It most probably starts as solely the former; but thanks to the wonder of Post-Decisional Dissonance, the latter can also play a role. You are unlikely to invest time and emotional energy into a relationship if you do not care for a person. However, once you have done so, you may value the relationship more than you would have predicted beforehand.
As Mark said, though, the nature of human relationships and their perceptions thereof is a very subjective and situational thing. I can quote Psychology Academics all day, but that's only one part of the equation. We're a long way from understanding and quantifying it.
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The Master said: "It is all in vain! I have never yet seen a man who can perceive his own faults and bring the charge home against himself."
>Analects: Book V, Chaper XXVI
As Mark said, though, the nature of human relationships and their perceptions thereof is a very subjective and situational thing. I can quote Psychology Academics all day, but that's only one part of the equation. We're a long way from understanding and quantifying it.
---
The Master said: "It is all in vain! I have never yet seen a man who can perceive his own faults and bring the charge home against himself."
>Analects: Book V, Chaper XXVI