Sentience

Some living things can feel.

This is called sentience. It means they feel things like joy or pain.

Many animals have this. Fish and reptiles can feel. Even some bugs can feel too.

Scientists look for clues. They watch how animals act. A dog might lick a hurt paw. This shows it feels something bad.

Octopuses are smart. They have felt things for a long time.

They are very special.

Because they feel, we should be kind. We should help them stay safe and happy.

What does it mean to feel? Scientists call this sentience. Sentience is the ability to feel sensations and emotions. This might include feeling things like pleasure or pain. It does not always mean an animal can think in complex ways.

Many animals are likely sentient. This includes all vertebrates, like fish and reptiles. Many invertebrates are also sentient. This group includes insects and octopuses.

In 2023, the United Kingdom recognized octopuses as sentient. Scientists look for clues to find this. One way is to study nociception. This is the way a nervous system finds and reacts to harm.

If a dog licks a hurt paw, it shows the dog feels something bad. Bees can even show moods. They might act in a playful way.

Sentience is also important in religion. In many Eastern religions, living things are seen as sentient. This idea helps people follow rules of non-violence. Because animals can feel, many people believe we must treat them with care.

Sentience is the special ability to experience feelings and sensations. This means a living thing can feel things like pleasure or pain. It is different from being able to reason or solve hard problems. Some thinkers say sentience is only about having positive or negative feelings. This idea is very important for how we treat others. If a being can feel happiness or suffering, we might owe it care.

Scientists use many clues to see if an animal is sentient. One way is to look for nociception. This is a thing that happens when a nervous system finds harm. Special parts called nociceptors sense a threat and send signals to the brain. We can also watch how an animal acts. For example, a dog might lick a hurt paw or limp. A bee might even show an optimistic mood or play.

People have studied these ideas for a long time. Philosophers first used the word sentience in the 1630s. It comes from a Latin word that means feeling. In the late 1970s, Robert A. Freitas Jr. made a new idea called the sentience quotient. This is a way to measure sentience using math. It looks at how fast a brain processes information. It can even be used to talk about computers.

Many different animals are now known to be sentient. All vertebrates, like fish and reptiles, have the brain parts for consciousness. In 2012, a group called the Cambridge Declaration of Consciousness shared this finding. Later, in 2024, the New York Declaration on Animal Consciousness was signed by over 500 scholars. They said there is strong support for consciousness in birds and mammals. They also believe insects and octopuses likely have it too.

Sentience is also a big part of many religions. In religions like Buddhism and Hinduism, many living things are seen as sentient. This idea is linked to ahimsa, which means being non-violent to others. In Jainism, even water is seen as a sentient being of the first order. This is because water is thought to have the sense of touch. These beliefs help people decide how to live kindly with all life.

Sentience is the capacity to experience feelings and sensations. This includes the ability to have subjective experiences, such as feeling pleasure or pain. It is important to distinguish sentience from higher cognitive functions. These functions include things like reasoning, complex thought, or self-awareness. While a being might be very intelligent, it does not necessarily mean it is sentient. Some theorists define sentience specifically as the ability to have valenced experiences. Valence refers to whether a mental state is positive or negative.

Scientists use several methods to study how sentience works in living things. One key process is nociception, which is how a nervous system detects harm. Specialized receptors called nociceptors sense a threat or damage. These receptors then send signals to the brain. While nociception is a physical process, researchers want to know if it leads to a subjective feeling of pain. To find out, they look for behavioral cues. For example, a dog might limp or lick a wound. A bee might show an optimistic mood or engage in play.

There are different ways to categorize the types of consciousness. David Chalmers describes two main ways to look at it. One is phenomenal consciousness, which is the capacity to have any subjective experience at all. The other is affective consciousness, which is a narrower concept. This focuses on states with affective valence, such as the ability to feel suffering or happiness. Philosophers also debate the nature of these experiences. Thomas Nagel argued that consciousness involves subjective perceptual experiences, often called qualia. Qualia are states that feel like something to be in.

Research into animal sentience has grown significantly over the years. In 2012, the Cambridge Declaration of Consciousness was released. It stated that many non-human animals possess the neurological substrates for conscious states. This includes all vertebrates, such as fish and reptiles. In 2024, the New York Declaration on Animal Consciousness was issued. Over 500 scholars signed this document. It affirmed strong scientific support for consciousness in mammals and birds. It also noted a realistic possibility of conscious experience in many invertebrates, including insects and octopuses.

Historically, the study of sentience has moved through many stages. Philosophers first coined the term in the 1630s. It comes from the Latin word "sentiens," which means feeling. In the late 1970s, Robert A. Freitas Jr. introduced the sentience quotient. This is a mathematical way to measure sentience. It looks at the information processing rate of individual units, like neurons. It also considers the size of the units and the total number of units. This scale can range from -70 to +50. It can be applied to everything from a single neuron to a hypothetical computer.

Sentience is a central idea in many ethical and religious systems. In the animal rights movement, Jeremy Bentham famously asked if animals can suffer. This idea helps determine which entities deserve moral consideration. In the European Union, animal sentience was written into basic law in 1997. This requires member states to respect the welfare requirements of animals. Eastern religions also recognize sentience in many forms. Hinduism, Buddhism, Sikhism, and Jainism all recognize non-humans as sentient. In Jainism, even water is considered a sentient being of the first order because it has the sense of touch.

Finally, the concept of digital sentience explores whether artificial intelligence can feel. This remains a controversial topic in the scientific community. Most AI researchers focus on programs that behave intelligently. They aim to program awareness or attention, but they do not view making a machine feel sensations as a primary goal. Leading AI textbooks often do not mention sentience at all. This is because it is difficult to prove if a machine is truly experiencing a sensation or just processing information from sensors.