This is an interesting question; a question that anyone with multiple children has grappled with. How can my children so instinctively respond just like me or my spouse? But on the other hand, how can two children from the same parents be so different?
One set of anecdotal observations says personality must be genetic – the level of commonality seems too great to be explained solely by environmental influence. But another set of anecdotal observations seems to say the opposite – if two children share so much genetic code in common, how could their personalities take on such contrasts?
In a recent sent of lectures I was listening to from a leading neuro-psychologist, he said that research estimates that 50% of the extroversion-introversion personality trait was determined by genetics. The other 50% was determined by factors such as home stability, birth order, early socialization experiences, etc…
On face value that’s not shocking. In the age-old nature vs. nurture debate that is about what we would expect; half of our personality is inherited, the other half is learned or molded. But it was the next two statistics that he gave from the same research that caused me to pause.
According to the research he reviewed, he said that:
- 60% of whether you are politically conservative or liberal was genetically determined and
- 70% of whether you marry and the quality of your marriage was genetically determined.
A quick word about his research; from what I could tell, his scientific work was excellent. He referenced meta-analysis studies not single study published research findings. There is a big difference in the quality between the two. Meta-analysis (in layman’s terms) average out the findings of hundreds of studies on a subject. A single published study is trying to find something interesting/significant enough to get published.
All of this to say, I am not questioning the quality of his work. To whatever degree that the hereditability of personality traits or life outcomes can be predicted scientifically, I trust the style of work Dr. Leary was doing. In addition to this, he is highly esteemed by his peers (not just popular media outlets, who tend to prefer the more eye-catching, yet-to-be-verified studies).
So what do we make of the 50% genetically determined personality statistic now? I think most of us would say it’s less impressive that we thought when we read it initially.
For the moment let’s assume all of the statistics are correct (I do not have the credentials or expertise to debate his methods). Let me frame two questions that help us assess what we do with the 50% hereditability of personality statistics.
- How much weight do you give the 40% of non-genetic factors in your political leanings?
- How much weight do you give the 30% non-genetic factors in the quality of your marriage?
My guess is most readers would say, “A great deal of weight.” As a hard-working father, I probably only get to share 30% of the waking hours with my two boys. But I believe those hours carry as much weigh/influence as (probably more than) almost anything else in their life.
I believe, if these numbers are true, we should think the same way about the choice-factors in our personality. If God knit us together in our mother’s womb (Ps. 139:13) and has plans for us to accomplish for his glory (Eph. 2:1), then why would be surprised that God began preparing us for those good works genetically from the moment of our conception.
As an important side note on this subject, I believe we must be careful not to place a good-bad distinction on the extrovert-introvert spectrum (or any other personality variable for that matter). Thinking of certain personality traits as good-bad, leads us to accept a can-can’t mentality on the basis of personality.
As a quick personal example, I am a pretty intense introvert. For a long time I assumed this meant I could not be a leader, public speaker, or (at times) even a good Christian husband. I mistook this personality trait for a limitation on my other gifts and abilities. Similarly, I mistook a relational role (leader) for a personality type (extrovert). Now I am comfortable being an introverted leader and husband.
So what should our take away from this reflection be? I would propose it should be the following three points:
- If 50% of my personality is genetic… (I can trust that God designed these elements of my personality to coincide with His purposed for my life),
- … then there is still 50% of my personality over which I have influence… (I should expect that I will frequently be called by God to do things that are uncomfortable to my natural bent and trust Him to give me whatever I need to accomplish these tasks),
- AND 100% of my personality can express itself in whatever ways necessary to accomplish whatever God lays out for my life.
Join the Conversation
How does viewing genetic influences in light of God’s design change the way you think about genetic influence upon personality?
How might the church reinforce the cultural notion (implicitly or explicitly) that certain personality traits are more valuable or desirable than others and, thereby, discourage a significant percentage of congregants?
Note: This post was originally posted on the “Grace and Truth” blog of the Biblical Counseling Coalition.
 The lectures were from The Great Courses series (www.thegreatcourses.com). The lecture series was “Understanding the Mysteries of Human Behavior” by Dr. Mark Leary, Garonzik Family Professor of Psychology and Neuroscience at Duke University. My reasons for listening these lectures were two fold. First, I wanted to be more informed of neuro-psychology. Second, my church has a large number of students from Duke University and I believed it was an important part of learning the community in which I serve as Pastor of Counseling.
 These statistics come from Lecture 3 “Where Do People’s Personalities Come From?” While I disagree with Dr. Leary’s predominant evolutionary beliefs about human origins and the development of personality, I do not believe these beliefs contrasts influenced his interpretation of this research.