<aside> 💡 This is one of the #UnprofessionalScientificStories I write. I turn my psychology learning into stories because I want to communicate science better to the general audience. Due to the storyline and my insufficient scientific knowledge, some descriptions might not be accurate. I will continue practicing and improving. Thank you for reading it.

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When she heard that H was cheating on his girlfriend because he had feelings for many girls, she wasn't surprised. She has learned species could be prone to monogamous relationships and polygamous relationships, but humans weren't typical for either of them.

She knew that for species with monogamous relationships, pair-bolded species, males have more extensive parenting behavior and have smaller testes size, lower sperm count. Some birds will even feed females with worms during courtship to demonstrate they could be a good daddy.

On the other hand, for species with polygamous relationships, tournaments species, males didn't take care of their children but only contribute genes. They need to show females that they have better secondary sexual characteristics(e.g., big muscles) to prove that they have better genes.

As far as she knew, humans were kinda in the middle. That's why she was calm when H told her he couldn't control himself. It was expected, but cheating was still wrong.

H claimed, "I know I am cheating, but if my girlfriend didn't know, she would never get hurt. I love her. I don't want to hurt her." Piece of bullshit, she thought. It already happened.

"What we perceive is the reality," H added as if he could read her disapproval. She sighed. She felt something was wrong, but she couldn't identify it. She recalled that H was one of the outstanding debaters when he was back in high school.

"People won't think like this if they find out," she said. She assumed when H explained himself, vmPFC activated. He was reflecting on different emotions. Yet, others were different. If they heard the same story, insula and dlPFC would activate. It would evoke anger and disgust, and ruin his reputation.

He didn't listen. Three months after, gossips about H cheating spread in every corner of their school. Rumor said that H argued with his girlfriend, "Yes. I cheated. But if I still love you, I would still marry you. What's the big deal?"

She didn't contact H to talk about it, nor agreed with the rumors. People would justify themselves anyway. For her, morality was just self-serving. At least, she believed it was humans' biological nature.