The Astrological Association Journal of Research in Astrology

Review Understanding Astrology: A critical review of a thousand empirical studies 1900 - 2020

by Robert Currey

A revised and enlarged edition of Tests of Astrology 2016 By Geoffrey Dean, Arthur Mather, David Nias and Rudolf Smit Published 2022 by AinO Publications: Amsterdam. 952 pages Available in hard cover 60 Euros or online for free at

Understanding Astrology (UA) traces its origins back to the 1977 classic Recent Advances in Natal Astrology by two of the authors: Dr Geoffrey Dean and Arthur Mather. However, UA diverges from its predecessor by fostering the conviction that astrology has no research-based empirical support. This newest collaborative effort, now in its third iteration, seeks to present its case to scientists, academics, students and astrologers.

The book is a result of a substantial investment of effort and resources, evolving from Astrology Under Scrutiny (2014) to Tests of Astrology (2016), and finally culminating in Understanding Astrology (2022). This last tome has expanded from 364 to a staggering 952 pages with text printed in regressively smaller font sizes. According to the authors, UA contains an astonishing 650,000 words, surpassing the word count of the Old Testament by about fifty thousand words. However, as an educated, contemporary audience will discover, the sheer volume of words can deter critical reading and, like biblical manuscript, can contain internal inconsistencies.

Aside from its bulk, Understanding Astrology (UA) raises questions regarding its intentions—is it a Bible for confirmed sceptics. A reader may justifiably wonder whether it is a modern-day Malleus Maleficarum (Latin: “Hammer of Witches” 1486), or an essential tool for critical thinkers. While certain sections of UA provide valuable clues for researchers seeking to improve their work, the book is marred by a disturbing number of misquotes, misreporting of metrics, omissions, and fallacious arguments. It is crucial that these damaging issues be called out and rectified.

ua review table1 v2

Table 1 Misleading arguments used by the authors of Understanding Astrology.

Table 1 lists some of the types of misinformation the authors level against the substantial evidence presented by ten respected researchers whose work they cite. One might question why such misleading arguments have entered into the discourse if astrology is based on delusion, as the authors contend. Frankly, a higher standard is to be expected from the authors, who have put so much time and effort into their work.

UA is too large and too detailed to review in one article and so I can offer only a brief overview here. Since UA turns out to be more about scientism than science, much of the content will have to be considered outside the scope of the printed copies of Correlation. For example, I have not addressed the quotations and the anecdotal evidence of former ‘believers’ who were spooked that the placebo effect applies as much to astrology as it does to medicine.

An ongoing discourse on these many issues is regularly updated on the Correlation website – Several researchers have responded to the UA criticism of their individual studies.

The overarching thesis of UA has not changed from its previous two versions:

The thesis and presumptions of Understanding Astrology:
The authors assert that astrology’s validity has been determined by a thousand tests and experiments– even though they do not provide any categorical list of the tests and can cite no single exemplary test that falsifies astrology. All the research evidence of Michel Gauquelin and his replications are glossed over to promote Dean’s far-fetched explanation of attribution bias that is unsupported by evidence and is unfalsifiable. All researchers who have contributed to the growing body of evidence supporting astrology are repudiated as unsuitable as they are astrologers, even those who do not identify themselves as such. The assumption is that all astrologers are biased and their results are suspect due to cherry picking and hidden psychological artefacts. All the researchers’ highly significant p-values are meaningless as the effect sizes are, allegedly, too small. Readers should place their trust in the sceptical authors as impartial defenders of rationality.

I reviewed Dean et al.’s first version, Astrology Under Scrutiny (2014) in Correlation (Currey, 2014). Since then, the authors have still not resolved many of their claims that I and others have contested. The main issues are summarized in the following list and are discussed in the corresponding sections that follow:

  1. Did astrology originate from observation or invention?
  2. Where are the hundreds and now thousands of empirical tests of astrology that confirm that there is nothing to astrology?
  3. The serious flaws in Dr Dean’s meta-analyses.
  4. Is Dean as the mastermind or merely a team player?
  5. The Gauquelin Evidence and Dean’s incredible Parental Tampering claim.
  6. A new addition is the reversal of the largest and most controversial study, the Carlson Test in favour of astrology.

Two Shifts
However, UA does appear to acknowledge two underlying shifts that recast the debate.

The first shift is that there is less focus on the statistical significance (p values) of astrological correlations, but more the measure of the effect (the Effect Size or ES).

“To test astrology we must ask the right questions. Not is astrology true? (What is truth?) Or does it work? (Can thousands of astrologers be wrong?) Instead we should ask about extent. To what extent does astrology predict behaviour? … In short, we should ask about effect size, the extent to which one thing is associated with another such as height and weight.” (UA, 2022 p.755)

This is a critical issue and it relates to the efforts that have been made to resolve the “replication crisis” that has affected all social sciences in recent years.

The second shift is more acceptance for astrology understood as divination. In 2014 Astrology Under Scrutiny’s heading “Retreat into divination” (2014 p.255) has become the more respectful “Astrology as Divination”.

“We have a case for astrology as divination in the special sense of giving us new viewpoints from which to explore personal issues, not in the popular sense of fortune-telling.” (2022 p.913)

Yet, all the UA authors may not agree with this as later on they claim that the practice of astrology is “unethical” if it cannot be proved under scientific test conditions (p.719).

