Saturday, August 07, 2010

Bad News for the Genetics of Personality

CREDIT: RYAN SNOOK (from Holden, 2008).


The latest search for genetic variants that underlie differences in personality traits has drawn a blank (Verweij et al., 2010). The researchers conducted a genome-wide association study using personality ratings from Cloninger's temperament scales in a population of 5,117 Australian individuals:
Participants' scores on Harm Avoidance, Novelty Seeking, Reward Dependence, and Persistence were tested for association with 1,252,387 genetic markers. We also performed gene-based association tests and biological pathway analyses. No genetic variants that significantly contribute to personality variation were identified, while our sample provides over 90% power to detect variants that explain only 1% of the trait variance. This indicates that individual common genetic variants of this size or greater do not contribute to personality trait variation, which has important implications regarding the genetic architecture of personality and the evolutionary mechanisms by which heritable variation is maintained.
But it's still fun and popular for some science writers to assert that personality traits are "hard wired" into our brains, like there's really A Brain Circuit for Bungee Jumping? [thanks for the exciting new info, ScienceNOW.] In reality, some of the major early findings in personality genetics, such as an association between Novelty Seeking and the Dopamine D4 Receptor gene (Benjamin et al., 1996; Ebstein et al., 1996), have failed to replicate (Gelernter et al., 1997; Paterson et al. 1999; Strobel et al., 2002). Fortunately, others writers have pointed out the increasingly obvious difficulties of this endeavor, as did Constance Holden in Parsing the Genetics of Behavior:
For some of us, it's satisfying to attribute social awkwardness to anxiety genes or to think that the driver who cuts off other cars as he zips across lanes is pumped up by the "warrior" gene. Was it a bad dopamine receptor gene that made author Ernest Hemingway prone to depression? Can variations in a vasopressin receptor gene--a key to monogamy in voles--help explain adulterous behavior?

But as scientists are discovering, nailing down the genes that underlie our unique personalities has proven exceedingly difficult. That genes strongly influence how we act is beyond question. Several decades of twin, family, and adoption studies have demonstrated that roughly half of the variation in most behavioral traits can be chalked up to genetics. But identifying the causal chain in single-gene disorders such as Huntington's disease is child's play compared with the challenges of tracking genes contributing to, say, verbal fluency, outgoingness, or spiritual leanings. In fact, says Wendy Johnson, a psychologist at the University of Edinburgh, U.K., understanding genetic mechanisms for personality traits "is one of the biggest mysteries facing the behavioral sciences."

Nonetheless, unscrupulous businesses like My Gene Profile (which offers the "Inborn Talent Genetic Test" for the low low price of $1,397) have capitalized on the public's desire for simple explanations. Now you can find out whether your child has the Split Personality Gene! The Propensity for Teenage Romance Gene! The Self Detoxifying Gene!

Returning to the current study, the authors cast a genome-wide net to find genetic variants related to the four dimensions of temperament identified by Cloninger in his Temperament and Character Inventory (TCI), a 240 item self-report questionnaire. As described by Verweij et al., (2010):
Novelty Seeking reflects the tendency to respond strongly to novelty and cues for reward as well as relief from punishment, and is thought to play a role in the activation or initiation of behaviours. Harm Avoidance reflects the tendency to respond strongly to aversive stimuli, which leads to learned inhibition of behaviour, and is thought to play a role in the inhibition or ceasing of behaviours. Reward Dependence reflects the tendency to react strongly to rewards and to maintain behaviours previously associated with reward or relief of punishment, and is thought to play a role in the maintenance or continuation of behaviour. Persistence reflects the tendency to persevere despite frustration and fatigue.
The participants completed a short form of Cloninger's (1986) original Tridimensional Personality Questionnaire (TPQ).1 The fourth dimension of temperament -- Persistence -- was constructed using a small subset of the Reward Dependence questions. The 1986 version of Cloninger's biosocial theory of personality associated Novelty Seeking with low dopamine activity, Harm Avoidance with high serotonin activity, and Reward Dependence with low noradrenaline activity. These were thought to be independent and heritable aspects of personality that influence responses to reward, punishment, and novelty. The TPQ was later revised to include Persistence and also three character dimensions (Self-Directedness, Cooperativeness, and Self-Transcendence) to form the basis of the TCI (Cloninger et al., 1993).

