The TEDx Users Guide to Dr Caroline Leaf

On the 4th of February 2015, Dr Caroline Leaf gave her debut TED presentation, at TEDx Oakes Christian School, California.

Most TED watchers wouldn’t have heard of her before, but Caroline Leaf is a well-known name in western Christendom. She has spoken from pulpits on every continent. She’s authored one of the best selling books in the Christian market and has her own TV show on cable in the US. She’s followed by more than one hundred thousand people on Facebook, and she’s even run her own conference, with another in the pipeline. She’s a mega-star in the Christian world.

So who is this woman with the stiletto-heels and slick presentation? What was her training and background? How did she make it to the TEDx stage?

This aim of this post is to provide some context and background for those in the TED universe who have seen Dr Leaf’s TEDx presentation, and want some more information in assessing her TEDx debut, and indeed, the global Caroline Leaf phenomenon.

This review will be in four main parts: first I will give some basic information on Dr Leaf, I will compare Dr Leaf’s claims in her TEDx presentation to her published research results and some basic neuroscience, and lastly I’ll outline Dr Leaf’s general work and it’s accuracy compared to current science.


Dr Caroline Leaf was born and raised in South Africa, where she completed her school education and went on to attain the following degrees:

  1. Bachelors of Science (Logopaedics) – University of Cape Town 1985
  2. Masters in Audiology and Speech Pathology – University of Pretoria 1990
  3. Doctor Philosophiae (Communication Pathology) – University of Pretoria 1997 (

Officially, Dr Leaf is qualified as a communication pathologist (which is a specialized combination of Speech Pathology and Audiology – see also:

Dr Leaf worked for a number of clinics and school boards as a communication pathologist in the few years following the completion of her PhD (

Dr Leaf has written a number of articles for publication in minor journals (see Three of her papers were published in a small Medline indexed journal, “The South African Journal of Communication Disorders”. These are:

  1. “Mind-Mapping approach (MMA): a culture and language “free” technique”, 1993 (
  2. “The development of a model for geodesic learning: the geodesic information processing model”, 1997 (
  3. “An alternative non-traditional approach to learning: the metacognitive-mapping approach”, 1998 (

The journal happened to be edited by her supervisor and co-author, Dr Brenda Louw (see, though I’m sure the selection of her articles for this journal was purely on merit.

Dr Leaf states on a number of occasions that she is a “cognitive neuroscientist”, and “a scientific and Biblical expert in the power of the human mind”.Leaf Cognitive NeuroscientistAbout Dr Leaf

This is despite the fact that Dr Leaf:

  1. does not have formal qualifications in neuroscience,
  2. has not worked at a university as a neuroscientist,
  3. has not worked in any neuroscience research labs,
  4. has not published any papers in neuroscience journals, and
  5. has not had any formal theological training.

Given the weight of evidence, Dr Leaf would be better described as an academic speech pathologist and lay preacher rather than a cognitive neuroscientist.


Throughout her TEDx presentation, Dr Leaf repeatedly made reference to the results of her own research, suggesting that her pioneering work resulted in radically improved outcomes for the students involved in her research, and that her work with students one-on-one and through teacher education profoundly changed the learning of every student in her various programs.

For example, she said, “Well her IQ was 100 before the accident, it was 120 after the accident. So here with holes in her brain, and brain damage, she changed … she actually increased her intelligence. Now I’m pretty convinced at this stage, cause I’ve been working … besides her I’ve been working with lots and lots of other patients, seeing the same thing, when these students applied their mind, their brain was changing, their academic results were changing.”

Later she stated, “I wasn’t sure if this was going to have the same impact cause until this point I’d been working one on one. Well I’m happy to tell you that we had the same kind of results … The minute that the teachers actually started applying the techniques, we altered the trend significantly.”

And also, “I stand up here saying this with conviction because I have seen this over and over and over in so many different circumstances … in this country I worked in Dallas for three years in charter schools, and we found the same thing happening.”

However, her published results differ significantly from her claims.

The first research that Dr Leaf spoke of was of the sixteen-year-old girl who was the victim of a motor vehicle accident. This particular girl was Dr Leaf’s prime patient. The case study of this patient was presented in Dr Leaf’s unpublished Masters thesis, and was discussed in more detail in Dr Leaf’s paper, “Mind-Mapping approach (MMA): a culture and language “free” technique” [1], though it should be noted that no statistics were published in this paper, and on the third page of the article, Dr Leaf admitted that the result could actually have been spontaneous recovery rather than her own intervention.

Dr Leaf did further work within a number of schools for her PhD research. Dr Leaf compared the academic results for three schools for the years 1991 and 1992 to the results for 1993, during which she introduced her mind mapping approach (MMA). Generally, the results for 1993 were better than the results for 1992, which seems to indicate that Dr Leaf’s MMA training was effective. However, the results from 1991 to 1992 were already improving without her input [2: p182]. The difference in average marks between 1991 and 1992 was 1.76%, while the difference between 1992 and 1993 (the introduction of Dr Leaf’s MMA) was only 2.19%. If Dr Leaf’s program really was the cause of that improvement, then her program only resulted in a 0.43% improvement on average.

I have reproduced Dr Leaf’s original graph of the average overall results obtained in her PhD study. While Dr Leaf’s original graph makes her data look spectacular, when appropriately rescaled, the data looks quite ordinary.

Leaf1997 Thesis overall academic trends


At best, Dr Leaf’s program gave the already positive momentum of the students a gentle nudge.

However, it should be noted that her program may have also hindered some students. Dr Leaf notes in her analysis: “The results obtained indicate that in general the academic trend in the three primary remedial schools was altered with the introduction of the MMA methods in 1993. Furthermore, it appears that the most positive response occurred in phase one (grades 1 and 2, standard 1). A positive response also occurred in phase two (standards 2-4) but this change was just outside the significance level. Phase three (standard 5), by contrast, experienced negative effects with the introduction of the MMA methods.” [2: p181]

So to summarise, according to Dr Leaf’s own data, there was no clear benefit derived from her MMA program.

