• Humans might prefer bad events giving way to good outcomes over good events giving way to bad outcomes, holding net welfare constant. 
  • If this preference reflects a valid moral intuition that applies to both humans and non-human animals, then painful events at the end of life deserve additional moral weight because there is no scope for a better future. 
  • It would follow that improving the humaneness of the transport and slaughter of farmed animals is more urgent than the duration and severity of pain they cause would imply. 
  • There are at least two plausible explanations for why humans would value the temporal order of valenced experiences even if it had no intrinsic moral value:
    • People might implicitly assume that improvements in welfare result in greater total welfare because pain relief is itself rewarding (and, as such, might produce more pleasure than is initially apparent).  
    • Human compassion likely evolved to be sensitive to sudden need, not absolute need
  • Unless future research indicates that farmed animals themselves intrinsically value the trajectory of welfare, it is not clear that the welfare issues posed by transport and slaughter deserve additional attention in virtue of their occurence at the end of life. 

Epistemic Status

This report was the product of about three weeks of research, and as such may overlook relevant research or philosophical considerations that we did not find or have time to consider. Before finalizing the report, we spent about a week's worth of work revising it in light of new comments, but did not add any new sections. 


This report is a postscript to "The Relative Importance of the Severity and Duration of Pain", which was intended to contextualize cause prioritization decisions when sources of suffering they seek to ameliorate differ in duration and severity. The present report addresses an issue that has elicited some discussion in the philosophical literature, but to our knowledge has only recently surfaced in animal ethics: Does the temporal ordering of positive and negative valence states matter beyond its influence on the total amount of pleasure and pain experienced? 

Browning and Veit (20202022) say "yes." Their main premise is that end-of-life welfare is particularly important: "even when two lives contain an equal total sum of positive and negative experiences, it is still worse to have suffering at the end of life" (2022, p. 9). Therefore, the transport and slaughter of farmed animals deserve special consideration over and above the duration and severity of suffering they cause.  The following provides an exposition and evaluation of Browning and Veit's argument that the temporal ordering of suffering is morally relevant. To make the implications of their view clear, we contrast it with a simple hedonistic approach in which all that matters morally is the severity and duration of pain and pleasure. That said, none of our arguments against the moral relevance of the trajectory of valenced experience depend on accepting hedonism.

Shape of a Life

On a simple hedonistic approach to welfare, the temporal ordering of events per se has no intrinsic importance (de Lazari-Radek & Singer, 2014, Chapter 5, section 3). Timing only matters to the extent it affects future welfare. Browning and Veit (2020, p. 7) give an example of previously higher living standards making current low living standards seem even worse:  

enclosure space is an important determinant of welfare for captive animals. It is likely to be worse for an animal to have the positive experience of a larger enclosure space before the negative experience of a smaller one, because the perceived decrease in quality will add to the negative feelings brought about by the change. Conversely, moving from a smaller to a larger space will create additional positive feelings about the improvement. 

If the trajectory of welfare matters only instrumentally, then there is a case for preferring good welfare up until a bad death rather than the converse. As Browning and Veit (2022) acknowledge, "there may be some welfare benefits in having negative experiences concentrated at the end of life: if we take part of the harm of suffering as being in the ongoing effects, such as the memories of the experience. Suffering at the end of life is more temporary in this sense, and does not allow time for the animal to form memories that may cause more suffering in the future" (p. 9).

However, Browning and Veit (2020) argue that temporal ordering per se improves welfare, "Intuitively, most people feel like (all other things being equal) a life that begins poorly and ends well is better than a life that begins well and ends poorly; there is value in an upward trend and disvalue in a downward one" (p. 7). Thus, the severe harms associated with the transportation and slaughter of farmed animals are even worse in virtue of their positioning at the end of life, where a bad ending cannot be compensated for with a positive experience (p. 8). Browning and Veit (2022) see widespread evidence that a special aversion to good-to-bad trajectories shapes attitudes towards death. For instance, palliative care focuses on making the dying feel comfortable, which they interpret to show "a special emotional link to the experiences at the end of life. We do not want ourselves, or those we love, to suffer at the end of their lives" (p. 12). Similarly, the common practice of giving prisoners on death row a final meal of their choice (p. 12) could reflect a stronger desire to mitigate the badness of their death than to mitigate the badness of their imprisonment. 

