Introduction





In this study, we wanted to determine how people view the sentience (the ability to feel pleasure and pain) of fish relative to other non-human animals, humans, and inanimate objects. How intelligent do people think fish are, and how do they regard a fish’s ability to feel mental and physical pain or pleasure?





This information should provide some useful baseline knowledge for farmed animal protection organizations like Mercy For Animals who strive to reduce the cruelties inflicted upon fish (especially farm-raised fish) and reduce fish consumption.











Method





We surveyed 300 participants using Amazon Mechanical Turk. Participants were asked to rate six different species on their intelligence and ability to feel physical pain, mental pain, and mental pleasure. All answers were on a zero to 10 scale, where zero indicated no intelligence or ability (such as an inanimate object, like a rock) and 10 indicated intelligence or ability similar to that of a human.





To calibrate the survey’s ratings, all participants were first asked to rate chimpanzees. The other five animals—pigs, cows, chickens, dogs, and fish—and the general term “plants” were then presented in random order.







After rating the animals and plants, participants were asked to roughly indicate how frequently they ate certain foods.







We analyzed 293 completed responses using t-tests and Spearman’s correlation, with p-values adjusted using the Holm-Bonferroni method.











Results





Perceptions of Animals







Unsurprisingly, participants rated chimps and dogs closest to humans on all measures, and they rated fish as the animal with the lowest levels of sentience. Participants generally ranked all animals in the same order for each of the measures, from greatest ability to least: first chimps, then dogs, pigs, cows, chickens, and finally fish. Plants were ranked lowest.







Fish were rated close to chickens in regard to intelligence but were rated as having significantly lesser abilities to feel pain (both physical and mental) and pleasure relative to other animals. Fish were rated significantly higher than plants on all measures, but they were still rated closer to plants than to chimps or dogs.







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Relationship Between Diet and Perceptions of Animals







In general, the results indicate a negative relationship between meat consumption and ratings of animal intelligence and ability to feel physical pain, mental pain, and pleasure. The more meat a participant reported eating, the less intelligent and less able to feel pain and pleasure they rated animals of all species. This relationship seems particularly strong for beef consumption. (There was a statistically significant negative correlation between beef consumption and perceptions of intelligence and ability on at least one of the four measures for all animals except fish, and on all measures for pigs.)





Conversely, there is a generally positive relationship between vegetable, fruit, and dairy consumption and ratings of species’ intelligence and ability to feel pain and pleasure.







There is a weak positive correlation between fish consumption and perceptions of fishes’ abilities, but these correlations are not statistically significant. In other words, participants who reported eating fish frequently were more likely to rate fish as more intelligent and able to feel pain and pleasure. As noted, these results did not reach statistical significance. But if this correlation exists, it would run counter to expectation based on the results for other species. Of course, correlation does not imply causality; one factor could be causing the other, or a third factor could be driving both.







Chart Notes



Red indicates a negative relationship (i.e., higher consumption is correlated with lower animal sentience ratings); the darker the red, the stronger the relationship.

Blue indicates a positive relationship (i.e., higher consumption is correlated with higher animal sentience ratings); the darker the blue, the stronger the relationship.

White indicates a weak or no relationship.

IN = intelligence PP = physical pain MP = mental pain PL = pleasure

















Conclusion





The results of this study show a clear hierarchy in how people view the sentience of different animals, with fish below the other main farmed animal species: chickens, pigs, and cows. Dogs and chimps are seen as being close to humans in their intelligence and ability to feel pain and pleasure, while chickens and fish are viewed as having significantly lesser abilities. In many cases, participants rated chickens and fish as being closer to plants in their abilities than to humans. Pigs and cows are seen as having abilities somewhere in the middle, between dogs or chimps on the high end and chickens or fish on the low end, with pigs seen as having greater abilities than cows.





The results also provide unsurprising evidence that the more meat a person eats, particularly beef, the less likely they are to perceive animals as intelligent or having the ability to feel pain and pleasure. But this relationship appears to be the opposite for fish; compared with people who rarely consume fish, people who frequently consume fish may view them as more intelligent and able. Although this correlation was not statistically significant, it is worth noting as it may have implications for attempts to reduce fish consumption or improve the treatment of fish.