Dr Leaf then discussed her work in a number of charter schools that she performed in Dallas. This was part of testing of a program called the Switch On Your Brain 5-step learning process.

Dr Leaf claims that, “The Switch On Your Brain with the 5-Step Learning Process® was assessed in a group of charter schools in the Dallas. The results showed that the students’ thinking, understanding and knowledge improved across the board. It was concluded that The Switch On Your Brain with the 5-Step Learning Process® positively changed the way the students and teachers thought and approached learning.”

However, there has been no independent research into Dr Leaf’s Switch On Your Brain learning program or even the Geodesic Information Processing Theory, the theory Dr Leaf devised and on which the Switch On Your Brain program is based.

Dr Leaf published her own internal research into the program on her website. The project was a two year program involving teachers and students at a group of four schools in the Advantage Academy group in Dallas, Texas. This involved working with more than 150 teachers and 2000 students.

Despite her glowing self-assessment, Dr Leaf’s own published numbers suggest that the program is ineffective, or quite possibly a hindrance. For example, the graph below demonstrates the qualitative analysis of “content mastery” (which the paper describes as a combination of knowledge and understanding) for reading across all grades from 3rd to 12th, compared with the results from the previous year before the Switch On Your Brain was implemented. Dr Leaf omits a basic statistical analysis, but just by looking at the similarity of the scores, these results are more likely to be a chance effect, except for the 12th grade, where the previous cohort of students increased dramatically, where as the Switch On Your Brain cohort got slightly worse.

Screen Shot 2015-02-02 at 11.27.37 pm

Rather than blame her program, Dr Leaf simply shifts the blame to the teachers: “The few cases where we see drops can be linked to teacher knowledge, attitude and skills and is diagnostic.”

The full research paper that Dr Leaf published is available at if you wish to review the results for yourself.

The ineffectiveness of Dr Leaf’s program may be for many reasons, but I believe one is that it is built on a theory that relies on mind-mapping. Dr Leaf renamed her version of mind-mapping “The Metacog”, though it’s clear from her early academic work [1] that the Metacog and the Geodesic Information Processing Model [3] were based on the work of Tony Buzan. Buzan’s concept of mind-mapping has been used across multiple professional fields [4] and remains a valuable resource for brainstorming or gathering thoughts in a visual way. However, modern research (including a controlled trial within a primary school classroom environment) shows that mind mapping is a poor tool for learning [5-8].


Dr Leaf openly contradicts herself throughout her presentation, failing to realise that the stories she shared of her own patients disproved her vacuous inspirational memes.

Our biology affects each and every one of us. Our mind is a function of our brain. Our mind is to our brain as our breath is to our lungs. Put simply, without our brain, we would have no thoughts. If the structure and function of specific networks in our brains are altered, this changes our thinking. This is confirmed in everyday life – when someone suffers a brain injury or a stroke and they sustain damage to their brain, they suddenly lose the function of some, or all of their mind or body. Trans-cranial Magnetic Stimulation, Trans-cranial Direct Current Stimulation, metabolic states, prescription medications, illicit drugs, or everyday drugs like caffeine or alcohol have all been proven to change the subjects mental state through changes to the function of their brain. Any suggestion that our brain does not control our mind is simply ludicrous.

Clearly then our biology does control our psychology. Real cognitive neuroscientists have shown that our stream of thought is simply a tiny fraction of our overall neural activity, a conscious glimpse of the brains overall function [9-11], like the tachometer is for the engine in your car. Thus, our mind does not change our brain at all. Rather, it is our brain’s directed activity causing the growth of new synaptic branches to support it, something which the brain does without the function of conscious thought from the time when we were embryos.

Dr Leaf actually confirms this fact through her stories of her brain injured patients. After all, if “the mind is separate from the brain but influencing the brain”, then how could those victims of acquired brain injury lose cognitive function after their injury? If it were true that “each and every one of us is not a victim of our biology. We are a victor over and above our biology. We control our brain, our brain does not control us”, then how could those people with damage to their brains from strokes suddenly lose function?

The fact that Dr Leaf’s patients lost their mental or cognitive function because of damage to their brains directly contradicts her insistence that our brain and our mind are separate, and that our brain does not control our mind.


Considered altogether, Dr Leaf’s teaching boils down to a few fundamentals;
* Thought is the main driving force that controls every other aspect of our lives (and our physical world).
* We have full control over our thoughts.
* Thought causes stress.
* Stress is directly responsible for nearly all serious physical and mental illness.
* Therefore thought causes the vast majority of human disease, making thoughts toxic, and
* If toxic thoughts cause disease, “detoxing” thoughts will cure or prevent disease.

On first inspection, each individual postulate doesn’t seem so bad. However, when fully considered and taken to their natural conclusions, they veer into conjecture and pseudoscience, as evidenced by Dr Leaf’s published works and public appearances.

For example, Dr Leaf states in her books:

“Thoughts influence every decision, word, action and physical reaction we make.” [12: p13]
“Our mind is designed to control the body, of which the brain is a part, not the other way around. Matter does not control us; we control matter through our thinking and choosing.” [13: p33]
“DNA actually changes shape according to our thoughts.” [13: p35]

On Facebook and in interviews, this translates to:

“Our genetic makeup fluctuates by the minute based on what we are thinking and choosing.” 27/9/2014
“The toxic thoughts in our minds become physical baggage in our brain, which literally cause brain damage.” 5/12/2014, 27/10/2014 and 7/10/2014
“Your mind will adjust your body’s biology and behaviour to fit with your beliefs.” 21/6/2014

“SID ROTH: But when you told me that we could change our genes I wish every doctor in the world would understand this cutting edge research because, you know, you go to a doctor and say your cholesterol was high, and they say, well, exercise, change your diet, but it could be your genes and there’s nothing you can do, so take this medicine that will have a zillion side effects. But you say, according to the latest brain research, if you follow what Jesus said you can change your genes. That’s just so amazing.
DR. LEAF: I know. It is phenomenal. If you think of it, it’s logical too, Sid …” Full transcript:

Dr Leaf draws her erroneous conclusions from the poor interpretation of poor evidence. For example, one of Dr Leaf’s favourite factoids is her statement that “Research shows that 75 to 98 percent of mental, physical and behavioral illness comes from one’s thought life.” [13: p33] Dr Leaf’s sources for this statement include, among others, an article that not only doesn’t mention the figure she attributes to it, but also directly contradicts her fundamental premise [14], and the misleading paraphrasing of an already dubious quote from a pseudoscientific author [15].