Geoffrey Cornelius, author of the influential book The Moment of Astrology: Origins of Divination (1994), is not mentioned in their first version, Astrology Under Scrutiny. But now, eight years later, Cornelius is listed seventeen times in the index of UA. This revision is possibly down to the influence of co-author Arthur Mather and his apparent change of heart as per his comment:

“I now believe [the future of astrological practice] lies in the direction of recognising astrology as a divination.” (p.913)

This may be a significant step towards a “Non-Overlapping Magisteria” accord as coined by popular scientist Stephen Jay Gould for his model of the independence between science and religion as they explore separate domains that ask distinct questions. (Gould 2001 p.739). It gives astrology defenders some breathing space but not from militant atheists who concede no happy home between their ‘rational scepticism’ and the ‘irrational beliefs’ of others.

While I have deep respect for Cornelius’s thesis of an enchanted universe, my own empirical studies make me consider that astrology is more than the invocation of supernatural forces.

Arthur Mather (in personal correspondence 2023) has since clarified his position on divination. He does not attribute astrology’s successes “entirely to psychic effects”. In addition to divination, Mather is also open to unconscious factors within the realm of cognitive psychology and other paranormal possibilities besides psychism.

Origins of Astrology
1. The origins of Astrology: Observation or Invention?
Following on from their earlier versions of the book, the authors of UA persist in an argument that questions whether the cuneiform clay tablets discovered from ancient Mesopotamia are evidence of an early database of empirical information in the development of astrology, contrary to their view that astrology was simply made up from mythology and imagination.

“Notice also how Currey does not dispute our arguments by quoting experts on the history of astrology.” (UA p.718)

That is simply not correct. In my review of Astrology Under Scrutiny which they have referenced at several points in UA, I presented evidence from eminent historians:

“Assyriologists such as Abraham Sachs (1988) and Francesca Rochberg-Halton (1991), document over 600 years of Babylonian Astronomical Diaries. Star-gazing scholars recorded their nightly observations of celestial movements and terrestrial events on clay tablets in cuneiform script.” (Currey, 2014 p.61) 29.2 Review of Astrology Under Scrutiny

Dean and his authors would like to have us believe that astrology was invented. To admit evidence that astrology originated in part from empirical sources undermines their overarching hypothesis.

2. Thousand Empirical Studies
Validation by Democracy; the mythical ‘thousand’ studies
The main thesis of Understanding Astrology is based on the authors’ assertion that they have ‘trawled through a thousand empirical studies’ leading them to conclude that none of astrology’s claims are true beyond a level explained by self-attribution and other artifacts (UA p.918-919).

This assertion needs to be deconstructed.

While the authors claim they “trawled” through studies, it was more like dredging the seabed to try to salvage rusting wrecks. In the last century, apart from a few shining stars such as the Gauquelins, there were many faulty studies by enthusiastic amateurs unfamiliar with statistics or statisticians unfamiliar with astrology. They were many ups and downs. But without the setbacks of these pioneers, the Astrology Research Program would not be progressing so well today.

The UA authors never list their vaguely claimed ‘thousand studies’. The best lists I can find are on pages 863-4. Of the eighty-seven tests listed seventy-seven are from the last century. The most recent test was published fifteen years ago. Many were from an era when charts were calculated by hand. There were no relational databases, no astrological software and no statistical tools such as Minitab or Wolfram Alpha or even Excel.

Now, to delve deeper. The tests fall into roughly seven categories:

  1. Tests that are clearly flawed through lack of controls or artefacts and often both.
  2. Straw man tests that attempt to disprove a claim that Western astrologers do not make. For example, asking Vedic astrologers to identify the birth charts of children with intellectual disability in a blind test (Narlikar 2009).
  3. Tests that lack statistical power due to the sample size being too small for the effect size.
  4. Unscientific or anecdotal tests such as magician James Randi (1983) testing the proficiency of one astrologer.
  5. Tests that were never peer reviewed or even published.
  6. “No win” Sun Sign tests where significant and consistent results are dismissed as false self-attribution or due to artefacts or a lack of precision (due to no time of birth).
  7. Tests that provide evidence supporting astrology though the authors hide or ignore or contest this.

The Gish Gallop – drowning opponents in claims, cases and arguments
As for the daunting task of assessing and refuting hundreds of tests, I have, for many years, publicly invited sceptics, including Dr Dean (by personal correspondence) to cite their best single test that is consistent with their negative claims about astrology (UA p.716). Having inflated their defective tests from hundreds to a thousand, I am asking for just 1% — that is their ten most convincing tests refuting astrology.

The intention of this challenge is to get astrology critics to work out which tests are the best to hang their flag on. This requires critical thinking which is often lacking on both sides of the debate. Researcher Kenneth McRitchie (2016 p. 164) has supported the benefits of the “best examples” approach in his criticism of Dean, “As a whole, astrological research has very few examples of excellence but they do exist and they can serve as models to improve the research methodology.” Plus, critics and observers can discover the strengths and weaknesses for themselves and discover that the largest and most robust tests now support astrology.

Critics often respond to my challenge with an inundation of flawed or irrelevant tests. Their aim is to overwhelm their opponent with sheer quantity rather than considering the quality of the evidence. This is precisely the approach taken by the authors of UA. Their tactics follow what is known in sceptical circles as the Gish Gallop. This technique derives from Duane Gish, a fervent advocate for creationism who bombarded his opponents with an excessive number of arguments, misrepresentations and half-truths.

