I've just finished implementing the personality system in Software Inc! The personality system is a graph of personality traits, describing their relationship with each other and their attributes. Each employee in the game gets two personality traits.
The graph is of course moddable, so you can add traits and decide their attributes and relations.
I've illustrated a tiny piece of the current graph in the image above. The circles are personality traits, the color of the arrows between them indicate how they regard each other, the colors of the rows in table next to the circles illustrate how a trait influences the employee and the color of the circles indicate their compatibility.
As an example, say you have the mean trait, then you will have aptitude, bad leadership skills and average diligence. Being mean also makes you dislike people who are generous and optimistic, and feel indifferent towards people who are pessimistic. Finally, if you are mean you can also be pessimistic or optimistic, but you can't also be generous, since the mean circle isn't blue or green. Note that this is not necessarily how it works in the real world, but the point is to give the player an intuitive sense of an employee based on her personality traits and these relationships are subject to change.
So what difference does having personality traits make? When you put an employee on a team, her traits will be weighted against the other members of the team, determining how well she works together with the other members. If she dislikes a person on her team she might get angry and want to quit. Overall bad team compatibility will have an effect on your employees' work quality, but a good team leader can alleviate the problem.
So what does aptitude, leadership and diligence mean? Well, each personality trait changes the characteristics of its employee, which affects their stats and behavior in the game. Currently aptitude, leadership and diligence are the only three characteristics, but the system allows me to expand these at any point, although they are not moddable. Aptitude controls how quickly an employee gains skills and education, leadership controls how well a leader does his job(research, employee satisfaction, etc.) and diligence controls how late an employee is and how often the employee calls in sick.
