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The Psychology Query - Number 3: Heredity of Personality, Twin and Adoption Studies

Updated on May 8, 2017
Natalie Frank profile image

Natalie Frank, a Ph.D in clinical psychology, specializes in pediatrics, health psychology, and behavioral medicine.

This issue has to do with temperament and how much of temperament is inherited. I’d like to point out a few things that came to mind before we begin, as it touches on the question and the way the question is asked.

The first thing I’d like to underscore is the importance of understanding that using negative labels for others as well as ourselves can lead to harmful self-fulfilling prophecies. When we insist on first labeling someone and then treating them as if that label is accurate, even despite all evidence to the contrary, they will come to see that nothing they do will affect a change in the other person’s attitude. If this is the case, they have no need to try to be anything other than exactly what they are being called, coming to believe it is true. Honestly, this is a form of emotional abuse.

The same thing happens when we label ourselves. Most often, this tendency develops as the result of others labeling us for long periods of time, often from the time we are children. We may reach a point when we begin to internalize these labels and messages, taking over where others have left off or adding insult to injury by joining them through self- abuse. The harm this can do is enormous.

Another thing that struck me this week is the way the reader asks the question. It seems that there is a Catch-22 that is suggested, one that many of us may find ourselves in. The question for today comes from a reader who wants to know about introversions and shyness, suggesting that extroversion is the desirable option while their introverted nature is problematic. They also show a tendency than many of us have which influences our own self-concept or someone else’s. First they seem to believe that they must have done something wrong to end up changing something positive that they must have naturally inherited to something negative. Immediately afterwards, they imply that they believe what they view as negative cannot be altered because it was inherited.

I’m sure many of you can see the logical flaws here. Everything is skewed to imply something negative about the reader. On the one hand it is their “fault” that they have this “negative” personality. Both parents are extroverted so they must have inherited an extroverted personality from them. Yet they know they are introverted so they must have done something, the assumption is something bad, to cause this change. At the same time they are assuming, since they believe that personality is inherited, they can’t change it back. Yet the natural assumption would be that what they inherited was extroversion not introversion.

This type of thinking is no stranger to many of us. The assumption that it is their “fault” they have this “undesirable” personality, while also assuming they will always have this personality is a type of attributional style that can lead to depression. This way of thinking is something that is characteristic of many of us. It is believing that bad things are our fault and we have no control over them, can never change them. Once we alter this way of thinking about things we come to understand that there are always other options in terms of how we view things and for affecting change in our lives. But this is a topic for another post. The major point here is that personality is not good or bad.

There are a lot of things that can be said here but I just want to note a couple. First, let me repeat that personality characteristics are neither good nor bad. They are neutral. They can play out in a positive or negative way depending on the situation and how they are applied. Second, patterns of inheritance and personality are both extremely complex things. Personality is made up of many different characteristics. The potential inheritance of factors that may lead to the development of certain personality traits is not a direct path and the environment has a lot to do with shaping our personalities as they are developing.

Instead of viewing certain opposite characteristics as all positive or all negative, we can do a lot more good by trying to see how both can be positive. Examining how our strengths can be used to help us better adapt certain qualities to more situations can enhance our flexibility. Extroversion is not automatically good and introversion is not automatically bad.

I have heard individuals insist that others who are introverted have “no personality.” This is sheer idiocy as there is no such thing as a person who has no personality and someone who needs to see all of their own characteristics as good and anything different as bad is closed minded and lacking in self-esteem. The fact is there are a range of personalities, characteristics, perspectives, opinions and interests is what makes the world interesting.

If you find yourself labeling others negatively, look into the reasons why. Negative labeling is often a defense. It is sleight of hand to deflect attention away from something a person feels is a weakness in themselves, a smoke screen to hide something lacking in their own life at another’s expense. Instead of doing something that causes someone else harm, determining how to focus internally to take care of what is believed to be lacking or missing, is a far healthier approach.

