Fun on the whole is a pretty amorphous concept and being reasonable about it is tricky, however there are some routes of enquiry.
My personal understanding of fun comes from the experience of programming gameplay mechanics (such as character control, AI and minigames) and through designing and pitching games professionally. This has led me to create a number of theories about why games (and other forms of entertainment) are fun.
These ideas are built on my experiences of adjusting games and game pitches to make them more enjoyable. On the whole this sense of enjoyment is based on the opinions of those making (or paying for the development of) the games (where groupthink is a problem). However, many of the games and their pitches have been evaluated by focus groups and gameplay recordings, performed in relatively controlled settings. Additional information comes from finding patterns in sales figures and other representations of what people enjoy (e.g. the types of magazine available for sale in newsagents).
From these experiences I've attempted to find simple theoretical justifications for the behaviour I've observed. In some cases, these theories have some validation through external research, but on the whole are not experimentally validated. I take the view that it is better to have some sort of theory rather than nothing, and indeed these theories have been very useful in guiding my work.
These ideas will focus on the fun (or more generally the source of motivation) provided by computer games however I believe there are many generalities that can be made from them.
When thinking about the experience of a game I find it useful to break the game experience into 4 distinct stages:
To keep the article short I've decided to split these stages up over multiple articles, hopefully there is enough meat in each to be interesting.
Attraction is the first step in obtaining enjoyment from a game or other form of entertainment. In particular, if a game box is not interesting enough to pick up then the sales are likely to be low. At least one games studio measures this explicitly with a mock up of an actual store containing both existing and potential game titles. If a set of test customers fail to look at or purchase a proposed game then it is not developed further.
One of the most signficant factors affecting the attractiveness of a product is a customer's cultural identity. Looking at toy bestsellers, there is a trend to have the stages of child development mirrored in the most popular entertainment. In particular, toys pass from amorphous learning tools (bright objects and blobby humanoids), through mimicking parents (accurate baby dolls), to mimicking older children (sexualised dolls and makeup). In this way toys become a tool for children to reinforce their sense of appropriate behaviour and appearance.
Once a child is socialising, this experience is enhanced by group consensus on what is popular, an approach that can continue through adulthood. This is heavily exploited by those selling entertainment aimed at children and indeed licenced games (disney, pixar etc.) are the most lucrative for the younger demographic. It should also be noted, however, that this data is skewed by the fact that the purchasers (parents, family friends) will only know of the big brands.
For older children and adults this sense of reinforcing culturally validated behaviour remains extremely strong. One of the main challenges facing a games designer is to identify a theme or form of presentation that a customer will view as being designed 'for them'. Many of the recent big financial successes in games have come from expanding into demographics where game playing is considered taboo or inaccessible (for example, Deer Hunter, the Sims, SingStar, WiiSports, Braintraining). Customers for these forms of entertainment will often refer to the titles as being 'not a game' in order to diminish the negative associations of the medium. This behaviour is also found in those who view games playing as part of their identity. Such people can experience significant anger and disdain towards titles that weaken this association.
Much of this categorisation does not seem to be innate, for example girls who have grown up in households where they have access to a game console passed down from older brothers tend to have much lower cultural barriers to playing computer games than those who have not. Likewise, once an appropriate format has been found, even adult players can begin to take enjoyment from previously taboo titles.
Cultural appropriateness is most easily achieved by mimicking existing popular products, but doing so will significantly reduce the sales of a title, with customers viewing a product as a cheap imitation, even if the mechanics and production quality remain very similar to the original. Although this feels obvious, the reasons behind it are not so clear, if games are intrinsically motivating why does it matter whether they are novel, good food tends to be good food regardless of who cooks it. However, this combination of relevance and distinctiveness does seem to reappear in many forms. For example, most types of entertainment are advertised using a picture of a face. Studies of perceived facial beauty show that average shaped faces are considered more beautiful, with many beauty pageant winners having these kind of faces. However, these average faces can appear bland and generic. Film stars, in contrast, tend to have distinctive faces which, if adjusted slightly, will tend to look ugly. This distinctiveness can also be seen in the appearance of successful rock bands or computer game characters that can be identified even when reduced to icon sized pixel art.
To me, this attraction reflects a fundamental element in our mental processing. In effect we are continuously modelling the world and forming classifications. This classification process is intrinsically motivating and is independent of any survival benefit that any particular classification provides. This results in a positive feeling when we encounter things that are consistent with our models (relevant) particularly if they are unlike our other experiences (distinctive). This is especially pronounced when our sense of identity and community are the subject of the classification. This flexible self organising behaviour provides a great survival benefit, enabling us to adapt to new environments and adopt novel social structures. In particular, this enables us to partition into different groups adopting distinct specialised roles exploiting complementary opportunities. Such motivations may have evolved from our need to identify what is and is not safe to eat, explaining why we associate disgust and good taste with taboo and appealing things ("good enough to eat") respectively. This, in turn, provides a rationale for the strong feelings we have about seemingly irrational values and actions (religion, fashions, politics). Implying that, in our evolved environment, the strong motivation to form common patterns of behaviour may convey a greater aggregate survival benefit than the actions of a community of independent reasoning agents.