I agree with Analogy’s take on this. I don’t think it’s based on ‘needs’. Selfish people are, and have always been selfish regardless of the situation. Stress does exacerbate it of course. And it’s unfortunately the case that we live in a world that doesn’t reward kindness. But despite this there are a lot of people that are kind because they want to be, because it’s rewarding for it’s own sake.