In internet forums, amateur sceptics frequently cite the Carlson Test (1985), unaware that the experiment has been shown to support astrology (Ertel, 2009) Or, they cite exercises that do not address astrology such as the Randi Million Dollar Paranormal challenge. (see

But his [Currey] asking critics to cite their best single test against astrology is misconceived in the first place. When testing a claim or theory, it is the cumulative evidence that is important. (UA 2022 p.717)

This sounds plausible but it is the authors’ way of dodging the challenge because there are no powerful and valid tests to cite on their own behalf – just flawed tests that can be falsified or numerous tests that, contrary to their intent, support astrology that have not been falsified. Cumulative evidence is important, and for the past fifteen years, it has been favouring astrology, which is why the authors have resorted to salvaging irrelevant tests.

3. Dean’s Meta-Analyses issues
Dean has attempted to combine the results of multiple independent studies into a series of statistical reviews to gain an overall view of astrological research in a series of meta-analyses.

I identified several fatal problems with Dean’s Meta-Analyses (UA pp.786,791,863-4):

  1. Apples are mixed with oranges. For example, Vedic (Indian), Chinese and Western are all added to the mix introducing an unacceptable level of methodological diversity.
    a. In the largest and least astrologically successful experiment listed, (as mentioned before) Professor Narlikar (2009) starts by asserting that his local Indian “astrology is fundamentally different from both Chinese and Western astrology.”
    b. Most of the eight participants in Smit’s test (2000) used Chinese divination (sometimes referred to as ‘astrology’) which is mostly not celestial based (e.g., the year of the Yin Water Rabbit).
  2. On his first listed meta-analysis, (UA pp.786-7,863) many studies are unrelated to Dean’s hypothesis that astrologers are unable to match birth charts to their owners.
  3. The authors oversimplify my criticism by claiming that I say Dean’s “use of effect sizes hides the importance of significance.” (UA p.718) The problem with the graphs is that they are cluttered with tiny samples where the Effect Size (see point 6) is not reliable. This would not be an issue if the studies were larger and confined to the same hypothesis and therefore comparable.
  4. Results such as subjects’ self-selection of their horoscopes in the Carlson test are included even though Carlson rejected the test as they were unable to select their psychological profile in a similar test (more later in the review) (UA p.864).
  5. Some of the Effect Sizes are still calculated using Cohen’s kappa which is a measure of rating and a flawed metric for ES (Currey, 2022a pp.52-53). It’s impossible to tell if the ES for Carlson’s astrologers’ three-way matching listed as .028 when Ertel’s updated calculation lists .10, is due to miscalculation or misreporting.
  6. As stated above, many studies are flawed or anecdotal or unpublished or all three! At least ten results came via “personal communication”.
  7. Too many tests are of a single individual’s competence rather than tests of astrologers. Out of seventy studies, fifteen (21%) tested only one astrologer.
  8. Data is duplicated. For example, eight similar tests from Press (1977) are counted separately as if they were different.
  9. The meta-analyses are cherry-picked. The meta-analysis of general tests of astrology (tests other than chart matching and lunar effects) in Astrology Under Scrutiny (2014, p.233) appears to have been cut from UA. This is unfortunate since astrology research has switched from trying to ‘prove’ the practice of astrology with matching tests towards investigating astrology through datasets. Otherwise, UA readers would have discovered that tests in the 21st century have small to medium effect sizes, viable sample sizes and as a result medium to high significance. For more details on the meta-analyses see (Currey 2014 pp. 54-55) Correlation 29.2

However, I salute Dean for being one of the first to have a go at meta-analysing astrological research. His work has helped make my own recent meta-analysis (Currey 2022b, pp.44-46) more reliable since the GIGO (garbage-in-garbage-out) factor is controlled. And just to be clear, in my analysis, effect and sample sizes are the key factors that respectively define the x and y axis. Significance can be inferred from the combination of these factors relative to threshold (alpha) values.

Science is not determined by democracy

When we carefully sift through the ‘thousand tests’, focusing on the most robust and plausible studies, a compelling picture emerges favouring astrology. Correlation Journal 34.2 (2022, pp.61-65) lists more than eighty studies supporting the fundamental notion of astrology. Let me delve into some of the best researched of these notable findings:

The sixteen Gauquelin tests (1955-1988); fourteen Gauquelin replications (1976-2021); Redhead Studies by Hill (1996 & 1998); The Carlson Test (1985) Revised (Ertel 2009). The New York Suicide Study by Press (1977) Revised (Currey 2021); Dean’s E&N Study (1981-1985) Revised (Currey 2023); Westran (2005 & 2021); Harris (2005); Ruis (2012); Tarvainen’s twenty papers (2012-2022); Kollerstrom (2015); Godbout (2020 & 2021); Douglas (2020 & 2021); Currey (2021) and Cochrane (2021).

As one might expect, the extreme reaction by Dean et al. to this Evidence List (2022b) is understandable as it threatens to undermine their entire book, Dean’s life work and his legacy. The authors’ harsh tone suggests that this list may have provoked them to experience feelings of cognitive dissonance.

“Given that hundreds of studies are documented in Tests of Astrology (which Currey quotes on p.8 but then ignores) and a thousand in the present work, plus countless more if the field includes physical effects such as people getting up at sunrise, to pretend that just 78 studies provide a “growing body of objective evidence” is ludicrous. It is cherry picking, the selection of good cherries to prove that a tree with mostly bad cherries is OK, so it gives a biased picture of the evidence base. In science anyone who adopted this approach would soon lose their job.