Dr Leaf also has a number of pet theories which betray her preference for pseudoscience, the main one being her assertion that the heart is actually a mini-brain that has dedicated cognitive functions. For example, in her books, she says,

“Your heart is in constant communication with your brain and the rest of your body, checking the accuracy and integrity of your thought life.   As you are about to make a decision, your heart pops in a quiet word of advice, well worth listening to, because when you listen to your heart, it secretes the ANF hormone that gives you a feeling of peace.” [12: p62, 13: p127]

Dr Leaf directly quotes the work of an organisation called HeartMath for her evidence that the heart acts as a mini-brain. Dr Leaf, via Heartmath, states that:
> The heart has a network of 40,000 neurons within it, called sensory neurites, which detect circulating hormones, neurochemicals, and sense heart rate and blood pressure,
> The heart secretes “neurotransmitters” and other hormones, which have an effect on the brain, such as atrial natriuretic factor, and oxytocin,
> The heart communicates with the brain and the rest of the body through neurological, biophysical, biochemical and “energetic” (ie: electromagnetic) means [16, 17].

HeartMath clarifies, “The heart’s brain is an intricate network of several types of neurons, neurotransmitters, proteins and support cells like those found in the brain proper. Its elaborate circuitry enables it to act independently of the cranial brain – to learn, remember, and even feel and sense.” [16]

So the “evidence” looks plausible on the surface, but absurd when considered in a broader biological context. For example, my heart may have 40,000 neurons, many of which are sensitive to circulating hormones, neurochemicals and which sense and feel, but then again, so does my rectum. Does my rectum have a mini-brain as well? Clearly not. The only brain you have is the one in your cranium. We do not think with our heart, our rectum, or any other body part.

A more in-depth rebuttal of Dr Leaf’s scientific claims can be found in my book: “Hold That Thought – Reappraising the work of Dr Caroline Leaf”, via Smashwords ( or iTunes (


The opening question from Dr Leaf’s presentation at the 2015 TEDx Oaks Christian School was, “Can the mind change the brain?”

Clearly the answer is: “No, it can not.”

Others are welcome to disagree, but in my humble opinion, I suggest that Dr Leaf is a pseudoscientist, and that her appearance on the TEDx stage is not based on scientific acumen, but on popularity and reputation, which in turn, is based on slick self-promotion and an availability cascade (a self-reinforcing process by which an idea gains plausibility through repetition).

Dr Leaf’s ideas may have popular approval, but TEDx is a vehicle for ideas worth spreading, not ideas that are popular. According to its guidelines, TEDx requests that pseudoscience be avoided, specifically stating, “TED and TEDx are platforms for showcasing and explaining genuine advances in science … Speakers should avoid the misuse of scientific language to make unsubstantiated claims.” (

Dr Leaf’s claims, that her research has significantly changed the lives of the students who were blessed to receive it, is simply not born out by any of her own published data – from her original case study through to her MMA project and her Switch On Your Brain program. Whatever the underlying reason … whether its hubris, naivety, or denial that’s driving her continued promotion of her own programs … her claims are baseless, and therefore an argument can be made that she breached the TEDx guidelines in presenting them, and indeed, she should never have been invited to deliver them from a TEDx stage in the first place.

The theme for the 2015 TEDx Oaks Christian School event was “Ridiculous”. I would argue that it was ridiculous that Dr Leaf promoted her research as life changing when in reality, it’s not much better than a placebo. It was ridiculous that Dr Leaf would share stories of the changes to the cognitive functioning of her patients from their brain damage and then claim that the brain does not influence the mind. It seems that Dr Leaf’s presentation certainly fitted their theme, although probably not in the way they intended. Lets hope for their sake that their “ridiculous” decision doesn’t effect their ability to host future TEDx presentations.

Of course, that’s just my opinion. What do you think, TEDx universe?