Cloninger's theory of personality is not without its critics. In 2008, Farmer and Goldberg challenged the psychometric validity of the TCI in a target article and in a wonderfully titled reply to Cloninger. A trenchant quote from the latter (Farmer & Goldberg, 2008) is below:
Overall, several core theoretical assumptions and predictions associated with the psychobiological model and TCI-R assessment are either non-falsifiable, in conflict with each other, or not supported by empirical evidence.
So the question arises, are we dealing with a flawed set of personality constructs to begin with? No matter. The scales are widely used, so we'll go on.

For genotyping, single nucleotide polymorphisms (SNPs) across the entire genome were tested for association with each of the four traits. The Illumina and Affymetrix platforms were used. [Those technical and statistical methods are beyond the scope of this blog, so I will leave it to someone else to describe and critique the genotyping aspects of the paper.] Stated succinctly, the results showed that:
No SNPs reached genome wide significance (α = 7.2*10-8) and the SNP with the lowest p-value for each personality scale explains less than 0.5% of the total variance.
None of the previously identified candidate genes (e.g., serotonin receptor gene, D4 receptor gene) were close to showing a significant relationship with any trait, nor were any of the SNPs with the lowest p value for each trait "in or close to a gene of known relevant function." The authors conclude that "common genetic variants do not contribute substantively to variation in personality." How can this be the case, when 30-60% of the variance in personality should be explained by genetics?
This raises the question of "missing heritability"... Missing heritability has been observed to a large extent in almost all complex traits. Proposed explanations focus on: many variants of very small effect that are yet to be found; rare variants that are poorly detected by available genotyping arrays that focus on variants present in at least 5% of the population; structural variants poorly captured by existing arrays, such as copy number variations; and low power to detect epistasis (interaction between genes). Newer technologies (e.g. whole genome sequencing) and novel statistical approaches combined with larger samples and meta-analyses will contribute to our understanding of the genetic architecture of complex traits.

So don't rush out and spend $1,397 on the Inborn Talent Genetic Test just yet...


Footnote

1 Note that the participants did not complete the full TCI. Did that make a difference? Perhaps not, since two previous GWAS failed to find anything for Eysenck's Neuroticism scale or for the Big Five personality traits.

References

Benjamin J, Li L, Patterson C, Greenberg BD, Murphy DL, Hamer DH. (1996). Population and familial association between the D4 dopamine receptor gene and measures of Novelty Seeking. Nat Genet. 12:81-4.

Cloninger CR. (1986). A unified biosocial theory of personality and its role in the development of anxiety states. Psychiatr Dev. 4:167-226.

Cloninger CR, Svrakic DM, Przybeck TR. (1993). A psychobiological model of temperament and character. Arch Gen Psychiatry 50:975-90.

Ebstein RP, Novick O, Umansky R, Priel B, Osher Y, Blaine D, Bennett ER, Nemanov L, Katz M, Belmaker RH. (1996). Dopamine D4 receptor (D4DR) exon III polymorphism associated with the human personality trait of Novelty Seeking. Nat Genet. 12:78-80.

Gelernter J, Kranzler H, Coccaro E, Siever L, New A, Mulgrew CL. (1997). D4 dopamine-receptor (DRD4) alleles and novelty seeking in substance-dependent, personality-disorder, and control subjects. Am J Hum Genet. 61:1144-52.