It gets even more ludicrous when the Evidence List is examined. If we reasonably expect the fundamental notion of astrology to involve astrologers reading charts for clients, only five of Currey’s 78 studies are relevant, yet arguably at least 126 (69+22+35) exist.” UA p.728

Again, let me unravel this:

  1. Scientific validity is not decided by democracy. Dean and his team argue that their self-proclaimed thousands of studies far outweigh “just 78 studies” listed. As explained, most of their alleged thousand studies have serious problems. The authors know this and as stated before, cannot point to a single negative study as exemplary and deserving of inclusion. One falsifiable but persistent successful study is worth more than a million flawed studies.
  2. The list is of evidence. The list is entitled The Evidence List – not the history of poor and failed tests from the last century that the authors love to dwell on. If the list is cherry picked for evidence as they believe and if they have any additional evidence that should in their view also be included, they are welcome to contribute. I will not be including tests of Chinese astrologers, magic tricks by Randi, straw man claims, anecdotes or tiny inappropriate samples.
  3. Consultations are not fundamental to astrology research. “His [Currey’s] list even includes studies of unlikely relevance to a consultation” (UA p.717). But my list clearly states that these tests “support the fundamental notion of astrology: that the positions and movements of celestial bodies correlate with life and physical processes on Earth.” (Currey, 2020, p.9 & 2022a p.61). Here, the authors have confused astrology with astrologers and then further removed their argument to the practise of astrologers reading charts in consultations. The Evidence List cites results that are consistent with astrology and, as most people know, astrology in principle is not limited to consultancy. Yet, their incorrect definition of astrology flipflops when it comes to labelling researchers who do not consult as astrologers! Dean et al. repeatedly describe independent researchers: Kyösti Tarvainen (UA p.274, 774), Ken McRitchie (UA p.451, 683, 702) and Peter Marko (UA p.783) as astrologers, to undermine their research by making them appear to be biased in the minds of impressionable readers.
  4. Making up rules as they go along. Dean et al. then describe ways to reject as many tests from the Evidence List as they can but without stating which ones! What they do say is that they don’t consider tests of serial killers to be relevant – even if insight into extreme human behaviour is useful to psychological astrologers. And yet, they cite several studies of serial murderers within their thousand tests (UA pp.24, 512, 607). Then they claim that the tests of dancers (Ferguson 1989) “fall apart when scrutinised” but the Evidence List references the re-examination by O’Neill (1989) which includes an expected significant negative ‘Gauquelin’ effect for eminent female dancers for Mars (p < .001; r = -.25). Moreover, Dean et al. are happy to include Ferguson and O’Neill in his list of independent replications of Gauquelin (p.195). Without specifics it is not possible to say which tests Dean et al. excluded but then were nevertheless included in their nebulous thousand studies. Such inconsistencies leave an impression that their internal rules are made up for convenience.
  5. Selection Bias Another false claim:His [Currey’s] supposedly positive results never involve practical significance (i.e. effect sizes) but statistical significance uncorrected for selection bias (which inflates that significance).” (UA p.717) Since they use the word ‘never’, just one example will refute their false claim. To be clear, selection bias occurs when a selected sample does not accurately reflect the target population. If I take four of my studies (in the list that follows), there is absolutely no question of selection bias and all results have practical significance both literally to practicing astrologers (apart from the Carlson Test) and as measured in terms of Effect Size. In every case, samples were selected by third parties with great care and professionalism. Inferences were always within the scope of each sample.
    i) Carlson data funded by CSICOP and published in Nature. Dean was involved. (p = .037; r = .57) (Ertel, 2009; Currey, 2023a)
    ii) Dean and two independent academics gathered data for the E&N study. (p < .0001; r = .15) (Currey, 2023b)
    iii) Nona Press & her NCGR colleagues collected suicide data where Dean collaborated. (p = .001; r = .18) (Currey, 2021b, p.44)
    iv) Alexander Boxer used public data on the births of US Supreme Court Justices. (p = .0004; r = .31; N=115) (Currey, 2022a p.44). This was the total population of the bar except for one justice without a known date of birth.
    Dean never complained about selection bias in Carlson, Press and his own paper when the results appeared to favour the null hypothesis. Now that they are shown to be significant with a medium to large effect size, Dean, rapidly shifts into reverse gear and repudiates his own samples!
  6. Ignore small effects at your peril. The authors claim Currey will “accept statistically significant results as positive regardless of how uselessly small their effect sizes might be.” (UA p.716). This refrain is repeated with other researchers throughout UA (pp. 146, 163,165, 238, 266, 471, 492, 617, 638, 711, 727). And there is a grain of truth there in that most single factor tests in astrology such as Sun Signs or Gauquelin sectors can yield only a low effect size (Currey, 2022a, p. 47).
    Where the UA authors are mistaken is that throughout science, an unexplained highly significant result with a small effect size should never be dismissed without investigation. In spite of the authors’ criticism of p values (UA pp. 704-711), this measure of significance informs how likely it is that a result is due to chance. In astrology, this probability calculation is critical to avoid the gambler’s fallacy (the belief that small samples with strong effects must be representative of the larger population).
    The authors never consider how effect sizes can be cumulative and how researchers can simulate consultant astrologers by combining small effect sizes to demonstrate a large effect.
    It is fortunate that this mindset is not tolerated in research into genetic inheritance. Studies into height variation revealed that the first forty DNA markers account for just 5%. This finding led to a search for more common variants with very small effects. It took 4.1 million participants to discover that 9,900 common markers account for 40% of the variation (Yengo, 2022).
    In the same way, astrologers interpret charts through combining and synthesising multiple factors. Some may not be aware of what they are doing, but I spent over twenty years investigating and refining this when writing software to simulate this process. If a chart has Aries rising, astrologers are unlikely, on this basis alone, to tell a client that they are competitive (Sakoan & Acker 1974) as there is a risk (due to a low Effect Size) that they may be wrong due to another planet, say Venus conjunct or in aspect. But if they see Mars rising in Aries, they now have two factors and the effect size may be high enough to risk raising the issue. This is a simplified example as the astrologer’s mind rapidly identifies more complex patterns.
    This should not need to be explained to most researchers in astrology, but the author’s approach to Effect Size suggests that they do not appreciate how astrology is practised. They feel qualified to judge astrologers but they do not ‘understand astrology’.
    To amplify this point, there are plenty of multi-factor and whole chart studies with medium to high effect sizes and high significance: r = .28 (Tarvainen 2021c), r = .31 (Currey 2021b), r = 40 (Douglas 2021) & r = .63 (Godbout 2020). This is set out in a meta-analysis of recent test results. (2022a)