  1. Leaf, C.M., et al., Mind-Mapping approach (MMA): a culture and language” free” technique. The South African journal of communication disorders. Die Suid-Afrikaanse tydskrif vir Kommunikasieafwykings, 1993. 40: 35
  2. Leaf, C.M., The Mind Mapping Approach: a model and framework for geodesic learning, in Department of Communication Pathology, Faculty of Arts1997, University of Pretoria: Pretoria. p. 266.
  3. Leaf, C.M., et al., The development of a model for geodesic learning: the geodesic information processing model. The South African journal of communication disorders. Die Suid-Afrikaanse tydskrif vir Kommunikasieafwykings, 1997. 44: 53
  4. Eppler, M.J., A comparison between concept maps, mind maps, conceptual diagrams, and visual metaphors as complementary tools for knowledge construction and sharing. Information Visualization, 2006. 5(3): 202-10
  5. Farrand, P., et al., The efficacy of the `mind map’ study technique. Medical Education, 2002. 36(5): 426-31 doi: 10.1046/j.1365-2923.2002.01205.x
  6. Wickramasinghe, A., et al., Effectiveness of mind maps as a learning tool for medical students. South East Asian Journal of Medical Education, 2007. 1(1): 30-2
  7. D’Antoni, A.V., et al., Does the mind map learning strategy facilitate information retrieval and critical thinking in medical students? BMC Med Educ, 2010. 10: 61 doi: 10.1186/1472-6920-10-61
  8. Merchie, E. and Van Keer, H., Spontaneous Mind Map use and learning from texts: The role of instruction and student characteristics. Procedia – Social and Behavioral Sciences, 2012. 69: 1387-94
  9. Baars, B.J., Global workspace theory of consciousness: toward a cognitive neuroscience of human experience. Progress in brain research, 2005. 150: 45-53
  10. Baars, B.J. and Franklin, S., An architectural model of conscious and unconscious brain functions: Global Workspace Theory and IDA. Neural Netw, 2007. 20(9): 955-61 doi: 10.1016/j.neunet.2007.09.013
  11. Franklin, S., et al., Conceptual Commitments of the LIDA Model of Cognition. Journal of Artificial General Intelligence, 2013. 4(2): 1-22
  12. Leaf, C., Who Switched Off My Brain? Controlling toxic thoughts and emotions. 2nd ed. 2009, Inprov, Ltd, Southlake, TX, USA:
  13. Leaf, C.M., Switch On Your Brain : The Key to Peak Happiness, Thinking, and Health. 2013, Baker Books, Grand Rapids, Michigan:
  14. Cohen, S., et al., Psychological stress and disease. JAMA: the journal of the American Medical Association, 2007. 298(14): 1685-7
  15. Lipton, B.H., The biology of belief: Unleashing the power of consciousness, matter and miracles. 2008, Hay House, Inc:
  16. Rosch, P. Emotional balance and health. Science of The Heart: Exploring the Role of the Heart in Human Performance – An Overview of Research Conducted by the Institute of HeartMath 2013 [cited 2013, 16/7/2013]; Available from:
  17. Rosch, P. Head-Heart Interactions. Science of The Heart: Exploring the Role of the Heart in Human Performance – An Overview of Research Conducted by the Institute of HeartMath 2013 [cited 2013, October 20]; Available from:

Dr Caroline Leaf and the cart-before-the-horse conundrum

Screen Shot 2014-10-05 at 6.54.03 pm

A chaotic mind filled with thoughts of anxiety, worry, etc. sends out the wrong signal right down to the level of our DNA

So says Dr Caroline Leaf, communication pathologist and self-titled cognitive neuroscientist.

Her Facebook factoids have varied in their quality lately, ranging from the almost reasonable, down to the outright ridiculous. Today’s contribution rates an 8.5 out of 10 on the pseudoscience scale.

The reason why it rates so high is for the same reason why many of her factoids, and indeed nearly all her teaching, rates the same: Dr Leaf has the relationship between the brain and the mind back to front.  Dr Leaf squarely puts the proverbial cart before the horse.

One would think if you were going to claim to be a cognitive neuroscientist, you would at least get the basic facts right. But Dr Leaf’s teaching, from her first book through to her last, is based on this idea that it’s the mind that is in control of the brain, hence why she thinks that thoughts can be so toxic.

Dr Leaf’s entire teaching heavily rests on her fallacious assumption that the mind is in control of the brain. Thoughts are only important if the mind controls the brain. Toxic thoughts can only affect our health if the mind controls the body. Controlling toxic thoughts is only worthwhile if our mind can influence our brain and body in positive or negative ways.

The problem for Dr Leaf is that there is no credible scientific evidence that the mind controls the brain. The only evidence she does tend to proffer is based on the work of other pseudoscientists, or she misinterprets or misquotes real scientific data to fit her erroneous working theory. For example, Dr Leaf refers to a paper titled, “Local and nonlocal effects of coherent heart frequencies on conformational changes of DNA” [1]. She says that this paper is, “An ingenuous experiment set up by the HeartMath Foundation (which) determined that genuine positive emotion, as reflected by a measure called ‘heart rate variability’, directed with intentionality towards someone actually changed the way the double helix DNA strand coils and uncoils. And this goes for both positive and negative emotions and intentions.” [2: p111] Actually, the experiment was based on faulty assumptions, and so full of flaws in their methodology and analysis, that it could show nothing at all [3]. All it could prove was that Dr Leaf was so desperate to grasp hold of anything that seemed to support her theory that she was willing to use a twenty-year-old study from a group of pseudoscientists that also believe in occult practices like ESP and telekinesis (

The concept that we have a soul that’s separate to, and controls our brain, is called dualism. Modern science gave up on dualism a long time ago. While psychological sciences have been slower to give up on the idea of our thoughts as influential, no credible scientist still holds on to the idea that we have an ethereal force that controls our biology. Dualism is untenable both scientifically and philosophically [4].

The reality is the exact opposite to what Dr Leaf teaches. Our brain is responsible for all of the functions that are traditionally associated with the mind/soul/spirit. For more in depth information, please see my essay: Dr Caroline Leaf, Dualism, and the Triune Being Hypothesis. Therefore, a “chaotic mind filled with thoughts of anxiety, worry, etc” doesn’t send signals down to our DNA. It’s our DNA and the many steps in it’s expression, and the interaction of our biology and our environment, that then causes our minds to be worried, anxious, chaotic etc.

Dr Leaf is welcome to hold any view she likes, but she cannot claim to be a cognitive neuroscientist while holding a view that is directly contradicted by actual cognitive neuroscience. Nor should she be welcome to speak as an expert when she clearly is not one.

For the sake of her audiences and the Christian church as a whole, Dr Leaf needs to revise her teaching and bring it into line with the facts established by real cognitive neuroscientists.


  1. Rein, G. and McCraty, R. Local and nonlocal effects of coherent heart frequencies on conformational changes of DNA. in Proc. Joint USPA/IAPR Psychotronics Conf., Milwaukee, WI. 1993.
  2. Leaf, C.M., Switch On Your Brain : The Key to Peak Happiness, Thinking, and Health. 2013, Baker Books, Grand Rapids, Michigan:
  3. Pitt, C.E., Hold That Thought: Reappraising the work of Dr Caroline Leaf, 2014 Pitt Medical Trust, Brisbane, Australia, URL
  4. Bunge, M., The Mind-Body Problem, in Matter and Mind. 2010, Springer Netherlands. p. 143-57.