Farmer RF, Goldberg LR. (2008). Brain Modules, Personality Layers, Planes of Being, Spiral Structures, and the Equally Implausible Distinction between TCI-R "Temperament" and "Character" Scales: A Reply to Cloninger. Psychol Assess. 20:300-304.

Herbst JH, Zonderman AB, McCrae RR, Costa PT Jr. (2000). Do the dimensions of the temperament and character inventory map a simple genetic architecture? Evidence from molecular genetics and factor analysis. Am J Psychiatry 157:1285-90.

Holden C (2008). Parsing the genetics of behavior. Science 322:892-5.

Paterson AD, Sunohara GA, Kennedy JL. (1999). Dopamine D4 receptor gene: novelty or nonsense? Neuropsychopharmacology 21:3-16.

Strobel A, Lesch KP, Hohenberger K, Jatzke S, Gutzeit HO, Anacker K, Brocke B. (2002). No association between dopamine D4 receptor gene exon III and -521C/T polymorphism and novelty seeking. Mol Psychiatry 7:537-8.

Verweij, K., Zietsch, B., Medland, S., Gordon, S., Benyamin, B., Nyholt, D., McEvoy, B., Sullivan, P., Heath, A., Madden, P., et al. (2010). A genome-wide association study of Cloninger's Temperament scales: Implications for the evolutionary genetics of personality. Biological Psychology DOI: 10.1016/j.biopsycho.2010.07.018



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32 Comments:

At August 07, 2010 7:25 PM, Blogger SustainableFamilies said...

This was really informative. I hate that being adopted means I'm a science experiment, but really it's true.

I grew up with ZERO genetic relatives and have since met all of them (at age 18).

The parallels are BIZARRE. My dad and I can talk existential philosophy and the meaning of the universe for hours... the thought patterns are so eerily similar. The same with my mother.

We have the same voice. The same accent. She's from South Dakota and I've been raised in Texas my whole life.

And my half sister... who was also adopted at birth into a family of non-genetic family members?

Our life journeys are the same. She was in conservative land and yet we both wound up discovering that we have the same hyper-sensitives to our surrounding, the same EXACT fears that seem to impede us in similar ways... and not only that but we came up with the same solutions.

I get my dyslexic typing from my dad.

But I resent this whole idea that genes can be mapped out in the manner that scientists seem to believe they can be mapped out. No I don't subscribe to the static theory of genes being set from exact duplications of the parents with the exceptions of a few tiny TOTALLY RANDOM genetic mutations.

I get there is a lot of evidence this theory holds some weight, but this is an organic process. And genes aren't as static as they seem, from much of what I've read. Think about how many hormones and biological changes happen in our bodies when we experience stress, love, fear, terror, horror...

What happens to an infant when those physiological processes are happening while that being is being created in the womb? Being adopted has made this field of research a source of deep fascination for me, however as I remain agnostic in my faith, I remain "agnostic" towards scientific "fact" in any field. Fact simply means no one has proven it wrong. Yet.

 
At August 07, 2010 9:22 PM, Blogger Razib said...

great post. but i think you're a little hard on those who say personality is "hard-wired." there's more robust evidence that the tendencies seem highly heritable (the fact that the measurement of the traits or their constructs kind of suck should indicate that the heritabilities low ball, right?). we just might not find large effect QTLs.

 
At August 08, 2010 3:46 AM, Blogger petrossa said...

Aspergers is a maybe not a personality as such, but it sure causes the afflicted to display the same range of personality disorders. Where does a personality disorder become a personality? I believe the definition of what constitutes personality is to broad to be useful as a determinant. So logically you can't find genetic markers to account for it.

 
At August 08, 2010 11:50 AM, Anonymous Anonymous said...

What is missing from much of the work to identify specific genes associated with various phenotypes is consideration of the environment. Both human studies and those in other animals clearly indicate that both genes and environments matter. Studies that fail to capture environmental or experiential variation are probably going to miss on identifying relationships between genes and behaviors, especially for complex traits.

