The Psychology of Existential Risk: Moral Judgments about Human Extinction

Written by Stefan Schubert



Do laypeople share the intuition that human extinction is much worse than near-extinction? In a famous passage in Reasons and Persons, Derek Parfit predicted that they would not. Parfit invited the reader to consider three outcomes:

1) Peace
2) A nuclear war that kills 99% of the world’s existing population.
3) A nuclear war that kills 100%.

In Parfit’s view, 3) is the worst outcome, and 1) is the best outcome. The interesting part concerns the relative differences, in terms of badness, between the three outcomes. Parfit thought that the difference between 2) and 3) is greater than the difference between 1) and 2), because of the unique badness of extinction. But he also predicted that most people would disagree with him, and instead find the difference between 1) and 2) greater.

Parfit’s hypothesis is often cited and discussed, but it hasn’t previously been tested. My colleagues Lucius Caviola and Nadira Faber and I recently undertook such testing. A preliminary study showed that most people judge human extinction to be very bad, and think that governments should invest resources to prevent it. We then turned to Parfit’s question whether they find it uniquely bad even compared to near-extinction catastrophes. We used a slightly amended version of Parfit’s thought-experiment, to remove potential confounders:

A) There is no catastrophe.
B) There is a catastrophe that immediately kills 80% of the world’s population.
C) There is a catastrophe that immediately kills 100% of the world’s population.

A large majority found the difference, in terms of badness, between A) and B) to be greater than the difference between B) and C). Thus, Parfit’s hypothesis was confirmed.

However, we also found that this judgment wasn’t particularly stable. Some participants were told, after having read about the three outcomes, that they should remember to consider their respective long-term consequences. They were reminded that it is possible to recover from a catastrophe killing 80%, but not from a catastrophe killing everyone. This mere reminder made a significantly larger number of participants find the difference between B) and C) the greater one. And still greater numbers (a clear majority) found the difference between B) and C) the greater one when the descriptions specified that the future would be extraordinarily long and good if humanity survived.

Our interpretation is that when confronted with Parfit’s question, people by default focus on the immediate harm associated with the three outcomes. Since the difference between A) and B) is greater than the difference between B) and C) in terms of immediate harm, they judge that the former difference is greater in terms of badness as well. But even relatively minor tweaks can make more people focus on the long-term consequences of the outcomes, instead of the immediate harm. And those long-term consequences become the key consideration for most people, under the hypothesis that the future will be extraordinarily long and good.

A conclusion from our studies is thus that laypeople’s views on the badness of extinction may be relatively unstable. Though such effects of relatively minor tweaks and re-framings are ubiquitous in psychology, they may be especially large when it comes to questions about human extinction and the long-term future. That may partly be because of the intrinsic difficulty of those questions, and partly because most people haven’t thought a lot about them previously.

In spite of the increased focus on existential risk and the long-term future, there has been relatively little research on how people think about those questions. There are several reasons why such research could be valuable. For instance, it might allow us to get a better sense of how much people will want to invest in safe-guarding our long-term future. It might also inform us of potential biases to correct for.

The specific issues which deserve more attention include people’s empirical estimates of whether humanity will survive and what will happen if we do, as well as their moral judgments about how valuable different possible futures (e.g., involving different population sizes and levels of well-being) would be. Another important issue is whether we think about the long term future with another frame of mind because of the great “psychological distance” (cf. Trope and Lieberman, 2010). We expect the psychology of longtermism and existential risk to be a growing field in the coming years.

** Equal contribution.

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One Response to The Psychology of Existential Risk: Moral Judgments about Human Extinction

  • Carl Oguss says:

    There are seven stages of moral thinking that have been identified by developmental psychologists, although persons at stages six and seven are few and far between. In stages one through six, inclusive, the highest moral value is that desireable outcomes be applied to every growing proportions of the human race and at stage six we are seen as benevolent gardeners of the planet who also care for and about many other species. Ir is an increasingly broad web of caring about others that defines the progression through the stages and levels of morality, the latter being first preconvention, then conventional, and thereafter post-conventional.
    However, at stage seven people finally outgrow “species bias” and no longer give primary value to the existence and development of the human race. It is at stage seven that we see that we are a cancer on this planet, and we are likely to want to expand our domination of all places and living things in whatever ways best suit our interests, just as if other living species were our property or we had a moral right to rule over every place we might go, outer space included. At stage seven this moral bias is cast away and the conclusion often is that the rest of all of the lifeforms on the planet would be much better off if we all became extinct. However, this is not always the case and just as with all of the stages there are no single agreed-upon conclusions that define the stage, only depths of perception and caring.
    In this case, other stage seven persons might look at the natural tendency to have CO2 become trapped in the tiny shells of ocean species and see that this process would eventually remove so much CO2 that all plant life and therefore all life would cease to exist; this is at least true for larger lifeforms; whether it is true of all lifeforms (e.g., viruses and bacteria) is another question.
    If a stage seven person believes that only humans can save the rest of the larger lifeforms from ultimate extinction, then they would justify some of us existing and producing the much-needed CO2, likely also hoping we would become uniformly enlightened gardeners of a green planet.

    Carl Oguss
    Hawaii Dog Psychology Center