Dr Caroline Leaf and Picking Cherries

Screen Shot 2014-09-20 at 11.58.36 am

When it comes to fruit, I’m a bit picky. Cherries are one of my least favourite. It makes things difficult at times. I’m no good with Black Forest cake or with traditional Christmas goodies like Christmas pudding or rumballs. I guess that’s a good thing, one less thing to be tempted by.

Some fruit can be picked a little unripe, because it will still ripen after it’s picked. Cherries are a bit more delicate. Apparently when it comes to picking cherries, the key is to pick only the ripest fruit and leave the rest on the tree.

In science, “cherry picking” is a colloquial expression for the practice of selectively picking or presenting only the information that agrees with your personal theory, ignoring the rest. Richard Somerville put it well: “Choosing to make selective choices among competing evidence, so as to emphasize those results that support a given position, while ignoring or dismissing any findings that do not support it, is a practice known as ‘cherry picking’ and is a hallmark of poor science or pseudo-science.” (Testimony before the US House of Representatives Committee on Energy and Commerce Subcommittee on Energy and Power, March 8, 2011).

You can see cherry picking everywhere if you know what to look for. It’s usually done by advertising and PR firms to make a product sound all sciencey or mediciney, something like, “Research shows that …”. Then deep in the fine print is a reference to a single scientific paper. When you actually look at the article in question, the “research” is weak or horribly biased.

Cherry picking is also common amongst organisations with a barrow to push, or websites like Natural Wellness Care (, which push a bunch of statistics to magnify a problem so they can sell or promote their “solution”.

Dr Caroline Leaf is a communication pathologist and a self-titled cognitive neuroscientist. Cherry picking is one of her favourite tricks. Her teaching from the pulpit is littered with the phrase, “Research says …”, without ever mentioning where the research came from. You just have to take her word for it.

Dr Leaf cherry picks extensively through her published work. There are too many examples to list them all, but her use of the quantum physics term, “quantum Zeno effect” is a prime example [1: p108, 2: ch13].

Another great example of cherry picking is Dr Leaf’s theory of the “Heart as a mini-brain” [2: ch11, 3: p40]. Dr Leaf exclusively relies on the information published by a group called HeartMath (, who themselves cherry pick extensively. HeartMath list reams of citations as evidence that the heart is a little brain, but even a basic understanding of routine clinical tests like an ECG shows that their ground breaking discoveries are little more than pseudoscience [see also Ref 2: ch11].

Dr Leaf then selectively uses certain studies from HeartMath to back up various claims she makes. A case in point is her claim that, “An ingenuous experiment set up by the HeartMath Foundation determined that genuine positive emotion, as reflected by a measure called ‘heart rate variability’, directed with intentionality towards someone actually changed the way the double helix DNA strand coils and uncoils. And this goes for both positive and negative emotions and intentions.” [1: p111]

This is cherry picking in its purest form. Despite the study being over 20 years old, and so badly designed that even alternative scientific journals wouldn’t publish it, Dr Leaf claimed it as proof that emotions and intentions can alter DNA [Chapter 13 of my book, Ref 2 outlines why the study is so poor].

In her social media feed today, Dr Leaf quoted Peace Pilgrim, a silver haired mystic who walked across America for 28 years, owning nothing but the clothes on her back, all in the name of peace. The quote Dr Leaf republished was, “If you realized how powerful your thoughts are, you would never think a negative thought.” This was taken from a radio talk that Peace Pilgrim gave in 1964 ( Peace Pilgrim’s quote is interesting, even inspirational, but not scientific. Inspiring quotes from half a century ago are fine, but only if you’re a motivational speaker or a B-grade life coach.

Dr Leaf says she’s a cognitive neuroscientist. Real cognitive neuroscientists don’t cherry pick whichever quotes or studies fit with their prevailing theory. They look for the truth by synthesising all the evidence into an accurate theory.

Dr Leaf may be trying to inspire people, but if she claims to be a scientist of any form, she has to adhere to a higher standard. She has to make sure that the words she uses are not just inspiring, but accurate as well, because facts and fruit are not the same. If you want a good Black Forest cake, then cherry pick all you want, but if you want the truth, consider all the facts first.

Like to read more about Dr Leaf’s teaching and how it compares to current science? Download the free eBook HOLD THAT THOUGHT, Reappraising The Work Of Dr Caroline Leaf


  1. Leaf, C.M., Switch On Your Brain : The Key to Peak Happiness, Thinking, and Health. 2013, Baker Books, Grand Rapids, Michigan:
  2. Pitt, C.E., Hold That Thought: Reappraising the work of Dr Caroline Leaf, 2014 Pitt Medical Trust, Brisbane, Australia, URL
  3. Leaf, C., Who Switched Off My Brain? Controlling toxic thoughts and emotions. 2nd ed. 2009, Inprov, Ltd, Southlake, TX, USA:

Dr Caroline Leaf – Contradicted by the latest research

This is my most popular post by far.  I truly appreciate the support and interest in this post, but I’ve discovered and documented a lot more about Dr Leaf’s ministry in the last two years.  I welcome you to read this post, but if you’d like a more current review of the ministry of Dr Caroline Leaf, a new and improved version is here:
Dr Caroline Leaf – Still Contradicted by the Latest Evidence, Scripture & Herself

* * * * *

Mr Mac Leaf, the husband of Dr Caroline Leaf, kindly took the time to respond to my series of posts on the teachings of Dr Leaf at Kings Christian Centre, on the Gold Coast, Australia, earlier this month. As I had intended, and as Mr Leaf requested, I published his  reply, complete and unabridged (here).

This blog is my reply.  It is heavily researched and thoroughly referenced.  I think it’s fair to say that while Dr Leaf draws her conclusions from some scientific documents, there is more than enough research that contradicts her statements and opinions.  I have only listed a small fraction, and only on some of the points she raised.