 
At August 08, 2010 12:33 PM, Blogger The Neurocritic said...

SustainableFamilies - I'm glad my post was able to inspire some personal reflection.

Razib - Thanks for your comment. As for the "hard-wired" line, I was mostly referring to the popular press, which can blow these things out of proportion.

Anonymous - While it's true that gene X environment interactions are very important, this information isn't always available for GWAS. What self-report questionnaire on upbringing/environment would you suggest is suitable for large-scale studies with thousands of participants?

petrossa - There is some discussion about overlap between schizoid personality in childhood and Asperger's, although others suggest the two are distinct (Lifelong eccentricity and social isolation. II: Asperger's syndrome or schizoid personality disorder?).

 
At August 08, 2010 12:50 PM, Anonymous Anonymous said...

Neurocritic, agreed that it may be difficult to include environmental or experiential variables in a large n, human study. But if failing to include them means that the results are equivocal at best, then it is worth rethinking how the question should be approached and what the data mean. At the very least, the caveat should be given real consideration in discussing the results and real consideration in designing studies to move the field and our understanding forward.

And there are large human studies that make the effort to include at least some kind of measurement of environmental or experiential factors. It is exactly those studies which have demonstrated that both genes and environments matter.

 
At August 08, 2010 2:01 PM, Anonymous Keith Grimaldi said...

Anon is correct about Gene x Environment. Studies on the serotonin transporter gene variant (SLC3A4 - 5HTTLPR) suggest that adverse personality effects are associated with the S allele but only when the environment is "stressful" (just one e.g. http://bit.ly/9GTNtv).

Environment is hard to measure, I suppose that's why it's missing from most GWAS. I hope it will appear in the next round, it can't be ignored.

 
At August 08, 2010 2:09 PM, Anonymous Anonymous said...

With personality appearing so overwhelmingly heritable - with so many examples and anecdotes - the fact that GWA studies do not show any correlations with personality and genes tells a simpleton like me that we either inherit something more than just genes from our parents, that identical genes do not necessarily express themselves identically or personality is in the brain which forms with distinct noise and varying expression prior to birth. I simply can't subscribe to the Ghost in the Machine. It's hardwired somewhere.

 
At August 08, 2010 2:13 PM, Anonymous Keith Grimaldi said...

Sorry, typo, Serotonin transpoerter gene is SLC6A4

 
At August 08, 2010 2:53 PM, Anonymous Anonymous said...

Excellent article, well done!
- Dave Curtis

 
At August 08, 2010 4:24 PM, Blogger knd said...

Title of this post should have been Bad News for the **SNP** Genetics of Personality...

as you rightly quote the authors on the fact that other yet-to-be-explored features of the genome might bear significant relation to personality.

 
At August 09, 2010 12:55 AM, Blogger The Neurocritic said...

Anonymous and Keith Grimaldi - I agree, it's critical to look at Gene x Environment interactions. But it's not easy. Did you see the new article by Zammit et al., Misconceptions about gene–environment interactions in psychiatry? They're downright pessimistic:

"Misunderstandings surrounding the study of gene–environment interactions are very common. Given the large increase in the number of studies examining interactions in recent years, this raises serious concerns about the value of time and resources spent in these endeavours. In this article we discuss why, despite frequent claims to the contrary, studies of gene–environment interactions are very unlikely to enhance our understanding of disease aetiology or prevention."

Another failure to replicate: a recent meta-analysis in JAMA (Risch et al., 2009) found that the serotonin transporter gene variant (5-HTTLPR polymorphic region) was not linked to an increased risk of depression, either alone or in combination with stressful life events. This study examined 14 prior papers, including a well-known one by Caspi et al. (2003) in Science.

 
At August 09, 2010 1:22 AM, Blogger The Neurocritic said...

