Theoretical descriptions of cognitive neoassociation date back several decades in the social sciences and it gets leveraged fairly consistently in the realm of game design, in most cases inadvertently. The theory posits that memories are built from personal interpretations of events. What this means is that new memories are based on the prior interpretations of past events, and so on, back until the earliest memories, which relate more to quantifiable response. For example, you take a sip from a cup of hot cocoa and it stirs up in you memories of holiday parties you attended as a child and perhaps you remember other specifics about those holidays. This is because you have associated the taste of hot cocoa with a specific time or event and all of it's interlocking memory artifacts. Similarly, you know to be careful drinking from the hot cup because you have a history with hot surfaces and beverages going back to the first time, as a young child you drank or touched something that was too hot. You can't see temperature, but you've codified high temperatures with other signifiers such as steam or condensation. While the basic principals are probably pretty well understood innately by most game designers, knowing the reason why people react in specific ways to the virtual situations we put them into can help us to better craft those situations to elicit the most appropriate response.
In most cases the effects of memory association don't need to be overly direct or ham-fisted, it's not necessary to hit the player over the head with stereotypes for evil or good. It's true that for a character like Bat-Man's The Joker, his psychosis plays a large role in his over the top and overtly crazy behavior. Depending on the theme of the game or even the specific character, a literal representation of archetype like this may be the best choice, but a more subtle approach can also have a significant effect on player reaction. In the Metal Gear Solid franchise, Revolver Ocelot is an example of a character who seems very rational, but at the same time is clearly a bad guy. The context in which Snake encounters Revolver Ocelot helps to define his character as opposed to outright villainous behavior. One of the reasons this more subtle approach works is thanks to the phenomena of priming.
Priming, in terms of reaction elicitation, is a method by which a subject (in this case the player) is preconditioned to react to an act or event in a specific way. In game designer's terms this means that if you preface an event with depictions of negative behavior, the subsequent scene will be interpreted as darker or more ominous by the player, as opposed to a scene which follows a demonstration of positive interaction by the parties involved. A great example of this in video games can be seen by examining the two playable factions in Call of Duty 4: Modern Warfare. When playing as American marines the player is treated to lots of "Hoo-Ah's" and sometimes thuggish machismo, the British SAS forces on the other hand are much more serious and thoughtful as they go about what is essentially the same business. The result of this is that as the Marines stumble through the game, constantly botching jobs, we begin to see them not as overwhelmed and under supported, but as childish brutes. This is in comparison to the refined and professional interpretation of the SAS. While the SAS interactions are designed to emphasize the use of stealth, it is not necessary to remain undetected and the action of shooting enemies when playing as either faction is the same for the player. The difference in the mood of the separate game stories is caused by the differences in priming associated with each group.
In order to effectively prime a player, situations must be designed to take into account the players background, culture, and the residual effects of other priming that has happened previously in the experience. Different actions and events have different significance in different cultures, and while most developers are making games for their cultural peers, it's important to remember that messages may not have the same strength with different audiences. More importantly, priming effects have a shelf life; all else being equal more recent priming effects will have a larger effect than previous priming. Given, if you have a character murder a child in one scene, then buy a kid a candy bar in the next scene, the killing is going to have a distinct effect on the interpretation of future actions of that character, but even this example on it's own can display the results of a priming effect when compared to either scene viewed separately or ordered differently. One of the most notable examples of priming effect as demonstrated in the social sciences was a study done by Wendy Josephson in which she primed juvenile subjects by showing them violent media featuring walkie talkies. The subjects were then directed to participate in floor hockey games. In some games the referees had walkie talkies, in some they did not. In the instances in which the authority figures were carrying the pre-associated violence indicator (the walkie talkie), the subjects were much more aggressive in their play than when there were no such indicators present. What this study demonstrated was that priming effects can be very subtle. For example, if you give lappel pins to characters who are committing violent acts throughout the course of a game, then put the player in a situation where he has to eliminate a target in a crowd of people all wearing lappel pins, you can assume that they are going to act more aggressively than they would against a crowd of non-pin wearers. The key to remember when utilizing priming to set up a desired reaction is that as the story progresses, every event should be viewed as leading up to something, even if it's relatively mundane. Keeping in mind the cycle of priming events and reaction events can also help with pacing and overall story flow as the game progresses.
One final factor to be aware of in the area of cognitive association and memory is that, as interaction designers, we have some control over the strength of the reactions that we elicit. Specifically, by linking physical experience to an observed reaction the observer's interpretation of that reaction is strengthened. This means that by not just showing something visually but by adding a phisiological trigger to the event the ability of those actions to trigger and form memory connections will be strengthened. The insanity effects used in Eternal Darkness rely heavily on sound design in addition to unsettling visuals to elicit a more profound response from the player. The utilization of force feedback technology is a very common way to leverage this effect. Controller shake based on being hit or firing is relatively common in FPS games, and using controller shake to mimic on-screen camera shake also works on the same principal. In a more subtle implementation, Rez uses the vibration system to pair physical vibration to audio and visual queues of the game to strengthen the overall reaction to play.
Regardless of the nature of the priming feature utilized, the goal of any story-based game is to tell its story in a memorable way. Understanding how to properly implement the ideas behind cognitive neoassociation theory within the context of a game world can make those memory-forming reactions more meaningful. Relating new in-game experiences to existing memories will make player reactions to in-game situations more profound and help form lasting memories of the game.
For further reading on cognitive neoassociation, I recommend the following articles:
Some Effects of Thoughts on Anti- and Prosocial Influences of Media Events: A Cognitive-Neoassociation Analysis. Burkowitz. 1984Television Violence and Children's Aggression: Testing the Priming, Social Script, and Disinhibition Predictions. Josephson. 1987