Early days for the Astrology Research Program
This brings me to some issues where I agree with the authors. I largely concur with their need to emphasise Effect Size techniques, apart from their use of kappa which is both faulty and redundant (see Currey 2022a p.53). Also, they make the valid point that the studies require replication (UA p.717). Most studies replicate the models of astrological tradition although some are merely exploratory research. Works that have been replicated in tests are Gauquelin fourteen times, Hill, Westran, Godbout, Cochrane (two replications) and the Tropical versus Sidereal Zodiac for Western keywords (three times).
Nowadays, replication is hampered by two factors: data protection laws limit the scope for fresh samples and the difficulty in repeating unique situations. There are an almost infinite number of variables in human behaviour and the planetary positions “will almost certainly never repeat in our lifetime.” (Boxer, 2020 p.148).
The Astrology Research Program that exists today (McRitchie 2022) is still in its infancy. Yet, it has taken a leap ahead of the last century where experiments frequently suffered from artefacts, insufficient sample sizes and a lack of controls to a state where evidence comes via empirical tests without artefacts. Widespread replication is the next step.

4. The Dean Team
Funding Transparency in Astrological Research
In their comments about my role as an astrologer, researcher and editor, the UA authors claim that I have “a large financial stake in astrology” (UA p.716) and that my research is controlled by vested interests. They argue that my “conflict of interest … results in biased criticism.” (UA p.719)

While these kind of assumptions and personal assault is not relevant to my research or to my role as an editor, I would like to clarify my position. Since selling the Astrology Shop in 2001, astrology is no longer my primary source of income. Moreover, my research is self-funded and my work as editor of Correlation is only rewarded with complimentary copies of the journal.

Nevertheless, the focus of any evaluation should always be on the evidence or the validity of a claim, rather than the personal circumstances of the researcher. By exaggerating and misrepresenting my financial position to imply personal gain in the preamble to reviewing my research, the authors are using the fallacious tactic of ‘poisoning the well’. This is to undermine my credibility and the legitimacy of my research before anyone can read about it.

In view of the authors’ assumptions and claims about the motives of astrologers, it is only fair to expect greater transparency about the funding of their own publications. The widespread distribution of Understanding Astrology and its preceding books, without being commercially available, raises questions about their funding sources and the potential conflicts of interest associated with them.

Additionally, the close affiliation of Dean with sceptical organizations such as CSI (formerly known as CSICOP) raises further concerns about potential conflicts of interest. CSI/CSICOP has a well-documented history of flouting research rules (Rawlins, 1981). Moreover, the organization’s substantial annual turnover of $5 million (2015 accounts), with a significant portion dedicated to contributions and grants, further underscores the need for scrutiny.

Dean: the World’s Leading Critic of Astrology: A Mastermind or Team Player?

“Dean has always worked as part of a team. The implication that Dean works alone is incorrect.” (UA p.718)

Without wishing to take credit away from UA’s team of authors, not one of them can compare with Dean’s prolific and wide-ranging output. While the other authors have each made a significant contribution, Dr Dean is in a class of his own. Since 1985, he has been involved in nearly every sceptical investigation into astrology. Although he collaborates with fellow researchers, he is frequently credited as the sole author of his papers. This includes his four papers on Extraversion and Introversion published between 1981 and 1986 (UA pp.564-569, 576, 616-618). Notably, Dean played a pivotal role, either solely or in collaboration with various co-authors, in the largest and most definitive studies, including Gauquelin, the NY Suicide study, Carlson, E&N, and his Meta-Analyses.

Undoubtedly, UA was a collaborative effort. However, given that most of the book covers the period when Dean was most prolific (1977 to 2000), it is reasonable to infer that Dean is more than just a team player, despite the implication of the authors. He may have acted as the mastermind behind the overall approach and he certainly contributed significantly to the book’s content.

Dean is renowned as the world’s most dedicated and persistent critic of astrology. Since his disillusionment with astrology in 1982, his lifelong mission has been to debunk its claims. With charm and intelligence, the urbane Dr. Dean can transform into a Mr Hyde-like keyboard warrior. With the charisma of a skilled advocate, he can be remarkably persuasive, to the extent that he could seemingly convince anyone that the sky is green and the grass is blue, only to effortlessly switch their colours when blue skies are more advantageous. Yet, as every action creates an equal and opposite reaction, his criticism of astrology has led to a higher standard of research resulting in stronger evidence supporting astrology as researchers see through faults in his methods and rhetoric.

