Some games do not feature full conversation systems, but merely simple means for interacting with characters that pass by. Often, interacting with NPCs in this way is part of the same gameplay used for exploration, combat, etc. The game does not change into "conversation mode" when it comes to NPC interaction.
In many cases, the player chooses a gesture or attitude to take when initiating interaction with an NPC. The NPC responds briefly, and sometimes the player has the opportunity to choose another gesture or attitude.
Often, the player rarely has more than two interactions with a given NPC in one of these encounters, which are typically carried out for the purpose of an immediate reward, such as a health boost, like in Bully or a temporary bodyguard, such as in Grand Theft Auto: San Andreas.
It is possible for these interactions to have meaning over the long term, however. In Fable, romances are handled by this same sort of system.
The player builds up their relationship with a potential partner by returning to them again and again over the course of the game, choosing the appropriate gestures and giving gifts.
Eventually the player reaches the point where he can propose to the NPC, at which point the NPC sometimes gives gifts to the player.
The transparent nature of Systemic Interactions is the most obvious problem with this method, since the player receives constant reminders of the exact nature and purpose of his interactions, making immersion difficult to achieve.
Another common issue seen in games using this method, though not necessarily inherent to the system, is that NPCs, even the romantic interests in Fable, typically have no real character. Interactions with them are superficial not only due to the nature of the interaction, but because there is nothing to learn about them.
None of the characters have unique responses; every NPC with the same character model has the same voice and dialogue. Bully has several unique characters that express their personality through their responses, but interactions remain shallow.
The implementation of Systemic Interactions in a game is usually made in order to allow the player to deal with a great many NPCs, so making those interactions meaningful is a difficult challenge. The Sims is an example of a system similar to this type that has had great success in this area.
Some NPC interaction gameplay is unique, or difficult to categorize. The Sims is a notable example as the best-selling PC game of all time. While The Sims' basic interactions are very similar to Systemic Interactions, the context is significantly different due to the way the player has control over multiple characters and can control both sides of a relationship.
In The Sims, the player chooses which character to control, and then issues simple commands like "compliment," "brag," or "flirt."
Characters in the game speak nonsensical gibberish, however, so their dialogue reflects only their mood or their emotional response to the topic and the character they converse with; it conveys no other information to the player.
However, using a fictional language avoids the issue seen in many games where the player must endure countless repetition of the same few lines of dialogue.
While the player eventually comes to recognize repeated snippets of gibberish, their nonsensical nature makes them much more palatable.
Conversations in The Sims serve to improve or worsen relationships between characters, with new options opening up on either end of the social spectrum. The Sims also has a more organic form of the Time Scheduling system (described in the next section), as relationships with other Sims worsen when the player ignores them, and the player must determine how they want their player to spend their time.
There are no scripted relationship arcs in The Sims, so the player has complete control over their development and outcome. In this manner, the developers save hundreds of man-hours in writing dialogue while still engaging players with the characters.
The popularity of The Sims and the emotional attachment some players develop may indicate that the freedom of the game leads to engagement, but players tend to make these attachments to characters under their direct control, and therefore these characters are not necessarily NPCs.