Dave Curtis - Thanks.

knd - The recent post at Gene Expression, Genome-wide association studies work, was interesting. The author linked to some Correspondence in Cell critiquing the recent Jon McClellan and Mary Claire King essay “Genetic Heterogeneity of Human Disease”:

Successes of Genome-wide Association Studies

Strategies for Genetic Studies of Complex Diseases

 
At August 09, 2010 5:02 AM, Blogger Kevin Mitchell said...

This post is very interesting but the conclusion you seem to draw - that the negative results from this study mean that personality is not at least partly and possibly largely influenced by genetics - is not valid. All this study says is that common genetic variants do not have a large effect on personality. The GWAS study is not designed to assess rare variants, which are far more likely to affect protein function and thus affect the phenotype. The results are thus perfectly compatible with many personality traits being "hard-wired".

 
At August 09, 2010 6:35 AM, Blogger Sandy G said...

Well, I am one of the avid personality research watchers, so find your (and lehrer's) dismissal of personality traits a little unpalatable.
Increasingly personality traits are seen a spectrum traits and not as types or categorical constructs. similar is the thinking with regard to many traditional diseases like Autism and schizophrenia which are now seen as extremes on a continuum.
Genes, esp. SNPs' for complex diseases like Autism and Schizophrenia have been hard to find using GWAS; however other techniques like d-novo/rare CNV's are proving to be promising.
Perhaps SNP is more closely associated with types and CNV's with spectrum, but it is my understanding that heritabilities or genetic contribution (howsoever it is happening) cannot be dismissed so easily, esp if we assume that the underlying traits are on a continuum and thus be definition there would be only marginal effects of any genetic variation and not dichotomous type-related major effects.
I would thus be more circumspect before dimissing the entire personality construct as ill-found as Lehrer/Mischel have done. You dont seem to belong to that camp, but even the heritability (by whatsoever mechanism it manifests) may not be put to question by this study.

 
At August 09, 2010 10:40 AM, Anonymous Keith Grimaldi said...

@Neurocritic - I had seen the Risch meta-analysis and I think that Caspi has some fair points as well that it was a bit cherry picked. Also there are many other 5HTTLPR studies looking at other behavioral characteristics rather than depression. It may be more useful to look at endophenotypes which can be more rpecisely defined than endpoints like depression or particular personality traits.

The Zammit paper looks interesting, need to read it more carefully, thanks for the links.

Re the McClellan/King anti-GWAS paper mentioned above, there is a very good blog post describing why their argument is flawed over at GenomesUnzipped

 
At August 09, 2010 6:56 PM, Anonymous cornerstone university lansing said...

As I understand, genes do not have a direct effect in personality. “No genetic variants that significantly contribute to personality variation were identified, while our sample provides over 90% power to detect variants that explain only 1% of the trait variance. This indicates that individual common genetic variants of this size or greater do not contribute to personality trait variation”. I’m just wondering why some traits and behavior are said to be genetically inherited.

 
At August 09, 2010 10:40 PM, Anonymous Real Neurocritic said...

I'm not sure what Blogger did to Keith Grimaldi's latest comment at August 09, 2010 10:40 AM, but here it is:

@Neurocritic - I had seen the Risch meta-analysis and I think that Caspi has some fair points as well that it was a bit cherry picked. Also there are many other 5HTTLPR studies looking at other behavioral characteristics rather than depression. It may be more useful to look at endophenotypes which can be more rpecisely defined than endpoints like depression or particular personality traits.

The Zammit paper looks interesting, need to read it more carefully, thanks for the links.

Re the McClellan/King anti-GWAS paper mentioned above, there is a very good blog post describing why their argument is flawed over at GenomesUnzipped

 
At August 10, 2010 2:49 AM, Anonymous Keith Grimaldi said...

Thanks - I have had a similar problem on my own Blogger blog - some comments arrived in my mail box that did not get posted to the site, seems to be OK now

 
At August 10, 2010 10:15 AM, Anonymous KevinH said...

Interesting post that brings up a couple of thoughts.