In fairness, the fields of neurology and neuroscience are vast and rapidly expanding, and it is impossible for one person to cover all of the literature on every subject.  This applies to myself and Dr Leaf.  However, I believe that the information I have read, and referenced from the latest peer-reviewed scholarly works, do not support Dr Leaf’s fundamental premises.  If I am correct, then the strength and validity of Dr Leaf’s published works should be called into question.

As before, I welcome any reply or rebuttal that Dr Leaf wishes to make, which I will publish in full if she requests.  In the interests of healthy public debate, and encouraging people to make their own informed decisions on the teachings of Dr Leaf, any comments regarding the response of Mr Leaf, Dr Leaf or myself, are welcome provided they are constructive.

This is a bit of a lengthy read, but I hope it is worthwhile.

Dear Mr Leaf,

Thank you very much for taking the time out to reply to some of the points raised in my blog.  I am more than happy to publish your response, and to publish any response you wish to make public.


I published my blog posts to open up discussion on the statements made by Dr Leaf at the two meetings that I attended at Kings Christian Centre on the Gold Coast.  As you rightly point out, people should be able to make informed decisions.  A robust discussion provides the information required for people to make an informed choice.  Any contributions to this discussion from either yourself or Dr Leaf would be most welcome.

I apologise if you interpreted my blogs as judgemental, or if you believe there are any misunderstandings.  You may or may not have read my final two paragraphs from the third post, in which I acknowledged that I may have misunderstood where she was coming from, but that I would welcome her response.  If there were any misunderstandings, it is likely because Dr Leaf did not make any attempt to reference any of the statements she made on the day.  You may argue that she was speaking to a lay audience, and referencing is therefore not necessary.  However, I have been to many workshops for the lay public by university professors, who have extensively referenced their information during their presentations.  A lay audience does not preclude providing references.  Rather, it augments the speakers authority and demonstrates the depth of their knowledge on the subject at hand.


It’s interesting that you feel the need to resort to defence by association, and Ad Hominem dismissal as your primary counter to the points I raised.

Can you clarify how attending the same university as Dr Christaan Barnard, or a Nobel laureate, endorses her arguments or precludes her from criticism?  I attended the University of Queensland where Professor Ian Frazer was based.  He developed the Human Papilloma Virus vaccine and was the 2006 Australian of the Year.  Does that association enhance my argument?

Can you also clarify why a reference from a colleague was preferred to letting Dr Leaf’s statements and conclusions speak for themselves?  Dr Amua-Quarshie’s CV is certainly very impressive, no doubt about that, although he doesn’t list the papers he’s published.  (I’m assuming that to hold the title of Adjunct Professor, he’s published peer-reviewed articles.  Is he willing to list them, for the record?)

Whatever his credentials, his endorsement means very little, since both Dr Leaf and Dr Amua-Quarshie would know from their experience in research that expert opinion is one of the lowest forms of evidence, second worst only to testimonials [1].  Further, both he and Dr Leaf are obviously close friends which introduces possible bias.  His endorsement is noteworthy, but it can not validate every statement made by Dr Leaf.  Her statements should stand up on their own through the rigors of critical analysis.

On the subject of evidence, disparaging your critics is not a substitute for answering their criticism.  Your statement, “By your comments it is obvious that you have not kept up to date with the latest Scientific research” is an assumption that is somewhat arrogant, and ironic since Dr Leaf is content to use superseded references dating back to 1979 to justify her current hypotheses.


In the blog to which you referred, Dr Leaf makes a number of statements that are intended to support her case.  These include the following.

“A study by the American Medical Association found that stress is a factor in 75% of all illnesses and diseases that people suffer from today.”  She fails to reference this study.

“The association between stress and disease is a colossal 85% (Dr Brian Luke Seaward).”   But again, she fails to reference the quote.

“The International Agency for Research on Cancer and the World Health Organization has concluded that 80% of cancers are due to lifestyles and are not genetic, and they say this is a conservative number (Cancer statistics and views of causes Science News Vol.115, No 2 (Jan.13 1979), p.23).”  It’s good that she provides a reference to her statement.  However, referencing a journal on genetics from 1979 is the equivalent of attempting to use the land-speed record from 1979 to justify your current preference of car.  The technology has advanced significantly, and genetic discoveries are lightyears ahead of where they were more than three decades ago.

“According to Dr Bruce Lipton (The Biology of Belief, 2008), gene disorders like Huntington’s chorea, beta thalassemia, cystic fibrosis, to name just a few, affect less than 2% of the population. This means the vast majority of the worlds population come into this world with genes that should enable the to live a happy and healthy life. He says a staggering 98% of diseases are lifestyle choices and therefore, thinking.”  Even if it’s true that Huntingtons, CF etc account for 2% of all illnesses, they account for only a tiny fraction of genetic disease.  And concluding that the remaining 98% must therefore be lifestyle related is overly simplistic.  It ignores the genetic influence on all other diseases, other congenital, and environmental causes of disease.  I will fully outline this point soon.

Similarly, “According to W.C Willett (balancing lifestyle and genomics research for disease prevention Science (296) p 695-698, 2002) only 5% of cancer and cardiovascular patients can attribute their disease to hereditary factors.”  Science is clear that genes play a significant role in the development of cardiovascular disease and most cancers, certainly greater than 5%.  Again, I will discuss this further soon.

“According to the American Institute of health, it has been estimated that 75 – 90% of all visits to primary care physicians are for stress related problems ( Some of the latest stress statistics causing illness as a result of toxic thinking can be found at:”  These websites not peer-reviewed, and both suffer from a blatant pro-stress bias.

You’ll also have to forgive my confusion, but Dr Leaf also wrote, “Dr H.F. Nijhout (Metaphors and the Role of Genes and Development, 1990) genes control biology and not the other way around.”  So is she saying that genes DO control development?


Influence Of Thought On Health

Dr Leaf has categorically stated that “75 to 98% of all illnesses are the result of our thought life” on a number of occasions.  She repeated the same statement in her most recent book so it is something she is confident in.  However, in order to be true, this fact must be consistent across the whole of humanity.

