A Glitchy Piece of Flesh
Sentience occurs when an organ associated with directing emotional responses gets so dense that it glitches and removes the element of -time- from the equation.
So, instead of an (a) a smoky fire burned you, (b) you smell smoke, and (c) you react to the fire, another step pops in. (b-2) ‘Memory’ removes this strong experience from time and embeds it in a lump of flesh.
Consciousness is the shallowest of all of the intelligences. Memories, as we understand them, exist as just persistent whirlpools that appear when strong experiences clump together.
And personalities? Much of what we think of as personalities are made up when strong memories press together. With an added bonus of a a little cheat that tells us we’re one, whole being rather than this odd collection.
So, sentience is the most shallow experience and glitchy, but it’s power lies in its flexibility. It anticipates issues long before they actually occur. Sentience plans. It can affect itself, which is to say, the emotions and physical reactions, all the way down to epigenetic changes.