Cores

Aperture Science Artificial Personality Constructs, also known as personality constructs or more commonly as cores and spheres, are programmed artificial intelligence designed to either give the central core emotions or do a certain job based around their personality.

Cores can become corrupted overtime from the cause of certain reasons, such as becoming obsessed with something, tricking themselves into thinking they're a certain someone or saying slightly true, nonsensical and illogical factoids.