I trust my own observations and my conclusion is that heritability is very strong. This is not a view that was imparted on me, quite the opposite. Growing up in a western country I was led to believe we are all blank slates, and I truly believed it. Once I started spending more time around the opposite sex some doubts started to emerge. Once I became a parent it became very apparent that this ideology had no basis in reality. Kids come with a personality, batteries included, and it's very easy to point out even individual behaviors that originate with either parent. Boys and girls are also very different on average. It's insane that we have somehow convinced ourselves that this is not the case, and I will surely be attacked by just pointing this out. I don't need twin studies to understand this basic fact, a fact that's been apparent to everyone throughout history, except for the past ~40 years in the west.