Making a game is sometimes like being in a bad relationship. In the beginning, everything ticks along nicely and your partner seems happy as you try and provide for their needs. You both know what you want, and all seems well with the world. After a while however, your partner begins insisting that you spend more time with them, you never seem to be able to do enough, and they become more demanding. Your life soon becomes dominated by a never-ending list of things they want. Fail to give them the care and attention that they dictate, and they stubbornly refuse to do a single thing that you ask of them. Eventually you give in to their requests, secretly plotting to end the relationship as soon as you can, moving on to something better that will allow you the space and freedom you need to truly express yourself. When the split finally comes, it is a relief, but looking back, seeing all the things you achieved together, you realize that through pain there is reward. Next time, however, you won't be pushed around quite so easily.

You may think that this article will address that most insidious of evils: Feature Creep (which to me always sounds like one of Spiderman's less successful foes). This however, was not the purpose of my "a game is like a relationship" analogy. My intended point was that a game (like a relationship) is a complex, dynamic thing that requires the participants to draw on all areas of understanding to make it successful. Similarly, the more involving and well constructed the game world is, the more a player will be drawn in and rewarded.

It is from this point of view that I propose that psychology has a part to play in game development. OK, I can hear you groaning. Psychology: the realm of ink blots and Freudian slips. But stifle that yawn and bear with me. Psychology aims to explain how the mind works, and how this leads you to act, think and experience everything from falling in love to dressing as your mother and attacking women in showers with a carving knife. Whether your game is trying to be a perfect simulation of flying an F-16 or an epic adventure set in a unused carpet factory, understanding psychology can improve your game's design and execution.

Psychological techniques have been effectively used by video games for years, simply because we all live in the same world and decode our surroundings using basically the same physical and mental machinery. Our life's experience brings us into contact with a similar range of emotions, and it is this framework that we draw upon when we create something, whether it be a book, a song or a game. What I suggest is that we put names to these psychological aspects.

So, where to begin? Let's see how the player interprets what they observe and hear.

You Think That's Air You're Breathing?

First of all, a brief overview:

	FIGURE 1. Perception.

Theories of perception generally draw upon the same basic idea. Gregory's definition reads:

"Perception is not determined simply by stimulus patterns; rather it is dynamic searching for the best interpretation of the available data ... perception involves going beyond the immediately given evidence of the senses" (Gregory, 1966)

"Perception creates faces, melodies, works of art, illusions etc. out of the raw material of sensation". (Coon, 1983)

The model is perhaps an obvious one, and as far as creating a game goes, we only need to concern ourselves with visual and aural input (with the tiny exception of force-feedback controllers). This restriction puts extra pressure on the visual and audio aspects of our game, and removes the need for us to create a convincing "smellscape".

It is worth pointing out that impairments to a player's senses can impact a game. At the most basic level, deafness rules out most dialog-heavy games that don't have subtitles, as well as making games in which audio cues form an important part of the gameplay all but impossible. Colorblindness is also a rarely considered, yet significant condition, which can affect a player's enjoyment. Red and green color blindness is the most common form, and while it only occurs in 0.4 percent of the female population, it is estimated to affect eight percent of males, and as gamers are still overwhelmingly male, this figure is not inconsequential. As this form of color blindness restricts the sufferers' ability to differentiate between red and green (hence the name) any vital information in a game that requires color matching (puzzles) or easy identification of colored objects (the baddies are wearing red, the goodies green, for example) could be enough to render the game unplayable.

	FIGURE 2. Colorblindness.