And now back to our regularly scheduled programming.

Answers to Reader's Question

Question: How can you tell if something is inherited or not? I have seen twin studies and adoption studies and don’t understand why both are used or what they can show about inheritance patterns. I am curious because I am extremely introverted and shy, while both my parents are extroverted and outgoing. I thought personality was inherited. Could I have done something to change my personality from the way I would have inherited it, to one that’s undesirable? If personality is inherited is my introversion permanent so there’s nothing I can do about it?

I hope you have read my intro and understand that introversion is not automatically bad and extroversion is not automatically good and don’t let anyone tell you otherwise. Also, remember that introversion/extroversion represent a single quality, a trait not a “type” of personality.

You and your personality are so much larger than that single characteristic. Your personality is multifaceted and complex as is everyone’s. Each characteristic has both positive and negative aspects depending on the situation and others you are interacting with. Sometimes it may seem that you are not as “social” as others or that you don’t value social interaction and relationships as much as others do. This is a falsehood. Needing “space” doesn’t mean you don’t value social time. You just need more private time to recharge your batteries after a lot social interaction.

Introverts also tend to be highly sensitive and feel things deeply so you likely value relationship just as much as, if not more than, your fellow extroverts. Of course, this is a generalization. However, being introverted does not mean you don’t care about others or want to build strong relationships just as much as others you know who are extroverted.

I am also an introvert and a great book I highly recommend is “Quiet: The Power of Introverts in a World That Can't Stop Talking” by Susan Cain. This book really struck a number of chords with me and presents introversion in a different, more positive, light. It explains how the characteristics of introverts have enabled them to make many great contributions to society now and in the past. You'll come away with a whole new understanding of the strengths of those who are introverts..

A Wonderful Book Explaining How Introverts are Special

I believe that the reason there are different people with different personalities is that each a unique way of helping them cope with whatever life throws their way both good and bad. Different ways of coping may be better for certain situations. The fact that there are many different personality traits and coping techniques out there means each of us needs others and are needed in return. We all have the ability to help others when they aren’t sure how best to handle a tough situation. Likewise, when we are in a tough situation, there are others who have the capacity to help us view things or deal with them in a different way.

Never think that because you are introverted you do not have crucial contributions to make to others around you and to the world in which you live. You don’t have to change your personality to make this a reality, it already is one. Let others see what you have to give and surround yourself with those who appreciate you for who are and who you appreciate and can grow from being around in turn.

That being said, onto your question. Actually, it is temperamental qualities that are said to be inborn or influenced strongly by heritability or the degree to which it is inherited, and less so by environment. A brief word on terminology here. Inherited means that certain traits are passed on by our biological parents. Something that is genetic may or may not be inherited. Sometimes birth defects may be caused by genetic mutations that have nothing to do with inheritance. A disorder may therefore be genetic when it spontaneously develops in the child without either parent having it or being a carrier.

Researchers believe we come into the world hard wired for certain things including temperament. Temperament is believed to be extremely difficult to alter. This is thought to have a high heritability though not at the individual level (see below). Temperamental qualities are said to be the building blocks for personality but personality is also strongly influenced by environment.

Heritability is more formally defined as the extent to which genetic individual differences among people in a population contribute to individual differences in observed behavior. What is not caused by heritability is said to be caused by the environment or any non-genotypic influences. Note however, that heritability and environment are population concepts. They do not describe anything about an individual. If the heritability of shyness is said to be .40 or 40% all that tells us is that, on average, about 40% of the individual differences that we observe in shyness in a population may be attributable to genetic individual difference. It does not mean that 40% of any individual’s shyness is due to his/her genes while the other 60% is due to his/her environment. In other words, within a population you have a range of shyness from extremely shy to extremely outgoing. Heritability is the degree to which the genetic differences found in the population predicts the range of shyness found in the population.

