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First, to define what a Simian Line is, I will quote from the Wikipedia page.

In humans, a single transverse palmar crease is a single crease that extends across the palm of the hand, formed by the fusion of the two palmar creases (the heart line and the head line) that people typically have. Because it resembles the usual condition of non-human simians, it is also known as a simian crease or simian line, although these terms have widely fallen out of favor due to their pejorative connotation.

I am using the term simian line in the question because that is all I have ever heard it called.

There are various claims (mostly from palm readers) that simian lines tend to have certain personality characteristics attributed to them. There have also been some studies showing a potential correlation between simian lines and criminal behaviour, for example:

Various studies have indicated that the simian crease (or a 'single radial base crease') is more often seen in the hands of criminals, juvenile deliquents, and even murderers. In the same year a very interesting pioneering study was presented by Ramesh Chaube (in: "Application and Methodological Perspectives in Dermatoglyphics", 1971), which revealed that the 'single radial transverse crease' (which includes the 'complete' simian line + some of it's related variants) is much more often seen in the hands of various types of criminals (29.25% vs. 11.81% in controls).

Taken from here.

Is there anything to support a correlation between personality types/characteristics and simian lines?

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Well researched question, though dup of skeptics.stackexchange.com/questions/615/… methinks. –  Zano Jan 25 '12 at 7:52
    
@Zano I think it is a separate question. Palmistry is the idea that you can tell aspects of a persons personality or future from the palm lines that everybody has. I'm asking if there is any correlation between personality and a distinct type of palm line that only a minority of the population have as is claimed. I also note simian lines are correlated with various genetic disorders and other biological conditions, mainly heart disease. –  Sonny Ordell Jan 25 '12 at 7:58
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@Zano, No, I don't consider it the same thing. The line is on the palm so it isn't surprising it comes up in palmistry and that palmists are some of the people making the claim. The general question on palmistry wouldn't apply as everybody has palm lines but only ~10% of the population have simian lines. Further, simian lines are correlated with various other things while palm lines are not, to my knowledge. The other question isn't useful at all because it isn't specific to simian lines. –  Sonny Ordell Jan 25 '12 at 8:15
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@Zano except it wouldn't. I don't understand why you don't see the distinction. Everybody has palm lines. Only 10% have a single simian line with 5% having one on both hands. Palm lines are not correlated with anything, because everybody has them. Simian lines are correlated with various things because not everybody has them. An answer to this question would not be a valid answer to the more general question and vice versa. Do you see why it's different? –  Sonny Ordell Jan 25 '12 at 8:34
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It's all bullocks. Next. :P –  Brightblades Jan 25 '12 at 14:52

1 Answer 1

up vote 7 down vote accepted

There are some physiological conditions that may be tied to overall structure of one's hands, however these are not very reliable correlations. For instance, there may be a correlation between finger length and exposure to pre-natal testosterone, which in turn may be correlated to aggression and masculinity (PDF).

Hand-grip strength also showed a correlation to male behaviour in this paper (PDF).

Handgrip strength (HGS) is a noninvasive measure of physical health that is negatively correlated with disability, morbidity, and mortality rates in adults. Highly heritable, HGS is indicative of blood testosterone levels and levels of fat-free body mass. In this study, we investigated whether HGS was related to measures of body morphology [shoulder-to-hip ratio (SHR), waist-to-hip ratio, and second-digit-to-fourth-digit ratio (2D:4D)], aggressive behavior, and sexual history in 82 male and 61 female college students. Results showed that HGS was correlated with SHRs, aggressive behavior, age at first sexual intercourse, and promiscuity in males but not in females. HGS appears to be an honest signal for genetic quality in males.

Specifically regarding your question on palm lines. A student at the University of Texas is making a study of the simian line and palm creases, however I have not found the results. In particular, they are looking for (emphasis mine):

The palm lines do not have a direct implication on the success rate of mating and reproduction, nor on development and health, hence palm line pattern is not actively sought for by Natural Selection. Any mutation that causes change in palm line pattern is not specifically selected or rejected because of the palm line pattern, but because of their other effects on other parts of the body or other stage of development.

The student goes on to say:

Statistically significant correlation between the palm line pattern and the disease is looked for using methods from data mining including, but not limited to, artificial neural networks. Our hypothesis of the correlation so obtained is then tested on another large set of people not known to have this disease or not. Those identified with the disease are then verified using traditional methods of DNA testing.

Zano mentioned a Swedish study, and I found this report that does say that there may be some correlation with the simian line.

People with Down syndrome typically have short, stocky bodies with thick hands and feet. Their hands also commonly have a "simian crease", which is a crease in the palm that runs completely from one side of the hand to the other.

However, it doesn't seem to make clear the correlation, and specific genetic cause of that line in this article.

This paper (PDF) mentions the simian line once in 106 pages, however it doesn't offer any useful conclusions.

Although, Columbia University statistics warn against attributing too much in terms of correlation, since it is easy to lie with statistics.

BOTTOM LINE: There may be some correlation; however, the mechanisms and studies are still ongoing. Beware of anyone saying that because of "X" therefore "Y" in this case. As is all too often the case, these things are much more complicated than simple correlations.

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I've downvoted this. The claim has nothing to do with palmistry and certainly not cold reading. It's about a distinct and somewhat rare physical trait and a possible correlation with personality. A correlation between simian lines should be just as possible as between red hair and temperament. Also, the answer should be specific to simian lines, not hand or palm stuff in general. –  Sonny Ordell Jan 28 '12 at 20:55
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@SonnyOrdell Then perhaps you should edit your question? At least half of the question's body has quotes from palmistry sites... Those distract from the remainder of the question (which I also addressed in my answer with the ever popular "we're not sure, yet"). And the paper I cited in a comment on the "red hair" questions seems to indicate there really is NO correlation to hair colour and personality. –  Larian LeQuella Jan 28 '12 at 21:04
    
The claims are coming from palmistry sites, simply because they are the most abundant. Since simian lines are on the palm palmists are going to take note of that. However just because a claim is made by a questionable source doesn't mean there isn't something to the claim. Basically, your answer takes time to show why palmistry is bunk when I'm not asking about palmistry. I feel this question should be treated the same as the redheads question. -- I will however look for non palmistry sources for claims. –  Sonny Ordell Jan 28 '12 at 21:10
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@SonnyOrdell I still suggest that they be removed though, since they are distracting... There is a lot of chaff on the internet, and Palmistry ranks up there with some of the stinkiest chaff.... And just because a claim is common is no indication of its validity. Which is why I spent time debunking palmistry... A lie is a lie if millions believe it, and the truth is the truth if no one believes it. And questionable sources for claims without any other sources may be your first clue as to the validity of the claim. –  Larian LeQuella Jan 28 '12 at 21:28
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@SonnyOrdell Besides, attempting to use external traits as some sort of clue to behaviour and personality has a long and distinguished history of being bunk as well. Just think of phrenology! –  Larian LeQuella Jan 28 '12 at 21:29

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