion) than any other animal, even when the animal (African elephant) has 257 billion brain neurons.

What is the original source for the - 100 billion neurons in the human brain assertion?  Herculano-Houzel asked senior neuroscientists and no one was able to point her to the original source. After an extensive search through the scientific literature she wasn't able to find a single source supporting the 100 billion neuron claim.  According to Herculano-Houzel, Eric Kandel (Nobel Laureate), co-author of Principles of Neural Science, couldn't provide an original source for the claim, even though the claim was made in Principles of Neural Science (a book Kandel co-authored).  When asked about the claim, Kandel responded saying he wasn't responsible for the chapter containing the 100 billion neuron claim.
Is there evidence for 1 trillion glia in the human brain?   Herculano- Houzel reports she couldn't  locate any research to support the claim- 1 trillion glia in the human brain.  Both of these claims (100 billion neurons and ten times more glia) are often taken as fact.   Accepting information as fact, even though it is not  supported by evidence is problematic; specifically problematic as it is odds with a central tenet of science; scientific data is based on evidence.  A paper published by Herculano-Houzel and colleagues titled "Equal Numbers of Neuronal and Non-Neuronal Cells Make the Human Brain an Isometrically Scaled-Up Primate Brain," which is now a heavily cited paper, was rejected by high ranking journals including Nature, Proceedings of the National Academy of Sciences of the U.S.A., Neuron and the Journal of Neuroscience. The paper was eventually published in the Journal of Comparative Neurology.

Houzel developed a method called the "isotropic fractionator" that allowed her to create what she calls brain soup?  The method allows dissolving only cell membranes, but not nuclear membranes (each neuron consists of one nuclear membrane), therefore producing brain soup with free-floating nuclei.  These nuclei are relatively easy to count by sampling tiny amounts of the soup.  All the nuclei from all of the cells are stained blue, collected and counted.   In the book she provides a description of what went into developing the technique.  The first attempts to use the method led to the destruction of some of the nuclei. Early attempts involved testing the preparation after a few hours of fixation. In order for the all of the nuclei to remain intact longer preparation times were required. It was finally  established that after approximately two weeks of fixation the nuclei would all stay in place during testing.  Other researchers have used this method.  Christopher von Bartheld, from the University of from the University of Reno, and Jon Kaas, from Vanderbilt University have shown this method to be faster, more reliable and easier to apply than stereology, which was commonly used in the past. 
Results, after using the isotropic fractionator, indicate the human brain has an average of 86 billion neurons and 85 billion non-neuronal cells (glia and endothelia- cells composing blood vessels)   For people who like to point out that "86 is close to 100" and who claim the 100 billion is reasonable as an order-of-magnitude estimate, Houzel asserts, an entire baboon brain contains 11 billion neurons.  Fourteen billion is not a small number of neurons.

The author concludes that the human brain is remarkable due to the number of neurons in the cerebral cortex (approximately 16 billion) and secondly it is remarkable thanks to cooking, which allowed humans to escape the energetic limitations of a raw food diet, that limits other animals to less cortical neurons.  Chapter 11 provides detailed information on how cooking contributed to the human brain.      
The book appeals to a large audience.  Even though sections of the book might be difficult for some to read, with the appropriate effort the information is accessible for most people.  The author points out that some of her earlier work was met with resistant.  It shouldn't be surprising that some may have a problem accepting views that challenge what they thought to be neuroscience fact for so many years.  I highly recommend this book. Herculano-Houzel is a major player in neuroscience.

Title: The human advantage: a new understanding of how our brain became remarkable / Suzana Herculano-Houzel.
Description:  Cambride, MA: The MIT Press, 2016
ISBN 9780262034258

Monday, June 25, 2018

Why Science Matters

By James Randi
Visit Randi’s site at www.randi.org 

Science is not the mysterious, distant, smoking-test-tube sort of a priesthood that many imagine it to be. Rather, it is simply an organized, formal method of “finding out.” Science works. We’re all much better off for having vaccines, rapid international travel, fast access to information, instant communication; and improved, safer nutrition —all direct results of what scientists have discovered about how our real world works. And have no doubt about it: we’re living in a real world, one that doesn’t really care about our comfort or even our survival. We have to see to these matters, and we’ve gotten to be very good at this. 