The two designs most frequently used to determine genetic and environmental influences on infant and child temperament are twin studies and adoption studies. Twin studies compare monozygotic twins who are genetically identical (MZ) twins with dizygotic orr fraternal (DZ) twins who share approximately 50% of their genetic makeup and are no more similar than other biological siblings. When similarities in a characteristic is greater for MZ twins than DZ twins this suggests a genetic influence. When the opposite is true a stronger environmental influence is suggested. Because MZ twins are genetically identical differences between them can only be due to environmental influences that are unique to each individual or aren’t shared. Studying twins reared apart and together give an even clearer picture of these influences.

Adoptive/nonadoptive sibling studies are based on similar logic, but compares the similarity of adoptive and nonadoptive sibling pairs. In these studies, a genetic influence is suggested for a characteristic when biological siblings who share about 50% of their genes, are more similar on that characteristic than adoptive siblings who share none of their genetic makeup. Shared environmental influences are suggested when genetically unrelated adoptive siblings resemble each other on the characteristic.

All this goes to say that temperamental factors such as mood, persistence, approach/withdrawal or comfort with strangers or unfamiliar situations, adaptability or the ease of transitioning, are factors which predict later personality characteristics such as introversion extroversion. Yet this may occur through other factors. For example, temperamental qualities such as low adaptability or withdrawal may lead to anxiety in situations that call for quick or frequent transitions or being placed in unfamiliar situations often. The anxiety which will act on these temperamental qualities, more likely leading to introversion than extroversion.

If however, the parents are aware of the difficulty they may help teach the child coping strategies for handling he anxiety such that though the child still would prefer more time to transition and familiar situations they aren’t upset or anxious when not provided with these. In this case the child will likely be less introverted. There may even be cases where a parent teaches the child to act in a way that is opposite of their natural tendencies in an effort to cope. These children may start off with characteristics normally more predictive of introversion but may end up become somewhat extroverted.

This is an extremely complex topic so I hope this helped explain your question.

Book Review: Raising Your Spirited Child, Third Edition: A Guide for Parents Whose Child Is More Intense, Sensitive, Perceptive, Persistent, and Energetic by Mary Sheedy Kurcinka

The spirited child, sometimes referred to as "difficult" or "strong willed," is a child who is temperamentally hard wired to be intense, sensitive, perceptive, persistent and uncomfortable with change. While many of these characteristics are thought of positively in adults, it can be hard to parent a child who shows these qualities. It is also easy to inadvertently negatively label these children, a tendency which can influence the child to become even more spirited rather than less.

This newly revised third edition of the award-winning classic was written by a Doctor of Education who has taught classes using these techniques. She developed this program when parenting her own spirited child. Whereas other approaches focus on disciplinary methods and rule setting to get the child to “behave,” without addressing the needs of the child, this book uses a strength based approach, showing how to use the techniques with real-life situations.

At the same time, the book helps you guide your child in learning how to address their own preferences and needs while using self-regulation techniques to maintain socially acceptable behavior. The author also provides exercises to help you understand how your child feels. This will enable you to take their perspective when helping them become more adaptable in response to the unpredictable aspects of their world.

Updates such as charts and quick tips make this edition even easier to understand. Examples provided by parents who used these techniques allow for a real life view of how to use the strategies presented. The book provides practical suggestions in a number of areas including:

  • How to manage both your own and your child’s intensity levels—not just the spirited child's, but yours too
  • How to achieve peaceful bedtimes, mealtimes, holidays, and many other commonly challenging situations involving breaking familiar routines
  • Using your child's strengths to overcome their difficulties
  • Teaching your child how to be a problem solver and how to cooperate with others
  • Updated guidance on establishing clear limits

This is a great book for both parents and children which provides a balanced focused on the needs of all members of the family as opposed to just making the child easier for parents to deal with. The results a happy family who enjoy being together and can adjust to tolerate differences and a well-adjusted child able to navigate adulthood to create a positive life.

If you enjoyed reading this, take a look at the first two issues below.

© 2017 Natalie Frank


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