First, I'm not that up on personality psych, so how do self-rating questionnaires correlate with objective or third party based tests?

Second, the statistical comparison seems doomed to fail. The huge number of SNPs relative to participants means that you are guaranteed to get a SNP that explains a large amount of variance, which means they must be doing some heavy correction to get have the highest variance explained be 0.5%. At that level of correction, even a true positive would be false.

There seems to be a lot of better statistical frameworks to use in this type of testing. Using the entire genome and then trying something like leave-one-out cross validation or permutation testing would give you an idea of how much variance is explained by the totality of the genes in a fairly unbiased way.

 
At August 10, 2010 7:18 PM, Blogger The Neurocritic said...

Kevin Mitchell - I stand by my conclusion: "So don't rush out and spend $1,397 on the Inborn Talent Genetic Test just yet..."

But seriously, you can't say the results are Good News for the Genetics of Personality. Ultimately I let the authors speak for themselves, since this is not my area of expertise. They clearly acknowledged the issue of missing heritability. But I think the idea of many personality traits being "hard-wired" is kind of silly, unless by "hard-wired" you mean 40-70% of the variance cannot be explained by genetics.

Sandy G - I'm not entirely nihilistic about personality traits. I just wanted to point out that some researchers take issue with Cloninger's temperament scales. And since the behavioral data were collected way back in 1988 and 1990, Verweij et al. used the old T/F version with fewer temperaments and no character traits.

 
At August 11, 2010 12:43 AM, Blogger Kevin Mitchell said...

I agree that spending any money on the currently popular genetic tests that give you a profile of common variants is a complete waste of money. I repeat however, that the results from this study have absolutely zero bearing on the general conclusion from twin studies that personality traits are highly heritable. The authors only found that these traits are not influenced by common genetic variants - differences in the DNA code at certain positions where some proportion of the population carries an "A", for example, and the rest have a "C", say.

Common variants are common because, for the most part, they don't do anything. They are effectively neutral and so are allowed to persist. Mutations that actually affect a protein's structure are the ones that cause a phenotypic change - these tend to be rare because they tend to be deleterious at some level.

So, we can expect the missing heritability to be found in these rare mutations which were not assessed by this study.

As for what contributes to the remaining variance, it is quite possible for a trait to be completely innate even if it is only partly under genetic control. Random variation in how the brain develops - even between individuals with an identical genotype - can lead to brains that are literally wired differently.

For more on this, see:

http://wiringthebrain.blogspot.com/2009/06/nature-nurture-and-noise.html

 
At August 11, 2010 6:41 AM, Blogger Eric said...

Just based on simple observation, I think there's a significant possibility that most personality traits develop in utero. There is still a strong genetic component at play, but the interaction of antigens and other environmental factors in a mother's womb can be very complex (ala Rh factor, genetically influenced but involving a complicated interplay of antigens). We already know that some personality components can be strongly influenced this way, for example, a mother who is nutritionally deficient at critical development point can have a male fetus develop as a girl, and that successive male children born to the same mother will have increasingly "feminized" traits (see the fraternal birth order studies). We also see these kind of adaptations in other species. Obviously there can be massive advantages to "real-time" personality tailoring, i.e., a child (or offspring in any species) developing to some degree based on environmental conditions as best as can be transmitted through the current condition of the mother, as opposed to the more static genetic constructs we usually think about. I think there's been very little research into this, and it's not surprising that the more conventional notions of how we expect personality to develop are going to be wrong.

 
At August 11, 2010 8:54 AM, Blogger petrossa said...

And this? http://www.frontiersin.org/people/colindeyoung/18541

My research focuses broadly on the structure and sources of personality, attempting to determine the relations among different personality traits and the neurobiological factors that influence personality

Points at genetic element.

 
At August 11, 2010 9:04 AM, Blogger petrossa said...

forgot link in last post:
http://www.tc.umn.edu/~cdeyoung/Pubs/DeYoung_2010_Big_Five_brain_structure_PS.pdf

 
At August 11, 2010 9:37 AM, Blogger SustainableFamilies said...

