  The unprecedented access offered by the World Wide Web brings with it the
potential to gather huge amounts of data on human activities. Here we exploit
this by using a toy model of financial markets, the Minority Game (MG), to
investigate human speculative trading behaviour and information capacity.
Hundreds of individuals have played a total of tens of thousands of game turns
against computer-controlled agents in the Web-based_Interactive Minority Game_.
The analytical understanding of the MG permits fine-tuning of the market
situations encountered, allowing for investigation of human behaviour in a
variety of controlled environments. In particular, our results indicate a
transition in players' decision-making, as the markets become more difficult,
between deductive behaviour making use of short-term trends in the market, and
highly repetitive behaviour that ignores entirely the market history, yet
outperforms random decision-making.
  PACS: 02.50.Le; 89.65.Gh; 89.70.+c
  Keywords: Decision theory and game theory; Economics and financial markets;
Information theory