5. Gauquelin
Dean’s explanation of the Gauquelin Eminence Effect stretches credulity.
A significant portion of Understanding Astrology is dedicated to examining the research conducted by Michel and Françoise Gauquelin. The name “Gauquelin” appears 977 times in the index, highlighting their prominent role. In the final twenty-nine pages (UA pp.165-194) of their lengthy review, Dean embarks on a remarkable display of mental gymnastics. We are informed that the Gauquelins found a genuine but small eminence effect for certain planets in cadent houses and that it was replicated by studies run by sceptical organisations, but that the effect might not be due to astrology.

Brace yourself as you are about to fall into a rabbit hole.

Dean puts forth the proposition that the observed effect could be attributed to parents intentionally misreporting birth times to create an illusion that their child’s birth moment was auspicious for great eminence in a profession they would choose by its associated planet. It is reasonable to assume that some parents might adjust the time or even the date of birth to avoid certain superstitions, such as the 13th of the month or to signify the start of a new year. While this scenario seems plausible, extending this explanation to change the astrological placements of planets raises at least ten questions that lack credible answers.

  1. If parents assume that a planet in an auspicious position impacts their child’s life, why should they also believe that a fake position should also be auspicious?
  2. Why would parents prefer that a planet in a traditionally weak cadent house in their child’s horoscope and not in a traditionally strong angular house?
  3. If “astrology in 1880s France was no longer of intellectual interest” as claimed by the authors (UA p.109) why would sceptical scientists falsify their newborn’s horoscope in a superstitious belief that this would enable their child to later be invited to join the Académie de Médécine (a group which tested strongly for the effect)?
  4. If parents manipulate birth times to invoke the Moon, Mars, Jupiter and Saturn, why not the Sun (where Gauquelin found no effect)? The rising and setting positions of the Sun were listed in the Almanacs and our star, the Sun is considered a hugely important ‘planet’ in astrology.
  5. Dean points out how parents avoided the unlucky 13th of the month. Why then would they want to make planets that were categorised at the time as malefic, Mars and Saturn more prominent in their newborn’s imaginary horoscope?
  6. How did this conspiracy to defraud the authorities occur throughout Europe and the USA and yet, there is no evidence of even one described case where it occurred?
  7. How is it that parents lied in proportion to their child future eminence (Ertel, 1993)?
  8. If a few almanacs list the rising and setting of planets, how and why would parents know to use (just past) the culminating cadent house as well?
  9. As tampering with the birth time was no longer possible from the 1940s how do studies such a Cochrane & Fink (2010) with births mostly in the 1980s replicate the Gauquelin planetary effect?
  10. Why would parents observe precise data from almanacs and then so many of them round the time to the nearest hour or half hour when they came to register the time at the Town Hall?

This final question leads onto Dean’s pièce de résistance. He writes “Now the big one. Why is the planetary effect for precisely-recorded birth times half that for birth times rounded to the hour?” (UA p.190) His point is based on the dubious notion that those who misreport the time of birth have no need to time the birth to the minute as the planet is moving slowly. In fact, a rounded time “does not raise suspicions at the registry office like an exact time might.” (UA p.190) So, for Dean’s theory to work the more precise the birth time, the weaker the eminence effect. To update his book, The Gauquelin Effect, Reloaded Nick Kollerstrom (2023) checked this claim with the Gauquelin sports champions (N = 2,087). It turns out that 20.8% of those with the time listed to the minute had Mars in the two key Gauquelin sectors compared with 20.4% of those with the time listed to the hour. So, Dean’s claim of a difference in effect between the timed and the rounded birth times is without merit. This is yet another contrived and implausible line of reasoning that crumbles upon closer examination.

The Gauquelin results raise important questions for astrologers. Why did the Sun, Mercury, and Venus not feature in his eminence results? Why cadent and not angular houses contrary to tradition? Why is the Mars effect weaker from the 1940s – was it due to medical birth interventions? Were more C-sections and induced births weakening the natural cycle – as Gauquelin believed?
Yet, the Gauquelin eminence effect has been replicated by sceptical groups and by independent researchers around the world at least fourteen times (four of the eighteen examples below are questionable as genuine eminence effect replications).

Dean’s Parental Tampering conjecture has many of the hallmarks of a conspiracy theory but without collusion for malicious intent. It provides a template to explain an event that has no ‘rational’ explanation excluding astrology theory. It appeals to a love of fantasy and can be used to misinform. It lacks evidence and is unfalsifiable. And it relies on attribution bias where it is assumed that people think and behave in an irrational way in absolute secrecy.

Michel Gauquelin’s noteriety does not rest on the techniques that he discovered. He is famous because he was the first researcher to successfully defend his results against a thundering herd of sceptics determined to find fault and disprove his evidence … evidence that they believe threatens their ideological beliefs. As often happens, sceptics’ attempts to debunk his work led to even more replication (Ertel & Irving 1996). Most researchers would have caved in long before, but Gauquelin was determined and dedicated. And he had friends in high places such as Hans Eysenck, the most cited living psychologist in the world at the time. (Haggbloom, 2002) Nowadays the Gauquelins’ greatest legacy is the huge datasets of timed birth data that he and his wife, Françoise rigorously recorded. Their work has opened up a vast field of research.

