[PeterWhittaker]

The lead researcher, quoted in TFA:

"The correlation is moderate, so our findings are interesting, but it does not mean that parents should worry if their child draws badly.

"Drawing ability does not determine intelligence, there are countless factors, both genetic and environmental, which affect intelligence in later life."

[QuantumChaos]

These are just boilerplate disclaimers.

>The correlation is moderate, so our findings are interesting

A fair comment

>but it does not mean that parents should worry if their child draws badly.

Just an irrelevant disclaimer.

>Drawing ability does not determine intelligence, there are countless factors, both genetic and environmental, which affect intelligence in later life.

Just a disclaimer to rule out "determinism", which is itself a meaningless concept in the probabilistic world we live in. Given the correlation they discovered, it is accurate to say that drawing ability predicts intelligence to some degree.

[lutusp]

> Given the correlation they discovered, it is accurate to say that drawing ability predicts intelligence to some degree.

Not in a scientific sense. For science, the existence of the correlation isn't enough to argue for a predictive relationship. For science, someone would have to design a test in which the drawing was proven to anticipate later developments, rather than accompany them passively (and with a rather marginal p-factor). In a human study with ethical standards in place, this is quite impossible.

In the strictest scientific sense, a study like this would have to show a mechanism, a cause, that connected particular drawing traits with later intelligence. Merely observing a correlation without a proposed explanation is suspect.

For example, someone might say, "The development of brain area X by age Y simultaneously shows itself through a particular drawing ability -- to the exclusion of other explanations -- and has been shown to be a precondition for specific intellectual processing ability Z at age 14." Obviously a study like this can't possibly reach those heights while remaining within its budget and while adhering to prevailing ethical standards and neuroscientific knowledge.

I emphasize I am not advocating what I say next, it's only hypothetical, to make a point. An imaginary study could say, "We snipped out a small section of brain tissue from region Q, and saw (a) a decline in drawing ability, and (b) a subsequent decline in overall intellectual capacity later in life."

But you know what? Such things are done all the time in animal studies, unfortunately with dubious relevance to humans. Also, my hypothetical study would still not explain why that result came about, only that the hypothetical snipping was correlated with a specific outcome. Remember that proposing and then testing explanations is the essence of science.

[thaumasiotes]

> For science, the existence of the correlation isn't enough to argue for a predictive relationship. For science, someone would have to design a test in which the drawing was proven to anticipate later developments, rather than accompany them passively

You're confusing a "predictive" relationship with a "causative" relationship. A correlation and a predictive relationship are the same thing.

[lutusp]

> A correlation and a predictive relationship are the same thing.

Not at all. Do puddles predict rain, or accompany it? A prediction is specific, and distinct from a simple correlation. A prediction assumes the existence of a cause-effect relation between the measured property and something predicted in the future, even if (as in this case) the mechanism connecting them isn't known.

Prediction implies cause and effect. Exposure to a virus predicts infection in some of those exposed -- it's more than a simple correlation.

Inebriation predicts traffic accidents. Sexual activity predicts pregnancy and STDs. And so forth. These aren't simple correlations.

> You're confusing a "predictive" relationship with a "causative" relationship.

No, I'm asserting that that is what it means, as do all who use the word "prediction" in this context.

[thaumasiotes]

See http://www.thefreedictionary.com/predictor+variable , or http://www.theanalysisfactor.com/the-many-names-of-independe...

Pregnancy predicts sexual activity just as sexual activity predicts pregnancy (actually, better). The reference to the future is that you test the second variable in the future, not that it receives its value in the future.

From the second link:

> Predictor Variable: It does not imply causality. A predictor variable is simply useful for predicting the value of the response variable.

[lutusp]

> Pregnancy predicts sexual activity just as sexual activity predicts pregnancy (actually, better).

This merely says that the use of "predicts" in this context is meaningless, since in common usage "predicts" implies a one-way relationship.

I see from your second link that a definition has been crafted that undermines the word's common meaning. So it goes in language, an art, not a science, and one in which words mean whatever people think they mean, as with the sad case of "literally", which often means "figuratively".

http://www.merriam-webster.com/dictionary/literally

[thaumasiotes]

They didn't discover a correlation between drawing ability and intelligence; as the article admits, the Draw-A-Man test has been in use since the 1920s. They established a correlation between DAM scores at age 4 and scores on other IQ tests at age 14. Which is a little interesting (since the most common rule of thumb I've heard is that IQ scores are near-totally unreliable before age 6), but not very.