And yet, in a recent peer-reviewed publication, Mara et al state, “At any given time close to half of the urban populations of Africa, Asia, and Latin America have a disease associated with poor sanitation, hygiene, and water.” [2]  Bartram and Cairncross write that “While rarely discussed alongside the ‘big three’ attention-seekers of the international public health community—HIV/AIDS, tuberculosis, and malaria—one disease alone kills more young children each year than all three combined. It is diarrhoea, and the key to its control is hygiene, sanitation, and water.” [3]  Hunter et al state that, “diarrhoeal disease is the second most common contributor to the disease burden in developing countries (as measured by disability-adjusted life years [DALYs]), and poor-quality drinking water is an important risk factor for diarrhoea.” [4]

Toilets and clean running water have nothing to do with stress or thought.  We live in a society that essentially prevents more than half of our illnesses because of internal plumbing, with additional benefits from vaccination and population screening.  If thoughts have any effect on our health, they are artificially magnified by our clean water and sewerage systems.  Remove those factors and any effects of thought on our health disappear from significance.  Dr Leaf’s assertion that 75 to 98% of human illness is thought-related is a clear exaggeration.

Let me be clear – I understand the significance of stress on health and the economy, but it is not the cause of 75-98% of all illnesses.  I’m not sure if there is a similar study in the US, but the latest Australian data suggests that all psychological illness only counts for 8% of visits to Australian primary care physicians [5].

In terms of cancer, I don’t have time to exhaustively list every cancer but of the top four listed in the review “Cancer Statistics 2013” [6] , here are the articles that list the gene x environment interactions:

  1. PROSTATE – There are only two risk factors for prostate cancer, familial aggregation and ethnic origin. No dietary or environmental cause has yet been identified [7].  It is most likely caused by multiple genes at various loci [8].
  2. BREAST – Genes make up 25% of the risk factors for breast cancer, and significantly interacted with parity (number of children born) [9].
  3. LUNG/BRONCHUS – Lung cancer is almost exclusively linked to smoking, but nicotine addiction has a strong hereditary link (50-75% genetic susceptibility) [10].
  4. COLORECTUM – Approximately one third of colorectal cancer is genetically linked [11].

So the most common cancer is not linked to any environmental factors at all, and the others have genetic influences of 25% to more than 50%.  This is far from being 2% or 5% as Dr Leaf’s sources state.

Also in terms of heart disease, the INTERHEART trial [12] lists the following as significant risk factors, and I have listed the available gene x environment interaction studies that have been done on these too:

  1. HIGH CHOLESTEROL – Genetic susceptibility accounts for 40-60% of the risk for high cholesterol [13].
  2. DIABETES – Genetic factors account for 88% of the risk for type 1 diabetes [14].  There is a strong genetic component of the risk of type 2 diabetes with 62-70% being attributable to genetics [15, 16].
  3. SMOKING – nicotine addiction has a strong hereditary link (50-75% genetic susceptibility) [10].
  4. HYPERTENSION – While part of a much greater mix of variables, genetics are still thought to contribute between 30% and 50% to the risk of developing high blood pressure [17].

So again, while genes are a part of a complex system, it is clear from the most recent evidence that genetics account for about 50% of the risk for cardiovascular disease, which again is a marked difference between the figures that Dr Leaf is using to base her assertions on.

Atrial Natriuretic Peptide

I am aware of research that’s studied the anxiolytic properties of Atrial Natriuretic Peptide.  For example, Wiedemann et al [18] did a trial using ANP to truncate panic attacks.  However, these experiments were done on only nine subjects, and the panic attacks were induced by cholecystokinin.  As such, the numbers are too small to have any real meaning.  And the settling is completely artificial.  Just as CCK excretion does not cause us all to have panic attacks every time we eat, ANP does not provide anxiolysis in normal day to day situations.  Besides, if ANP were really effective at reducing anxiety, then why do people suffering from congestive cardiac failure, who have supraphysiological levels of circulating ANP [19] , also suffer from a higher rate of anxiety and panic disorders than the general population? [20]

The Heart As A Mini-Brain

As for Heartmath, they advance the notion of the heart being a mini-brain to give themselves credibility.  It’s really no different to an article that I read the other day from a group of gut researchers [21] – “‘The gut is really your second brain,’ Greenblatt said. ‘There are more neurons in the GI tract than anywhere else except the brain.’”  The heart as a mini-brain and the gut as a mini-brain are both figurative expressions.  Neither are meant to be taken literally.  I welcome Dr Leaf to tender any further evidence in support of her claim.

Hard-Wired For Optimism

As for being wired for optimism, the brain is likely pre-wired with a template for all actions and emotions, which is the theory of protoconsciousness [22].  Indeed, neonatal reflexes often reflect common motor patterns.  If this is true, then the brain is pre-wired for both optimism and love, but also fear.  This explains the broad role of the amygdala in emotional learning [23] including fear learning.  It also means that a neonate needs to develop both love and fear.

A recent paper showed that the corticosterone response required to learn fear is suppressed in the neonate to facilitate attachment, but with enough stress, the corticosterone levels build to the point where amygdala fear learning can commence [24].  The fear circuits are already present, only their development is suppressed.  Analysis of the cohort of children in the Bucharest Early Intervention Project showed that negative affect was the same for both groups.  However positive affect and emotional reactivity was significantly reduced in the institutionalised children [25].  If the brain is truly wired for optimism and only fear is learned, then positive emotional reactivity should be the same in both groups and the negative affect should be enhanced in the institutionalised cohort.  That the result is reversed confirms that neonates and infants require adequate stimulation of both fear and love pathways to grow into an emotionally robust child, because the brain is pre-wired for both but requires further stimulation for adequate development.

The Mind-Brain Link

If the mind controls the brain and not the other way around as Dr Leaf suggests, why do anti-depressant medications correct depression or anxiety disorders?  There is high-level evidence to show this to be true [26-28].  The same can be said for recent research to show that medications which enhance NDMA receptors have been shown to improve the extinction of fear in anxiety disorders such as panic disorder, OCD, Social Anxiety Disorder, and PTSD [29].

