Animal Sentience

Pigs

Sus scrofa domesticus

Pigs demonstrate cognitive abilities in specific domains--such as spatial memory, object discrimination, and social learning--that are sometimes compared to those of young children or dogs. However, cross-species cognitive comparisons are inherently limited, as different species excel in different domains (Marino & Colvin, 2015).

Insects

Evidence for insect sentience is growing but remains less certain than for vertebrates; a precautionary approach is reasonable. Veganism typically reduces direct harm to large, clearly sentient animals and reduces land use—likely reducing many forms of animal suffering overall, including incidental insect deaths.

Cephalopods and decapod crustaceans

Many jurisdictions and scientific reviews increasingly recognize strong evidence for sentience in cephalopods and decapod crustaceans (e.g., learning, flexible behavior, responses consistent with pain). This has driven policy recognition in some places.

Fish pain (with uncertainty/disagreement)

Fish pain is one of the most actively debated topics in animal welfare science. Sneddon (2003) identified nociceptors in rainbow trout, and fish show prolonged behavioral changes after painful stimuli. However, Rose (2002) and Key (2016) argue fish lack neocortical structures for conscious pain. The 2024 New York Declaration on Animal Consciousness (500+ signatories) concluded there is "at least a realistic possibility" of conscious experience in all vertebrates, including fish. The weight of evidence tilts toward fish having pain capacity, but genuine scientific disagreement remains.

Mammals and birds

The scientific mainstream accepts that mammals and birds have the neurological and behavioral capacity for pain and other affective experiences. This is reflected in broad scientific consensus statements and welfare science.