Robust evidence supporting astrology seems to provoke an opposing reaction from those unwilling to acknowledge its validity, as we have seen especially among the UA authors. The response to Gauquelin’s compelling findings in the latter part of the 20th century was characterised by fierce opposition. The fact that the authors of UA resort to logical fallacies and personal assaults instead of addressing flaws or conducting proper statistical analysis only serves to reinforce the credibility of the evidence from the Astrology Research Program.

The irony of Understanding Astrology: A Critical Review of a Thousand Empirical Studies 1900-2020 becomes apparent when considering its title. Instead of a critical review the authors present fallacies and misinformation. The thousand viable empirical studies do not exist and while the authors understand the techniques of astrology, they lack a genuine understanding of the practice of astrology.

Many thanks to Roy Gillett, Dr Nicholas Campion, Renay Oshop, Vincent Godbout and Ken McRitchie for their advice and Jill Davies for proof reading.
Robert Currey

Boxer, Alexander (2020) A Scheme of Heaven. Astrology and the birth of Science. Profile Books
Carlson, Shawn (1985) A Double-Blind Test of Astrology, Nature Vol.318 pp.418-425
Cornelius, Geoffrey (1994) The Moment of Astrology: Origins of Divination
Cochrane, D. & Fink, D. (2010). A Reassessment of the Mars Effect and Other Planetary Effects, Cochrane’s MA Thesis University of Florida with advice from Professor Fink
Cochrane, David (2021) The Astrology of Bipolar Disorder. Cosmic Patterns Software
Currey, Robert (2011): . Correlation. Vol.27 (2)
Currey (2014) Review of Astrology Under Scrutiny. Correlation 29.2 pp.52-68
Currey (2020) Evidence List. Chronologically listed up to 2020 Correlation 32.2
Currey, Robert (2017) Can Extraversion & Neuroticism, as defined by Eysenck, match the four astrological elements? Correlation Vol.31 (1)
Currey, Robert (2018) Can Western Tropical Interpretations apply to the Sidereal Zodiac? Correlation Vol.32 (1)
Currey, Robert (2021a) Justice for the Supreme Court. Delving beyond a Sun Sign Test of 114 Justices, Correlation 33.2 pp.77-86
Currey, Robert (2021b), The New York Suicide Study – Reconsidered and Reversed, Correlation 34.1 pp.31-58
Currey (2022a) Evidence List 1960-2021. Correlation 34.2
Currey (2022b) Meta-Analysis of Recent Advances in Natal Astrology with a Universal Effect Size. Correlation 34.2 pp.43-56
Dean, (1977) Recent Advances in Natal Astrology. A Critical Review 1900-1976. Analogic: Subiaco, Australia
Dean, G. (1981) Planets and Personality Extremes Correlation 1(2) pp.15-18
Dean, G. (1985a)’Can astrology predict E and N? 1: Individual Factors, Correlation, Vol.5 #1, pp.3-17.
Dean, G. (1985b) Can astrology predict E and N? 2: the whole chart, Correlation, Vol.5 #2, pp.2-24.
Dean, G. (1986) Can astrology predict E and N? 3: discussion and further research, Correlation, Vol.6 #2, pp. 7-52. Includes meta-analyses of astrological studies.
Dean, G., Heukelom, Terpstra & Smit, R. (2014) Astrology Under Scrutiny: Close encounters with science. Wout Heukelom: Amsterdam
Dean, G., Mather, A., Smit, R. & Nias, D. (2016) Tests of Astrology, AinO publications, Amsterdam p.22 & p.262 also p.267
Dean, Mather, Nias & Smit (2022) Understanding Astrology. A critical review of a thousand empirical studies 1900-2020. AinO Publications: Amsterdam
Douglas, Graham (2020) Is the Gauquelin Effect born at conception? Michel Gauquelin’s intuition on geomagnetic micro-pulsations, Correlation Vol.33(1)
Douglas, Graham (2021) Replication of Ertel’s result on Sudden Infant Death Syndrome and Saturn in key sectors, Correlation 33.2 pp.87-93
Ertel, Suitbert. (1993). Puzzling Eminence Effects Might Make Good Sense. Journal of. Scientific Exploration, 7 (2), pp. 145–154
Ertel, Suitbert & Irving, Ken (1996) The Tenacious Mars Effect. The Urania Trust
Ertel, Suitbert (2009) Appraisal of Shawn Carlson’s Renowned Astrology Tests Journal of Scientific Exploration, Vol.23, No:2. pp.125-137
Ferguson (1989) Stars of Dance. Wheaton & Co.
O’Neill, Mike (1989) Analysis of Ballet Dancers in Gauquelin Sectors. NCGR Research Journal, Autumn Equinox, 21.
Godbout, Vincent (2020) An Automated Matching Test. Comparing Astrological Charts with Biographies. Correlation Vol.32 (2)
Godbout, Vincent (2021) To use or not to use midpoints, Correlation 33.2 pp.35-46
Greene, R., Harris, M. & Scott Macon, R. Another Look at Personal Validation. Journal of Personality Assessment Volume 43, 1979 – Issue 4
Hamilton, Teresa (1986) Review of Carlson’s Experiment, Astro-Psychological Problems Vol. 4.1
Harris, Pat (2005) Applications of astrology to health psychology: astrological and psychological factors and fertility treatment outcome [doctoral thesis]. Southampton, UK: University of Southampton.