It is not immediately clear how to refine hedonism to incorporate information about whether the instance of suffering occurred at the end of an individual's life. Browning and Veit (2022, p. 12) themselves do not seem to think that trajectories should swamp the calculus: 

We take the emotional reaction to be an additional important consideration informing our treatment of animals and thus for investing resources into improving end-of-life welfare. This of course does not imply that we should do so if it makes the world much worse overall – if we could use the same resources to stop some much greater amount of suffering at another point in time – but simply that, all else being equal, we should pay special attention to end-of-life welfare, rather than write it off as less important.

One way to apply the "all else being equal" clause is to consider the trajectory of experience only when the welfare issues being compared cause an equivalent amount of harm, as measured by severity and duration. However, different experiences seldom cause the exact same amount of suffering, which would render trajectory considerations inapplicable in most situations. One could instead interpret "all else being equal" to mean that the shape of life has an impact on moral badness "holding other factors constant," such as the severity and duration of suffering.  

A remaining issue is that amending hedonism to account for the trajectory of experience allows for transport and slaughter to be viewed as, if not euthanasia, at least relatively merciful: If end-of-life suffering is less bad than the average suffering that the individual endured up until then, then the moral badness of end-of-life will be reduced relative to considering only the severity and duration of transport and slaughter. Browning and Veit (2020) would object to this implication because they believe that slaughter, no matter how painless it is, is morally bad because it causes death (p. 3). However, they could stipulate that the goodness of positive trajectories is subject to constraints such as not causing a premature death.


Although Browning and Veit (2022) base their claim that end-of-life welfare is particularly important on human preferences, they argue that humans can judge on behalf of animals what is worse for them: "It need not be the case that the individual subject of the life is able to judge their life's overall shape and form a preference (or not), only that it would be reasonable for one performing such an evaluation on their behalf to come to such a conclusion" (p. 11). In this section, we provide a reason for questioning the claim that there is a straightforward intuition that the temporal order of experience matters. Following that, we argue that even if humans do have intuitions about temporal order per se, there is an evolutionary debunking argument that can invalidate the apparent contribution of temporal order to welfare.  

A Basic Preference?

As evidence that at least humans have temporal order preferences, Browning and Veit cite a thought experiment in which one can choose between a drug that first causes pain for half a year then pleasure for half a year or vice versa; they infer that most would prefer for pain to give way to pleasure (2022, p. 10). This could be due to the peak-end rule, whereby the most intense part of an experience and its ending loom larger than either the average or total amount of pain. Browning and Veit (2022) maintain that the peak-end rule may reflect a genuine preference regarding the temporal order of pain, rather than the alternative explanation that it is due to a bias in judgment or memory (e.g., Liersch & McKenzie, 2009). 

Putting aside the fact that empirical research has not been conducted to establish what percentage of people prefer the drug that causes pain first and pleasure second, it is possible that the emotions people normally have as a result of registering a change between positive and negative states could distort intuitions about the case. For example, Leknes and Tracy (2010) report that the cessation of pain produces positive affect: 

In brief, the results from our laboratory confirm the predictions stipulated in the opponent process theory as follows: (1) The sudden termination of a painful sensation elicits positive affect, as measured by subjective ratings of relief pleasantness. (2) The relief associated with the offset of pain increases with the intensity of the pain sensation. (3) The pleasantness of relief from pain increases with the efficacy and speed of return to homeostatic balance, as evidenced by the higher positive hedonic ratings when the skin is gently cooled after burning heat pain.

With this as backdrop, imagine the following thought experiment. Two organisms live identically long lives before painlessly dying after 100 seconds. Each organism experiences 50 seconds of painful stimulation (a heat thermode at a mildly unpleasant temperature), and 50 seconds of pleasurable stimulation (a gentle, pleasant, tickle). Organism A experiences 50 seconds of the pleasurable stimulation first, followed by 50 seconds of painful stimulation, and organism B experiences 50 seconds of the painful stimulation first, followed by 50 seconds of pleasurable stimulation. The way the thought experiment is supposed to work, we are meant to assume by stipulation that both organisms experience the same amount of pain and pleasure. However, given the above empirical evidence, it seems highly likely that organism B would in fact experience more pleasure overall, because the cessation of pain for organism B would itself produce positive valence, adding to the positive valence of the stimulation. And if the cessation of a positive experience is experienced as aversive, that would favor organism B's experience even more. Given this, it is not entirely clear how to make experiences with opposing trajectories entirely comparable in terms of the amount of pain and pleasure. As a result, it is difficult to know whether intuitions about thought experiments of this sort are driven by beliefs about the value of a positive trajectory of experience, or instead about how much pain and pleasure result from different trajectories in practice.

