The Basics of Human Compatibility

We all have many potential romantic partners and there are many factors that we use to find the right person – both consciously and unconsciously.

Scientific research has shown that relationship markers – a combination of genetics and psychology – strongly affect who we are attracted to and how successful our relationships are.


Genetic Compatibility

For well over a century now, genetics has been used to understand the physical compatibility between people. One well-known example of this is organ transplantation.  For an organ transplant to be successful, the recipient’s body must accept it indefinitely.  Medications benefit this process, but multiple other tests help maximize the compatibility between donor and recipient.  These tests include genetic testing of the donor’s and recipient’s immune system genes.  The more similar the immune system is between donor and recipient, the more likely the organ transplant will be successful.


Biological Compatibility

Biological compatibility is another form of genetic compatibility between people. Couples in long-term relationships were often found to have very different immune system genes from their partner1,2,3,4. Research shows that children born to couples with very different immune system genes are more likely to successfully defend themselves against a greater variety of infections5. But not only does scientific evidence point to children with strong immune systems, the research has shown that these couples also enjoy more satisfying sex lives6, greater marital stability1,6, increased fertility rates7,8, and find each other more attractive1.


The Human Leukocyte Antigen System

Some of the genes in your immune system that will be classified in the Instant Chemistry process belong to the Human Leukocyte Antigen (HLA) system.  They are located in a genetic region of chromosome #6, known as the Major Histocompatibility Complex.  Although the HLA system is made up of many different genes, the three genes: HLA-A, HLA-B and HLA-DRB1 play an important role in biological compatibility9.  These genes help identify foreign entities in our bodies, such as bacteria causing infections. These genes also contribute to creating our unique body scent9. Research shows that we subconsciously detect how similar or different another person’s immune system is from our own through their body scent10,11. These instinctual preferences strongly affect human sexual attraction and help us chose our romantic partners.


Serotonin Transporter Gene

The serotonin transporter gene moderates the association between negative and positive emotional behavior and changes in marital satisfaction over time12. For individuals with two ‘short’ versions  of the transporter, higher negative and lower positive emotional behavior at the beginning of a marriage can predict declines in marital satisfaction over time. Instant Chemistry helps uncover this component of compatibility and empower individuals with ways to work with their results.


Psychological Compatibility

Four key relationship factors have been found to influence the success of a relationship:

Social Behavior—This factor assesses whether you seek out togetherness or prefer solitude, whether you prefer to be in the background or foreground of social interaction. In essence, are you most comfortable among people, or do you prefer your own company?

Dominant Behavior—The Dominant element consists of holding strong opinions, lower tolerance for differences in opinion, as well as lower tolerance for goal differences and need for control.

Submissive Behavior—The submissive element consists of a tendency to compromise, agreeable- ness, positive attitude, selflessness and acceptance.

Intimate Behavior—This factor assesses the extent of your preference for expressions of affection and whether you are prone to be open and revealing or more inclined to guarding your privacy.



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  10. Milinski, M, et al. Major Histocompatibility Complex peptide ligands as olfactory cues in human body odour assessment. Proc Biol Sci 280(1755) (2013)
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  12. Haase, C. et al. The 5-HTTLPR Polymorphism in the Serotonin Transporter Gene moderates the association between emotional behavior and changes in marital satisfaction over time. Emotion 13(6) (2013) 1068-1079