Eric I was about to say exactly what you said! But I'm so glad you said it because I had no scientific backing for my theory. However if the following were true;
A: Genes do not account for the larger portion of personality traits

and B: Twin and adoption studies find that siblings and biological relatives even raised apart from each other have eerily similar traits

Then isn't possible that:
There are other forces at play in the mechanisms of passing hereditary traits than only DNA/genes?

What if not only do the emotions and experiences that a mother is having while pregnant affect her biology and thus her offspring, but as trauma can affect in some manner the genes... (according to some recent research) what if even her PAST experiences can affect the DNA and also her biology and thus affect the child?

And I'm going to push this to a crazy level, but really in the field of science I think it's good to create theories and test them even when many would say "that's impossible"

So what if having a grandfather who had experienced x,y,z had put certain tags on the genes and they pop in in numerous further generations?

Further, rather than assuming that we need to give people some medicine to fix this "genetic problem" what if the genes are actually doing something that makes sense given the trigger that caused them to respond that way?

What if for example, extreme stress tags genes to make changes in order to adapt to the stressors?

What if there is more going on in evolution than simply completely random genetic mutation?

Ok... done rambling. : )

 
At August 11, 2010 1:07 PM, Anonymous LMK said...

I personally don't believe that this study is "bad news for the genetics of personality".

Before I start, let me give a disclaimer; I am not a geneticist and am a bit behind on the latest research on personality and temperament.

1) I agree with Farmer and Goldberg; Clonginer's theory of temperament is a flawed set of personalty constructs. Using a flawed set of constructs and trying to then do genetic testing based on those constructs is a recipe for failure. It would be interesting to see this study performed with other temperament scales.

2) Temperament and personality theories are based on traits. When we measure traits, we tend to label someone as "this, not that". But traits exist on a continuum. You tend to be more this than that. The best example IMO would be behavioral inhibition (BI) and extroversion (E). Twin studies show a strong genetic predisposition on the Extroversion scale. While I think we want to find a simple genetic indicator for E v BI, I doubt one single gene will be found that regulates E v BI.

This issue makes it incredibly difficult to study genetics and temperament. How exactly can we do reliable genetic research on traits that are measured on a continuum? Sure, we can easily round up a group of introverts, but amongst that sample, subjects will vary on their degree of behavioral inhibition.

3) Since one's personality is a compilation of one's temperament traits and how those traits are expressed, isn't it possible that several genes are responsible for the combination of traits that we see in individuals? Is it reasonable to try to isolate one trait and then try to isolate the genetics for that single trait when traits work together? I admit, genetics is not my area.

4) Kevin Mitchell states: "As for what contributes to the remaining variance, it is quite possible for a trait to be completely innate even if it is only partly under genetic control. Random variation in how the brain develops - even between individuals with an identical genotype - can lead to brains that are literally wired differently."

I absolutely agree.

The genetics of personality and temperament is going to take a very long time to tease apart. Temperament is simply too complicated for us to tease apart genetically at this point. Add to that other biological issues such as individual cortical organization and the issue becomes particularly difficult to tease apart. But to say that because we can't do so at this point based on one temperament theory really jumps the gun.

 
At August 11, 2010 1:40 PM, Blogger Eric said...

@SustainableFamilies Yes, there has been some evidence that there can be some adaptive encoding of DNA and genes. However, I don't know much about it, and don't myself know of anything that would suggest that this it has a significant ability to propagate useful genetic information to future generations.

I would be very careful about making any conjectures about this without first having observed such an event. Just creating a theory to test is backwards. What you want to do is to try to understand something that you observe. At that point, you can come up with testable hypotheses for it. But be assured - evolution is mostly not random genetic mutations.

