Not that long ago, I suggested that studying the size of brain regions would be a valuable way of exploring the neurobiology of play, a conclusion I reached after learning that one of the hippocampi of taxi drivers is bigger than those of a control group. And this research, I'm pleased to say, is taking place. Via Raph Koster (thanks Raph!), I learned today of a new study exploring the size of the nucleus accumbens (pleasure centre) and two key structures in the striatum (the limbic system's link to the decision centre) - two of several brain features I'm interested in.

The research is by Art Kramer (pictured above, left) at Illinois, Ann Graybiel of MIT (centre), and Kirk Erickson of the University of Pittsburgh (right). The short form of their findings is as follows:

• Players with a larger pleasure centre (nucleus accumbens) did better in the early stages of the study i.e. began learning more quickly. This suggests that a large pleasure centre increases motivation to perform (an expected result).
• Players with a larger caudate nucleus and putamen, two key features of the striatum (the limbic system-end of the decision centre) performed better at variable priority training i.e. practising and learning different skills dynamically, within the framework of the overall goal. (This is also an expected result, but is less well studied).

The striatum is beginning to emerge as a key part of adaptation in learning. Whereas both the pleasure centre and the striatum are involved in learning, the former drives habit formation, while the latter seems to be more involved in adaptability and dynamic response. Furthermore, the striatum appears to be directly involved in executive function (i.e. it links to the orbito-frontal cortex - the decision centre). There is much less research on the latter than the former, which is one of the reasons this new study is particularly interesting.

This research requires me to make a slight change in my hypothetical research programme - I had been thinking in terms of a bigger decision centre (orbitofrontal cortex) for strategically minded players, but this could be hard to detect. The striatum, which links the decision centre to the limbic system (the "reptile brain"), is a more obvious place to look for changes in volume. Now I can confidently predict that people who test Rational on Temperament-style personality tests, university science students, and players who enjoy complex strategy games, will show a statistical prevalence for dorsal striatum that are larger than the mean size. (And also, that those three groupings I cite will cross-correlate reasonably well).

Unsurprisingly, this new research supports the "games as learning" model because the focus of this study are the brain centres involved in the dopamine/learning system. However, it would be premature to use this as evidence that learning will provide a complete theory of play or fun - I believe it is already clear that it cannot, since Biederman and Vessel's research on interest and curiosity is memory-focused, not learning focussed (although still links to the pleasure centre). Furthermore, there is still little or no neuroscience providing for a model of imagination, and without this (and more besides!) there can be no complete theory of games. What we can be confident of - and what Koster correctly predicted - is that any complete theory of games and fun must feature learning as a key part of the story. What the new research does suggest is that learning may be more important in the play of people with larger dorsal striatum - such as the three groupings I suggested above.

However, we should be careful of jumping to the assumption that what is implied here in terms of differences in brain structure sizes is wholly genetic - it certainly wasn't in the case of taxi drivers, and I doubt it is here. Genetics and environment probably both have a role, but the taxi driver study suggests what we do is more important than our genetic blueprint when it comes to the size of brain regions. I find this aspect of the current brain research to be encouraging, as it maintains an important role for the self in discovering and inventing who we shall become.