The 1985 Nature Double-Blind Test of Astrology

One hundred ninety-two scientists sign a public statement calling astrologers charlatans. Nineteen of them have Nobel Prizes. And one man reads it, agrees with every word of the science... and refuses to put his name on it.

Refuses? Who turns down THAT guest list?

Carl Sagan. Hold onto him, because he's the end of this story. The start is nineteen eighty-five, when the journal Nature prints a paper with a title that sounds like a magazine quiz. A Double-Blind Test of Astrology.

Nature published a study on astrology? That feels like the wrong building.

That's what everyone gets wrong. Scientists didn't ignore astrology. They tested it. Properly.

Okay. Who's running it?

A researcher called Shawn Carlson. And the design is beautiful, because he doesn't impose it from outside. The astrologers are nominated by the National Council for Geocosmic Research, an astrological body. And they advise on the test to make sure it's fair.

Hang on. The astrologers helped BUILD the experiment?

They even chose the measuring stick. The California Psychological Inventory, a standard personality test, which the astrologers themselves picked as the instrument best matching what they believed they could read in a chart.

So there's no ambush. No skeptic going, right, prove it, clock's running.

None. And here's the detail I keep coming back to. Before any data existed, before anyone knew which way it would fall... the astrologers agreed, in writing, that the protocol was a fair test of astrology.

Which means you can't walk it back after.

Twenty-eight astrologers, from Europe and the United States. Between them, one hundred sixteen natal charts. For each chart, three personality profiles. One belongs to the real person. Two don't. Pick your first choice and your second.

And double-blind means the person handing it over...

Doesn't know either. Samples numbered, sealed, guarded. Nothing leaks through a glance or a flicker in someone's voice.

So blind chance gets you one in three.

One in three on a first pick. Carlson's conclusion: natal astrology, as practised by reputable astrologers, performed no better than chance.

Brutal.

It became one of the most cited studies ever to claim a refutation of astrology. And astrologers felt it. In their own words, it kept undermining the credibility of every astrological consultant and school... for decades.

Gavel down, then.

Not quite. Because what happened next is more revealing than the result.

Go on.

Astrological researchers went back into the numbers. Ken McRitchie, in an astrology journal, argued the design was skewed, that Carlson ignored prior studies, and that a reanalysis of the rating test actually produced results consistent with astrology. And one astrologer Carlson thanked for valuable suggestions later said, quote, Carlson followed none of my suggestions.

Shocking. The losing side found a flaw.

Sure. But look at what they had to do to fight back. Argue about effect sizes. Blinding. Criteria set in advance. They had to step onto science's turf and play by science's rules.

Huh. So the complaint is itself a win for the method.

That's exactly it. Science didn't fund astrology. It did something stranger. It let astrology write the exam.

More respect than most pseudoscience gets.

Which is why, ten years earlier, Sagan wouldn't sign. Nineteen seventy-five, the magazine The Humanist runs that statement, Objections to Astrology. The astronomer Bart Bok leads it. Crick signs. Linus Pauling signs. It says the time has come to challenge, directly and forcefully, the pretentious claims of astrological charlatans.

And Sagan... what, secretly liked horoscopes?

He thought astrology had no validity whatsoever. He explains it later in The Demon-Haunted World. He couldn't sign because the tone was, in his word, authoritarian.

Okay, but what's the actual objection?

Two things. The statement speculated about the psychology of believers instead of refuting the beliefs. And it leaned on there being no known mechanism. Sagan pointed out that when Alfred Wegener proposed continental drift, there was no known mechanism for that either. And Wegener was right.

So the great debunker is standing there going, careful, that exact argument has burned us before.

What he said he WOULD have signed was a statement describing and refuting the actual tenets of astrology. That, he thought, would be far more persuasive.

And ten years later Carlson did it. With envelopes.

With envelopes. Authority says trust us. Evidence says check us. And the real line between the two fields isn't telescopes versus star signs... it's whether you'll write down, in advance, the result that would prove you wrong.

And astrology never writes that down.

It never has to. Which is how it survives everything, including Nature. The sky doesn't know your birthday. But somebody sealed one hundred sixteen envelopes to make sure... and that impulse is the best thing our species does.