Psychopathy and Evolutionarily Stable Strategies
If you were asked to list evolutionary adaptations that make successful people successful, chances are that psychopathy is not what springs to mind. However, psychopathy is a trait that allows individuals to exploit others to give themselves an advantage. This means that if someone else is a non-psychopath, it can be advantageous if you are a psychopath so you can take advantage of them without feeling guilt (disclaimer: I am not advocating taking advantage of other people; I simply aim to argue that it has some evolutionary merit). As a note, when I talk about mixed strategies, I am referring to mixed strategies at the population level rather than at an individual level.
Fortunately, although taking advantage of people may at first seem like it will always outcompete every other strategy, it in practice will not. In particular, the first article discusses cheating, a behavior towards which psychopaths are particularly inclined, and how it results in a mixed-strategy equilibrium. Cheating can raise reproductive success since it allows the individual to get with multiple partners (this is particularly true for males). However, if too many people cheat, then the cheating behavior becomes less beneficial because there are not enough people to take advantage of and so it remains fairly low in the population (according to the article). Thus we get an evolutionarily stable mixed equilibrium with a low proportion of cheaters (often psychopaths) and a high proportion of non-cheaters.
Another explanation explored in the Mealy paper is that although people who are higher in Machiavellianism (e.g. psychopaths) can outperform other people in making rational decisions when there isn’t as much of a payoff for cooperating, they are less successful than other people in situations where long-term cooperative relationships can be formed (the paper references multiple studies giving experimental data for this). Thus the particular game being played affects the payoffs for being a psychopath. Additionally, for an example of psychopaths not being the optimal strategy against each other, the paper makes the conjecture that psychopaths would be worse at judging the other person and so when paired together to play with each other would perform worse in iterated games. This can help to explain why we have an evolutionarily stable mixed strategy with a low but stable number of psychopaths in a population of mostly non-psychopaths.
This observed phenomenon shows a striking similarity to the Hawk-Dove game that we studied in class. In that game, the payoffs are such that neither strategy is a best response to itself, and so we end up with an Evolutionarily Stable Mixed Strategy. That is similar to psychopaths and non-psychopaths; if the other person is not a psychopath, it is often desirable to be a psychopath so you can take advantage of them; however, if you are both psychopaths, then you would both be expending effort trying to take advantage of each other and so it is not a best response to itself (it could be conceivable that in this case it is better to respond as a non-psychopath to a psychopath instead, depending on the situation). This means that the Hawk-Dove game is surprisingly well-reflected in real-world phenomena such as psychopathy.
In short, we have an evolutionarily stable mixed-strategy equilibrium for psychopaths and non-psychopaths, but fortunately for you the percentage of psychopaths is quite low.
Sources:
https://www.zmescience.com/science/difference-between-psychopath-and-sociopath/
https://www.cambridge.org/core/journals/behavioral-and-brain-sciences/article/abs/sociobiology-of-sociopathy-an-integrated-evolutionary-model/A5F1DDC8F0D32E036B725FE7BFA761AF (download the pdf, article starts on page 121 of pdf, which is numbered in the journal as page 523)