Gould, Stephen Jay & Purcell, Rosamund (2001) Crossing Over: Where Art and Science Meet. Crown Publications
Haggbloom, S. JIg. (2002) “The 100 most eminent psychologists of the 20th century”. Review of General Psychology. 6 (2): pp.139–152.
Hill, Judith & Thompson, Jacalyn (1988) The Mars-Redhead Link: A Scientific Test of Astrology. Journal of National Council for Geocosmic Research
Hill, Judith (1996) Redheads and Mars: A scientific testimony. The Mountain Astrologer May 1996. pp.29-40
Kollerstrom, Nicholas (2015) The Eureka Effect. Correlation Vol.30 (1)
Kollerstrom, Nicholas (2023) The Gauquelin Effect, Reloaded. New Alchemy Press
Kurtz, Paul (2006) Science and the Public: Summing up thirty years of the Skeptical Inquirer, Skeptical Inquirer 33.4 In addition to founder Kurtz taking the credit, CSICOP fellows Richard Muller guided and funded the test and John Maddox, editor of Nature, secured the publication.
McRitchie, Kenneth (2014) Confirmation bias in the Wyman and Vyse experiment. Correlation, Vol. 29(2)
McRitchie, Kenneth (2016) Clearing the logjam in astrological research: Commentary on Geoffrey Dean and Ivan Kelly’s article ‘Is astrology relevant to consciousness and psi?’. Journal of Consciousness Studies, Vol. 23(9-10): pp. 153-179.
McRitchie, Kenneth (2022) How to think about the astrology research program: An essay considering emergent effects. Journal of Scientific Exploration, Vol.(4): pp. 706-716.
Press, Nona Gwyn (1997) An astrological suicide study. Journal of National Council for Geocosmic Research 2(2) pp.22-33
Narlikar JV, Kunte S, Dabholkar N, & Ghatpande P. (2009) A statistical test of astrology. Current Science (India) 96(5), 641- 643
Randi (1983) A small scale test of an astrological claim. Skeptical Inquirer 7.4 pp.6-8
Rochberg-Halton, Francesca (1991) The Babylonian Astronomical Diaries. Journal of the American Oriental Society Vol. 111, No. 2 (Apr. – Jun., 1991), pp.323-332
Ruis, Jan (2012) The Birth Charts of Male Serial Killers: Evidence of Astrological Effects. Correlation Vol.28(2) November 2012 pp.8-27
Sachs, A.J. & Hunger, H. (1988) Astronomical Diaries and Related Texts from Babylonia, Austrian Academy of Sciences, Vienna.
Smit, Rudolf (2000) Leo Knegt: A White Crow Beyond our Wildest Dreams? Listed as 2000 in UA and 2006 on the website:
Tarvainen, Kyösti (2011) Classical synastry works on the Gauquelins’ data, composite and Davison don’t, The Astrological Journal, Volume 53, Number 1, January/February 2011.
Tarvainen, Kyösti (2012a) Henning’s synthesis method shows validity of astrology in the Gauquelins’ data, Correlation 28(1) pp.25-43, 2012.
Tarvainen, Kyösti (2012b) A test of overall validity of astrological statements in the handbook by Sakoian and Acker, Correlation 28(1) pp.5-24
Tarvainen, Kyösti (2013) Favourable astrological factors for mathematicians, Correlation 29(1) pp.39-51.
Tarvainen, Kyösti (2014) Effects of Venus/Saturn aspects in marriages, Correlation 28(2): pp.7-14.
Tarvainen, Kyösti (2015). Do transits, solar arcs or progressions influence spouses’ will to have a baby? NCGR Research Journal, Volume 5: 58-70.
Tarvainen, Kyösti (2015) A study of Major and Minor Aspects in theologians’ charts. Correlation, Vol.30(1)
Tarvainen, Kyösti (2016). The Moon’s Nodes in the synastry of the Gauquelins’ couples. Correlation 30(2): 27-37.
Tarvainen, Kyösti (2017) Planets are strong also according to ordinary astrology in the Gauquelins’ data. Correlation Vol. 31(1)
Tarvainen, Kyösti (2017). On Lawyers’ Astrological Factors. Journal of Research of the American Federation of Astrologers, Vol 17.
Tarvainen, Kyösti (2017) Chart Rulers work in the Gauquelins’ data. Correlation Vol.31 (2)
Tarvainen, Kyösti (2018). A Study of the Part of Fortune on the Gauquelin Data. Journal of Research of the American Federation of Astrologers, Vol 18.
Tarvainen, Kyösti (2018) On the Astrological Polarity of Extravert and Introvert Groups, Correlation Vol. 32 (1)
Tarvainen, Kyösti (2020) Estimation of aspect orbs by the computer, Correlation Vol. 32 (2)
Tarvainen, Kyösti (2021) A study of midpoints in theologians’ charts, Correlation 33.2 pp.47-54
Tarvainen, Kyösti (2021), Statistical Studies have started to advance astrological techniques, Correlation 33.2 pp.55-64
Tarvainen, Kyösti (2021), Confirmation of Ptolemy’s 5-degree rule for Koch and Equal Houses, Correlation 34.1 pp.9-16
Tarvainen, Kyösti (2021) Guessing aspects from interviews and obituaries, Correlation 34.1 pp.77-88
Wyman, A. J., & Vyse, S. (2008) Science versus the stars: A double-blind test of the validity of the NEO Five-Factor Inventory and computer-generated astrological natal charts. Journal of General Psychology, 135(3), pp. 287–300.
Yengo, L. (2022) Discoveries and lessons from a genome-wide association study of human height in >5 million individuals. The Netherlands: Wageningen Academic Publishers.