That’s due to what we call “science.” 

There are those who try to disparage efforts by science to discover the secrets of the universe, preferring to depend on mythology like faith healing, charms, incantations/prayers, and various other magical motions. Science looks at the evidence, evaluates it, proposes a likely scenario that can accommodate it —a theory —and then tests that idea for validity. 

But science doesn’t really discover many cold, hard, facts. Rather, it discovers statements that appear to explain certain observed phenomena or problems. These statements –s=ut+½ at², for example –are tested endlessly. Should they fail, they are either re-written or scrapped.
You just may have recognized that formula above. It’s a discovery made by Sir Isaac Newton, and expresses the variables of the situation in which a cannonball is dropped from a convenient Leaning Tower in Italy. The formula works quite well, except when the cannonball is replaced by something the size of an electron or a galaxy. Then, it fails. 

Does that mean that the eminent scientist Newton was wrong all these years? Did science fail? No. Within the parameters in which Sir Isaac worked, he was right; outside of those limits, quantum physics takes over, and all’s right with the world once more.
This self-correcting feature of science is not a weakness. It’s one of the most important advantages of the discipline. Scientists learn something new, when they’re wrong. And they correct their findings, and we get closer to the truth. Science has no dogmas…The bottom line: Science works, we need it, and it improves our lives and the lives of those dear to us. What more can we ask?  - This article is an excerpt from In Evidence We Trust: The Need for Science Rationality and Statistics

Reviews of  In Evidence We Trust
Jamie Hale: In Evidence We Trust
Recommended Resources-In Evidence We Trust

Friday, May 18, 2018

Negative Consequences of Irrationality

Rationality is rooted in good decision making; it reflects what is true (epistemic rationality) and what to do (instrumental rationality). Rationality, in terms of cognitive science, reflects appropriate goal setting, maximizing goal attainment and acquiring evidence based beliefs: beliefs congruent with reality. (Stanovich, West & Toplak, 2016). On occasion, someone asks "what is reality?." This is a rhetorical question used when ones belief or assertion is unlikely, unrealistic; it drastically deviates from evidence, is refuted with evidence, etc.. . Most have some sense of reality, that is they refer to a model-dependent reality (mental representation of reality, conceptualization) to live their lives (Hawking & Mlodiknow, 2010).  They only pose the reality question in times of need (when they are likely wrong). If no sense of reality can be achieved a structured, meaningful life will be hard to live.  Many individuals are inconsistent with the criteria needed in order to label a belief, claim or phenomenon as real. That type of inconsistently is not the focus of this article; I will address this later.

Irrationality may lead to an array of negative outcomes: using the ineffective medical treatments because of failure to think of alternative causes; poor financial decisions because of overconfidence; misjudging environmental risks because of vividness, acquisition of contaminated mindware of Ponzi and pyramid schemes, be wrongly influenced in their jury decisions by incorrect testimony about probabilities, damage to intellectual vales and continue making many other of the poor decisions.

Why do we act and behave irrationally? Two broad categories contribute to this problem: a processing problem and a content problem. When choosing the cognitive strategies to apply when solving a problem we generally choose the fast, computationally inexpensive strategy. Although we have cognitive strategies that have great power, they are more computationally expensive, are slower, and require more concentration than the faster cognitively thrifty strategies. Humans naturally default to the processing mechanisms that require less effort, even if they are less accurate. Individuals with high IQs are no less likely to be cognitive misers than those with lower IQ's. A second source of irrational thinking-content problem-can occur when we lack specific knowledge to think and behave rationally. David Perkins, Harvard cognitive scientist, refers to "mindware" as rules, strategies, and other cognitive tools that must be retrieved from memory to think rationally (Perkins, 1995; Stanovich, 2009). The absence of knowledge in areas important to rational thought creates a mindware gap. These important areas are not adequately assessed by typical intelligence tests. Mindware necessary for rational thinking is often missing from the formal education curriculum.It is not unusual for individuals to graduate from college with minimal knowledge in areas that are crucial for the development of rational thinking.