Browning and Veit (2022) have more faith in the ability to make intuitions about hypothetical situations that by stipulation differ from everyday life. In defending their intuition that a drug that induces pain then pleasure is better than a drug that induces pleasure they pain, they write, "While one might object that this can be explained by anticipation effects making the latter case worse, this is ruled out by holding fixed the total amount of pleasure or suffering. It must be the order of events themselves, rather than their additional effects, that we prefer" (p. 10). However, Royzman et al. (2015) point out that "people routinely anchor fictional content in real-world knowledge, finding it difficult to comprehend information about a fictional universe that contradicts their real-world assumptions" (p. 298), and present evidence that many participants do not play along with implausible stipulations when providing their moral intuitions about hypothetical vignettes. In the present case, considering trajectories of pain and pleasure without accounting for anticipation, relief, and comparison with the past requires imagining what the self would prefer if it had radically different dispositions, undermining the experiential basis for making a confident judgment. 

Until behavioral scientists design ways to account for the anchoring effects of past experiences on moral intuitions, thought experiments of this sort are not dispositive. Note that an analogous issue would affect experiments testing whether farmed animals have preferences about the temporal ordering of experience. One could use a conditional place preference test in which animals choose to move towards either a location that they associate with a good experience and then a bad experience, each of which lasts the same amount of time, or a second location where a bad experience gives way to a good experience of the same duration. But the second location might be preferred because it is associated with greater pleasure and less pain, once effects such as relief and anticipation are taken into account. 

Evolutionary Debunking

 In spite of our claim that humans would struggle to hold net welfare constant, it could turn out that many people would earnestly affirm that the trajectory of experience matters. In this case, one would then need to evaluate whether this preference is based on a valid moral intuition. Browning and Veit (2022) suggest that the kindness and mercy humans show for those at the end of their life reflects compassion: "It is some sense of compassion or benevolence that motivates the desire for someone to have a pleasant experience with which to finish their lives" (p. 12). We suspect that inferring moral values based on which situations evoke compassion is an unreliable process for detecting moral truths because compassion arguably evolved in part to facilitate helping individuals who only temporarily need help, and who will likely eventually have the resources to return the favor (Goetz et al., 2010Trivers, 1971). Consequently, sudden need evokes more compassion than chronic need, as the chronically needy are less likely to ever reciprocate. As Delton et al. (2018, p. 919) explains, prioritizing helping those whose welfare has suddenly declined is inefficient when scaled to the societal level:

When asked to reflect on the matter, people would probably agree that social welfare spending should be primarily targeted at the neediest citizens. But the acute-needs heuristic focuses attention on different targets: people who have fallen far even if they are still doing well in absolute terms. Hence, this heuristic could cause citizens to support policies that target relatively well-off people, at the expense of the neediest. 

Although it could be true that it is more aversive for rich people to experience the same absolute amount of deprivation than the less well-off, it is far less plausible that, as a policy, preferentially directing aid towards those who suddenly have less less wealth over the chronically least-well-off produces the greatest direct welfare gains. 

The perverse consequences of compassion's evolved sensitivity to sudden decrements in welfare suggests that it is a poor guide to moral reasoning, a conclusion that even those under the influence of compassion have admitted to in an experimental setting (Batson et al., 1995). If so, then the fact that a preoccupation with end-of-life welfare is driven by compassion should count against its validity. Browning and Veit might object that compassion towards those at the end of their life is inconsistent with the evolutionary explanation proposed here because people who are dying cannot return favors. However, emotions evolve based on whether they increase inclusive fitness, averaged across ancestral populations and environments, not whether they optimize behavior on any one occasion (Sznycer et al., 2019). Increasing the complexity of the computations that determine whether an emotion triggers will only be selected for to the extent that the fitness benefits of doing so more than cover the additional metabolic costs. Callousness towards those suffering at the end of their lives is not obviously personally beneficial, insofar as emotions signal good character to third parties only if they are perceived as not due to self-interested calculation (Trivers, 1971Frank, 1988).

