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I have not spoken to my mother in 15 years but recently connected with her and her side of the family. I was primarily raised in a different sub-culture after the age of 4. As it turns out I "accidentally" have a lot in common with my maternal relatives. We like and dislike many of the same things. Is there some dominate trait in our nature which affects our psychology to cause us to agree on everything from TV, food and lifestyle?

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Certainly genetic and epigenetic effects could be underlying a tendency to have similar likes and dislikes. Essentially you are asking if behaviour and personality traits are heritable right?? –  GriffinEvo Oct 15 '13 at 8:37
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@caseyr547 Behaviour, though partly genetic, is highly influenced by epigenetic, environmental effects and hence cannot be attributed to genetic or environmental determinism perfectly. It has some genetic determinism, but it is much complicated by non-allelic interactions, polygenic effects, and also "non-mendelian" allelic interactions, hence is usually not simply dominant or recessive. –  Satwik Pasani Oct 15 '13 at 10:43
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@SatwikPasani makes a good summarization, and the same could be said of most traits, phenotype = genotype + environment –  GriffinEvo Oct 15 '13 at 11:47
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It's also surprising how much your tastes and personality can be set by the time you're four. We may not remember much from the time before then but those years are hugely formative. –  Amory Oct 15 '13 at 12:25
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All of the other comments are sure true, but you should also consider confirmation bias. You have been reunited with someone after a long time and probably the things you have in common surprise you more than those that you have not in common (which you tend to forget). You should ask someone else (best would be a stranger) to take, say, 50 different "characteristics" (e.g. "like cinnamon in cake", "like skying" etc.), then count how many you have in common with your mother. Then repeat the same exact count with someone who is unrelated to you. –  nico Oct 16 '13 at 6:47
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closed as too broad by terdon, Amory, jonsca, fileunderwater, von Mises Oct 28 '13 at 16:31

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1 Answer

In this answer I mainly repeat the comments!

There are several reasons why you might share some traits with your mother.

  • genetic (see below)
  • epigenetic
  • environmental influence while being in the womb
  • environmental influence up to the time you were 4 years old
  • the two environment were not so different (maybe because your adoptive parents wanted to follow the will of your mother or just because by chance your adoptive parents have similar behaviour that your mother)
  • multiple testing issue (see below)

These reasons can be classified into three categories:

  • environmental variance
  • genetic variance
  • poor observation (statistic mistake)

The phenotypic variance in a population is influenced by the environmental variance + the genetic variance + the variance due to the interactions between the environmental and genetic variances. The heritability can be calculated as the part of the phenotypic variance which are genetically determined. Such calculations make sense only for populations not for a given parent-offpsring pair.

genetic: It does not make sense to ask whether the variance of a trait is dominant or recessive. It makes sense to say that "liking pink" is dominant over "liking blue". Therefore, you should tell us what is the variant of a given trait that you share with your mother. In such case we might tell you if this variant is dominant or not over the other variants. But of course, this works only for traits that are at least slightly genetically determined. liking a color will certainly not have a strong genetic variance for example. And even if a trait is 100% genetically determined, complex genetic architecture might make it hard to answer. For example a given variant might be dominant in a given genetic background but recessive in another. Finally, I should say that it costs to perform the necessary study (Genome Wide Association Studies) to know exactly the part of the variance of a given trait that is genetically determined. And of course, such studies depend on the population we look at.

Multiple testing issue: Without realizing, you actually looked at many different traits. You might have looked at your favorite color, your favorite beer, the way you wash your teeth, the sport you practice, the color of room, whether you are calm or impulsive, etc... You might not have paid attention only to things that match but you would have found as many similarities (not the same ones though) with any other human on earth.

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