Rational thinking skills are learnable, and with the development of rational thinking skills  better judgment and decision making in everyday life may follow.  From an interview with the Stanovich research lab:

Do you think a good starting point [in regards to learning of rational thinking] would be becoming educated on basic logic?

Basic logic would be part of a rational thinking skills curriculum, but not necessarily the first part. Again, rational thinking in cognitive science encompasses decision theory, epistemic rationality, and many areas beyond simply the study of basic logic in philosophy 101. It is very important to understand that rational thinking in cognitive science is rooted in good decision-making. Good decision making skills and good skills of knowledge acquisition do have logical thinking as one subcomponent. But there are many subskills that are even more important than logic. The subskills of scientific thinking, statistical thinking, and probabilistic reasoning, for example. Many of these are listed in the books that we will recommend here.

Baron, J. (2008). Thinking and deciding(Fourth Edition). Cambridge, MA: Cambridge University Press.

Hastie, R., & Dawes, R. M. (2001). Rational choice in an uncertain world. Thousand Oaks, CA: Sage. (a new 2010 edition is just out)

A recent chapter of ours contains a large number of citations to successful attempts to teach the skills of rational thought:

Toplak, M. E., West, R. F., & Stanovich, K. E. (2011). Education for rational thought. In M. J. Lawson & J. R. Kirby (Eds.), The quality of learning. New York: Cambridge University Press.” 

Thursday, January 11, 2018

Peer Review is not the Antidote

 In the Peer Review Process a paper is submitted to a journal and evaluated by several reviewers (often reviewers are individuals with an impressive history of work in the area of interest-that is, the specific area that the article addresses).  After critiquing the paper the reviewers submit their thoughts to the editor.  Then, based on the commentaries from the reviewers, the editor decides
whether to publish the paper, make suggestions for additional changes that could lead to publication, or to reject the paper. 

Single Blind and Double Blind Reviews

In Single Blind Reviews authors do not know who the reviewers are.  In Double Blind Reviews authors do not know who the reviewers are, nor do reviewers know the identity of the authors.  In many fields Single Blind Reviews are the norm, while in others Double Blind Reviews are preferred.
“Peer review is one way (replication is another) science institutionalizes the attitudes of objectivity and public criticism.  Ideas and experimentation undergo a honing process in which they are submitted to other critical minds for evaluation.  Ideas that survive this critical process have begun to meet the criterion of public verifiability” (Stanovich, 2007, p. 12).

Criticisms Peer Review Process

Reviewers find it hard to remain Purely Objective due to their own education, experience and biases

The process is slow Critics point out, and this may deter submission of quality papers  

There are many examples of poor research published in peer-reviewed journals, which indicates the peer review process is often unsuccessful in preventing the publication of  bad science

Sometimes good research is not published, especially when findings are not statistically significant.  Publication bias is problematic and demonstrates confirmation bias

Reviewers are not always knowledgeable regarding contents they are reviewing (I have been asked to review papers that consist of contents that was outside my area of knowledge)

Lack of agreement and communication among reviewers

Reviewers tend to be highly critical of articles that contradict their own views, while being less critical of articles that support their personal views (example of myside bias). Well-known, established scientists are more likely to be recruited as reviewers

Lacks standardized criteria, and criteria for publication demonstrates huge variability among scholarly publications.

Final word-Peer Review Process
The Peer Review Process is not perfect, but some researchers suggest  it is one of the best safeguards we have against junk science (Stanovich, 2007). When evaluating the worth of scientific data, in addition to whether it is published in a peer reviewed journal, it is important to take into consideration:  funding sources, study replication, study design, sample size, conflicting interest, sampling error, different measures of reliability and validity, reporting limitations and other possible criticisms of study (special concern with *statistical validity- often not acknowledged or understood). 

