Benefits: The use of related stimuli is the gold standard for inducing artificial emotions across practically every media known to man. Great novels, paintings, movies, and poems rely on their intense portrayals a human experience that is not our own, but close enough to tap into our personal experiences. As a creator, this is technique is quite cost effective and most of us have been trained in its application.

• You can craft a single static experience that is broadly applicable to your audience. You don’t have to worry about customizing your message. They’ll expend the effort to find meaning.
• You can rely on your personal experience for inspiration. This isn’t because you are special. Instead, it is because whatever you come up with will likely be close enough to what someone else has experienced. Humans are limited in what they can experience. If you describe how you are feeling when you are sad or happy, you are likely also describing how others are feeling when they experience those same emotions. This greatly reduces the need for detailed customer feedback, an expensive activity.
• You can be sloppy. Relevant stimuli is like using a shotgun. Whatever you make is likely to be meaningful to someone in the audience. A wide range of modern art and music plays on this loophole by showering people with ambiguous messages. A small percentage ‘gets it’ and that is enough to pay the bills.
• Setting up cognitive labels. If all else fails, relevant stimuli can still at least set up the appropriate context for interpreting the experience. Even if the player doesn’t tap into existing spiritual experiences, they at least understand from the overload of religious symbols that they participated in some sort of religiously-themed activity.

Limitations: Relevant stimuli is amazingly powerful, but has some limitations when it comes to use in games.

• High burnout. After a very short period of exposure, players start ignoring relevant stimuli. Techniques like avatar mapping and other user-generated content strategies can keep content fresher, but replacing consumed content is still a costly issue to consider.
• Limited interactivity. Traditional forms of relevant stimuli do not change with the user’s input. Movies, narratives and images are all about evoking a response, but they have no ability to adapt once the player responds.
• Unpredictable. It is hard to guarantee that relevant stimuli will produce the desired emotional response. Look at the case of Harry Potter. Most saw the first book as a charming schoolboy romp and identified with its stimuli targeting their own feelings adventure, mystery and coming of age. Others saw it as an obvious promotion of witchcraft and Satanism. They reacted with anger and fear. What your audience brings to the work has a huge impact on how it is interpreted.

Technique 3: Biofeedback

"She begins to dance. At first her movement is controlled and intricate. The screen pulsates and she yells to its beat."

Not all techniques at our disposal create both a physiological response and cognitive labels. There are some that just do one or another. Such techniques can be used as building blocks in a larger system.

One well-studied technique that affects that body is bio feedback. This is particularly interesting to game developers since it is a fundamentally interactive technique and offers deep opportunities for mastery-focused gameplay.

A surprising number of automatically controlled systems can in fact be influenced consciously. The most obvious one is breathing, as seen by pearl divers holding their breath. Other systems can be controlled indirectly by consciously adjusting related systems. For example by staying stationary, slowing your breathing and thinking calming thoughts, you can slow heart rate.

If only we could encourage the player to directly control their physiological state, they could

consciously put themselves in a state that was conducive to feeling the desired artificial emotions. Unfortunately, people are generally quite poor at recognizing and attaining mastery over systems such as the autonomic nervous system that have poorly-visible second order effects that are only loosely connected to the original action. Most people couldn’t tell you their heart rate and even fewer could tell you how they could consciously speed it up or slow it down.

We see this problem of controlling second order effects pop up in games all the time. Suppose you add a switch that unleashes an AI monster, that then steps on a switch that opens a door off screen. The end result is that users complain that they have no idea why things are happening. The chain of events between cause and effect is too long and confusing for the user to form a testable mental model of the system.

In order to teach the user how to control second order interactions, the game designer has to provide lots of clear, concise feedback and plentiful rewards for the right actions. Biofeedback applies these game design principles to the task of influencing the autonomic nervous system.

• Clear, concise feedback through biometrics. Most people are not conscious of their pulse. By instrumenting it with a simple heart rate monitor, we can turn an invisible outcome into a clearly visible outcome. If the player jumps up and down, they see their heart rate increase. Biometrics take a little of the mystery out of the player’s physiological state.
• Plentiful rewards. Players will stumble upon the techniques that make the metrics change. Once the player jumps up and down and their heart rate increases, you want to let loose the fireworks. The player needs to know that whatever they just did is a good thing, even though it may not be obvious why it was a good thing.