Thinking Causes Selfishness?

Perhaps.  If people stop to think, they are more likely to behave selfishly.

... humans are predisposed to cooperation and generosity, and only become selfish when they take time to think about the situation. The effect was robust, occurring both in subjects recruited from AMT and in college students.  Furthermore, a meta-analysis of previously published work showed that this effect was observed not only in the donation scenario described above, but also in other social “games” (such as the prisoners’ dilemma) that are either played just once or repeated multiple times.

The researchers were even able to manipulate participants into being either selfless or greedy, based on whether they were primed to think about intuition or careful reasoning.  Some participants were primed to believe in their intuition by asking them to either write an essay about a time in their life when their intuition was right, or when careful reasoning was wrong. A second group, which had to write about when their intuition led them astray or when careful reasoning proved helpful, was primed to promote rationality. When asked to contribute money, donations were much higher in the first, intuitively-primed group than in the second group, which had been primed for rationality and reflection.

Nod to MAG