One could also object that debunking arguments prove too much: All moral beliefs are open to debunking arguments, including tenets of hedonism such as that suffering is bad (Kahane, 2014; but see de Lazari-Radek & Singer, 2014, pgs. 266-269). For present purposes we could easily bite this bullet, as we are not advocating for any alternative moral values here, or even moral realism. Nevertheless, it merits mention that how much a debunking explanation undermines the justification in a moral belief depends on whether one would reason their way to that belief even if it had not evolved via natural selection. Our doubts about the moral relevance of the trajectory of experience depend not only on the fact that we were able to formulate an evolutionary hypothesis to debunk it, but also on our inability to see how reasoning from premises that cannot be debunked would lead to an intrinsic valuation of bad-to-good sequences over good-to-bad sequences. 


Browning and Veit's case for prioritizing improving the humaneness of transport and slaughter of farmed animals depends on welfare at the end of life having more intrinsic welfare importance than earlier parts of life. However, the intuition that the trajectory of experience matters morally depends on a human intuition that may be unduly influenced by morally irrelevant factors. Until there are independent grounds for placing intrinsic importance on end-of-life welfare, it would seem imprudent to shift resources towards reforming transportation and slaughter, if one believes that more suffering could be prevented overall through other means.  



This research is a project of Rethink Priorities. It was written by William McAuliffe and Adam Shriver. We thank Marcus A. Davis and Holly Elmore for helpful feedback on earlier versions of this report. Also, a special thanks to Michael St. Jules for providing quality control throughout the writing process.


Batson, C. D., Klein, T. R., Highberger, L., & Shaw, L. L. (1995). Immorality from empathy-induced altruism: When compassion and justice conflict. Journal of Personality and Social Psychology, 68(6), 1042–1054.

Browning, H., & Veit, W. (2020). Is humane slaughter possible? Animals10(5), 799.

Browning, H., & Veit, W. (2022). The importance of end-of-life welfare. Animal Frontiers, 12(1), 8-15.

de Lazari-Radek, K., & Singer, P. (2014). The point of view of the universe: Sidgwick and contemporary ethics. OUP Oxford.

Delton, A. W., Petersen, M. B., DeScioli, P., & Robertson, T. E. (2018). Need, compassion, and support for social welfare. Political Psychology39(4), 907-924.

Frank, R. H. (1988). Passions within reason: The strategic role of the emotions. WW Norton & Co.

Goetz, J. L., Keltner, D., & Simon-Thomas, E. (2010). Compassion: an evolutionary analysis and empirical review. Psychological bulletin136(3), 351.

Kahane, G. (2014). Evolution and impartiality. Ethics, 124, 327-341.

Leknes, S., & Tracey, I. (2010). Pain and pleasure: Masters of mankind. In M. L. Kringelbach & K. C. Berridge (Eds.), Pleasures of the brain (pp. 320–335). Oxford University Press.

Liersch, M. J., & McKenzie, C. R. (2009). Duration neglect by numbers—and its elimination by graphs. Organizational Behavior and Human Decision Processes108(2), 303-314.

Royzman, E. B., Kim, K., & Leeman, R. F. (2015). The curious tale of Julie and Mark: unraveling the moral dumbfounding effect. Judgment & Decision Making, 10(4).

Sznycer, D., Delton, A. W., Robertson, T. E., Cosmides, L., & Tooby, J. (2019). The ecological rationality of helping others: Potential helpers integrate cues of recipients' need and willingness to sacrifice. Evolution and Human Behavior40(1), 34-45.

Trivers, R. L. (1971). The evolution of reciprocal altruism. The Quarterly review of biology, 46(1), 35-57.



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Yes, some interesting thought experiments. Here's another- imagine there is a method that cures chronic pain, we don't know why because we don't know enough neuroscience and psychiatry (yet). The method may have been  proposed by James Pennebaker,  John Sarno, Howard Schubiner, Alan Gordon or (my personal favourite- it worked for me) David Hanscom but we don't know because we haven't done any trials because all these ideas sound crazy and none of us want to be linked with something that sounds crazy.

So it's possible we have the solution (or a solution for some/many/most- who knows) people but noone can organize a proper trial- would this not be a good practical way to make the world a better place? Who's in?