I don't think this is what's going on in utero. I just think personality has a large contribution from factors in the womb, which can be affected by the external environment, and which can't be described by simple gene permutations. I'm surprised it's not already a field of research unto itself.

 
At August 12, 2010 3:05 PM, Blogger SustainableFamilies said...

I am equally surprised it's not a field of research unto itself. The reason it's such a deep issue for me does have to do with observing phenomena. As an adopted person, and as someone who face an unplanned pregnancy as a teen and was assured by "the experts" that adoption was the best solution, the field of how a person becomes who they are, and how best to serve people who are born to people who have mental health, emotional, or psychological issues is of deep relevance to me.

If infants were born as blank slates (absolutely untrue), and further infants had no knowledge of losing a mother in the first few months after birth (undetermined by research) then adoption would make the most sense.

However adoptees tend to display many of the same issues as their biological parents. Adoptees tend to have IQs that often match their adoptive parents until middle school when their IQs match their adoptive parents. Further more in talking about "IQ" there are a lot of other phenomena that are encompassed in that term; i.e. are you observing attention deficit that is impairing perfomance on IQ test, or you observing mood disorders that are affecting mental performance, are you observing allergic symptoms that are causing impaired brain functioning, chronic sleep impairment that is causing brain dysfunction? What exactly is the cause for the IQ switch and is it actually a shift in mental performance due to genes that relate directly to IQ or are there other forces at play?

Emotional natures as well may match the environment provided by adoptive parents until teen years when mood begins to match biological parents more closely.

The reason that this phenomenon occurs is fairly unknown and scientists like to equate it with genes becoming active.

But here's where I think it get's tricky. For example, my sister and I have the same issues even though we have only met two times in the 28 years we have both been alive. We share 50 percent of the same DNA. My cousins who also share roughly 50 percent of the same DNA have different issues. Obviously what my sister and I have that my cousins don't have is that we experienced the same womb, and we experienced being born to a woman who had the same external factors influence her genes over the course of her life until our births.

And further more, my sister and I have issues that mirror issues that mother had in response to events that happened to her. Those events did not happen to us.

And yet we seem to have many of the same symptoms of the events that brought out those symptoms in our mother. So what I mean to say is; if our mother had not incurred trauma that seemed to spark a number of somatic health problems in her that are unique to her and otherwise not found in the rest of our biological family, would she have past that set of symptoms to her offspring?

I recognize that the current theory would simply be that she had "the predisposition" in her genes and that those symptoms "would have happened no matter what" and she would have passed on the same set of symptoms to her offspring no matter what happened in her life.

However even if the mechanism that, for example, if a mother has experienced trauma that has caused biological symptoms of immune stress, exhaustion, and illness in her body and those biological processes affect the creation of the offspring in the womb, I also wonder if those stressors don't trigger DNA responses that can be passed on the offspring and be triggered in middle school ages.

So I would love to find any research that has been done in this area. I also wonder if, for example, a person who has incurred trauma that has affected them biologically can find some measure of healing, if that healing can in some way affect the well being of further offspring.

 
At August 18, 2010 5:28 PM, Blogger SustainableFamilies said...

HA!!!! THIS IS WHAT I"M TALKING ABOUT YO!

http://www.healthyalterego.com/index.php/2010/08/want-to-change-your-genes-just-change-your-mind-epigenetics-explained/

In case you were thinking I was way off base, there ya go! Granted I'm not knowledgeable enough to know how credible this is and a number of statements in that article are obvious intentional misrepresentations of the reality:

ie- "We control 95% of our gene expression" my ass. 95% may be influenced by environment, however we can't control nearly 95% of our environment even with every good intention.

 
At August 18, 2010 5:32 PM, Blogger SustainableFamilies said...

But seriously, my brilliance aside,(yes I did jump up and down and say 'I'm so right!!!' a few times LOL) what do you think about the validity of the article?

 
At August 29, 2010 2:46 AM, Blogger Tejaswini said...

really very interesting

 

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