If the mind controls the brain and not the other way around as Dr Leaf suggests, why do some people with acquired brain injuries or brain tumours develop acute personality changes or thought disorders?  Dr Leaf has done PhD research on patients with closed head injuries and treated them in clinical settings according to her CV.  She must be familiar with this effect.

One can only conclude that there is a bi-directional effect between the brain and the stream of thought, which is at odds with Dr Leaf’s statement that the mind controls the brain and not the other way around.


One further thing.  Can you clarify which of Dr Leaf’s peer-reviewed articles have definitively shown the academic improvement in the cohort of 100,000 students, as you and your referee have stated?  And can you provide a list of articles which have cited Dr Leaf’s Geodesic Information Processing Model?  Google Scholar did not display any articles that had cited it, which must be an error on Google’s part.  If her theory is widely used as you say, it must have been extensively cited.

I understand that you are both busy, but I believe that I have documented a number of observations, backed by recent peer-reviewed scientific literature, which directly contradict Dr Leaf’s teaching.  I have not had a chance to touch on many, many other points of disagreement.

For the benefit of Dr Leaf’s followers, and for the scientific and Christian community at large, I would appreciate your response.

I would be grateful if you could respond to the points raised and the literature which supports it, rather than an Ad Hominem dismissal or further defense by association.

Dr C. Edward Pitt


1. Fowler, G., Evidence-based practice: Tools and techniques. Systems, settings, people: Workforce development challenges for the alcohol and other drugs field, 2001: 93-107.

2. Mara, D., et al., Sanitation and health. PLoS Med, 2010. 7(11): e1000363.

3. Bartram, J. and Cairncross, S., Hygiene, sanitation, and water: forgotten foundations of health. PLoS Med, 2010. 7(11): e1000367.

4. Hunter, P.R., et al., Water supply and health. PLoS Med, 2010. 7(11): e1000361.

5. FMRC. Public BEACH data. 2010  16JUL13]; Available from: <;.

6. Siegel, R., et al., Cancer statistics, 2013. CA Cancer J Clin, 2013. 63(1): 11-30.

7. Cussenot, O. and Valeri, A., Heterogeneity in genetic susceptibility to prostate cancer. Eur J Intern Med, 2001. 12(1): 11-6.

8. Alberti, C., Hereditary/familial versus sporadic prostate cancer: few indisputable genetic differences and many similar clinicopathological features. Eur Rev Med Pharmacol Sci, 2010. 14(1): 31-41.

9. Nickels, S., et al., Evidence of gene-environment interactions between common breast cancer susceptibility loci and established environmental risk factors. PLoS Genet, 2013. 9(3): e1003284.

10. Berrettini, W.H. and Doyle, G.A., The CHRNA5-A3-B4 gene cluster in nicotine addiction. Mol Psychiatry, 2012. 17(9): 856-66.

11. Hutter, C.M., et al., Characterization of gene-environment interactions for colorectal cancer susceptibility loci. Cancer Res, 2012. 72(8): 2036-44.

12. Yusuf, S., et al., Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. Lancet, 2004. 364(9438): 937-52.

13. Asselbergs, F.W., et al., Large-scale gene-centric meta-analysis across 32 studies identifies multiple lipid loci. Am J Hum Genet, 2012. 91(5): 823-38.

14. Wu, Y.L., et al., Risk factors and primary prevention trials for type 1 diabetes. Int J Biol Sci, 2013. 9(7): 666-79.

15. Ali, O., Genetics of type 2 diabetes. World J Diabetes, 2013. 4(4): 114-23.

16. Murea, M., et al., Genetic and environmental factors associated with type 2 diabetes and diabetic vascular complications. Rev Diabet Stud, 2012. 9(1): 6-22.

17. Kunes, J. and Zicha, J., The interaction of genetic and environmental factors in the etiology of hypertension. Physiol Res, 2009. 58 Suppl 2: S33-41.

18. Wiedemann, K., et al., Anxiolyticlike effects of atrial natriuretic peptide on cholecystokinin tetrapeptide-induced panic attacks: preliminary findings. Arch Gen Psychiatry, 2001. 58(4): 371-7.

19. Ronco, C., Fluid overload : diagnosis and management. Contributions to nephrology,. 2010, Basel Switzerland ; New York: Karger. viii, 243 p.

20. Riegel, B., et al., State of the science: promoting self-care in persons with heart failure: a scientific statement from the American Heart Association. Circulation, 2009. 120(12): 1141-63.

21. Arnold, C. Gut feelings: the future of psychiatry may be inside your stomach. 2013  [cited 2013 Aug 22]; Available from:

22. Hobson, J.A., REM sleep and dreaming: towards a theory of protoconsciousness. Nat Rev Neurosci, 2009. 10(11): 803-13.

23. Dalgleish, T., The emotional brain. Nat Rev Neurosci, 2004. 5(7): 583-9.

24. Landers, M.S. and Sullivan, R.M., The development and neurobiology of infant attachment and fear. Dev Neurosci, 2012. 34(2-3): 101-14.

25. Bos, K., et al., Psychiatric outcomes in young children with a history of institutionalization. Harv Rev Psychiatry, 2011. 19(1): 15-24.

26. Arroll, B., et al., Antidepressants versus placebo for depression in primary care. Cochrane Database Syst Rev, 2009(3): CD007954.

27. Soomro, G.M., et al., Selective serotonin re-uptake inhibitors (SSRIs) versus placebo for obsessive compulsive disorder (OCD). Cochrane Database Syst Rev, 2008(1): CD001765.

28. Kapczinski, F., et al., Antidepressants for generalized anxiety disorder. Cochrane Database Syst Rev, 2003(2): CD003592.

29. Davis, M., NMDA receptors and fear extinction: implications for cognitive behavioral therapy. Dialogues Clin Neurosci, 2011. 13(4): 463-74.