There are good studies that never get published in peer review publications, and low quality studies are published by peer review publishers.  It is erroneous to label a study, review, commentary, meta-analysis or any other scholarly papers as high quality based solely on peer review status. This over glorification of peer review pervades academia and pop science.      

* When researchers question a study’s statistical validity they are questioning issues relevant to how well the conclusions coincide with the results, represented as statistics. Interrogating statistical validity may include some of the following questions: If the study found a difference what is the probability that the conclusion was a false alarm?  If the study’s finding found no difference what is the probability that a real relationship went unnoticed?  What is the effect size?  Is the difference between groups statistically significant? Are the finding practically significant? What type of inferential stats were used to assess predictions? Could different statistical procedures have been used? How would different samples influence statistical findings?  Stats make use of samples; inferences about the population are derived from data collected in the study.  It is important to avoid an exaggeration of the findings, consider sampling error, consider external validity and consider the need for converging evidence, and what the finding indicate regarding a representation of the population.

Addendum- 2-9-18

from When Does Peer Review Make No Damn Sense:

"What sort of errors can we expect peer review to catch? ...I’m well placed to answer this question as I’ve published hundreds of peer-reviewed papers and written thousands of referee reports for journals. And of course I’ve also done a bit of post-publication review in recent years.

To jump to the punch line: the problem with peer review is with the peers.

In short, if an entire group of peers has a misconception, peer review can simply perpetuate error. We’ve seen this a lot in recent years, for example that paper on ovulation and voting was reviewed by peers who didn’t realize the implausibility of 20-percentage-point vote swings during the campaign, peers who also didn’t know about the garden of forking paths. That paper on beauty and sex ratio was reviewed by peers who didn’t know much about the determinants of sex ratio and didn’t know much about the difficulties of estimating tiny effects from small sample sizes.

OK, let’s step back for a minute. What is peer review good for? Peer reviewers can catch typos, they can catch certain logical flaws in an argument, they can notice the absence of references to the relevant literature—that is, the literature that the peers are familiar with. That’s how the peer reviewers for that psychology paper on ovulation and voting didn’t catch the error of claiming that days 6-14 were the most fertile days of the cycle: these reviewers were peers of the people who made the mistake in the first place!

Peer review has its place. But peer reviewers have blind spots. If you want to really review a paper, you need peer reviewers who can tell you if you’re missing something within the literature—and you need outside reviewers who can rescue you from groupthink. If you’re writing a paper on himmicanes and hurricanes, you want a peer reviewer who can connect you to other literature on psychological biases, and you also want an outside reviewer—someone without a personal and intellectual stake in you being right—who can point out all the flaws in your analysis and can maybe talk you out of trying to publish it.

Peer review is subject to groupthink, and peer review is subject to incentives to publishing things that the reviewers are already working on."

From: Evidence on peer review—scientific quality control or smokescreen?

"Summary points

  • Blinding reviewers to the author’s identity does not usefully improve the quality of reviews
  • Passing reviewers’ comments to their co-reviewers has no effect on quality of review
  • Reviewers aged under 40 and those trained in epidemiology or statistics wrote reviews of slightly better quality
  • Appreciable bias and parochialism have been found in the peer review system
  • Developing an instrument to measure manuscript quality is the greatest challenge" 

Even though not labeled as peer review, popular pubs often use peer review. That is, articles are reviewed by individuals that can be considered peers, suggestions are made regarding changes to article, and author responds and revises relevant to suggestions. So, the claim that only scholarly like "peer review" pubs involve reviewing and revising in accordance to others suggestions i incorrect. But, peer review journals, as a whole, publish higher quality information correct? Yes. To reiterate, the peer review process has strengths, but it has limitations, and it shouldn't be used "alone" as a marker of quality.

Read these:

Effects of  Editorial Peer Review

Effectsof Training on Quality of Peer Review