Sentience

Sentience, or intelligence, was a classfication based on the ability to think intelligently. Sentient species included Humans, Ithorians, and Aqualish. Non-sentient species included bantha, keeradaks, and tauntauns.

Sentient species
Various sentient species were commonly found throughout the entire galaxy, from cantinas to offices, to military ships to apartments. These species had a set language used to communicate with each other, usually learnable by any species. Although all sentient species had a form of communication towards others of the same species, it was sometimes unlearnable by members of other species, usually because it was too complicated for a certain species' throats. Another more rare reason was that the language was only capable of being spoken through a certain ability or organ built in one species, such as telepathic connections in their brains. However, such species were still common to be seen anywhere, living peacefully with others. Sentient species' brains were much more complex than non-sentient species'. They were capable of advanced self-awareness, consciousness, and perception, and were more intelligent and capable of solving complex problems. This was most active in the cerebrum, a part of the brain less complicated in non-sentient species. The complexity of the neocortex was also a crucial factor in sentient species, another component of the brain less complex in non-sentient species. The neocortex was responsible for reasoning and language, among other things.

Non-sentient species
Non-sentient species were astronomically greater in numbers and species, although they rarely left their homeworlds unless domesticated. They were commonly referred to as animals or creatures (despite the fact even sentient species were animals), and were unable to think intelligently. They had less complicated cerebrums and neocortices, as well as less complicated brains in general. Some non-sentient species were intelligent enough to be compared to younger forms of sentient species. This was, however, rare, and very little could be compared to the intelligence of a human over ten years of age.

Semi-sentient species
Some species could be classified as semi-sentient. Semi-sentient species seemed to be able to think intelligently to a degree, with a clear language, albeit simple. Kowakian monkey-lizards were an approved example of semi-sentient species, used popularly as pets for wealthy individuals.