Pain is officially defined as, “An unpleasant sensory and emotional experience associated with actual or potential tissue damage,” yet is experienced differently by each person and organism. Because of this it is extremely difficult to describe just how an animal experiences pain. To study how an animal experiences pain “argument-by-analogy” is applied. This means if the animal reacts in a similar way to how we would, we believe they are experiencing pain.
An example of this is if a dog was pricked with a pin and ran away, just as a human would. The strange thing with insects is that they have no capacity to feel pain at all! Nociceptors are what carry the feeling of pain to the brain. These are essential to experience pain, yet insects and crustaceans have never been found to have any! This means most of these animals are unable to feel any sort of pain!