  The speculation game is an agent-based toy model to investigate the dynamics
of the financial market. Our model has achieved the reproduction of 10 of the
well-known stylized facts for financial time series. However, there is also a
divergence from the behavior of real market. The market price of the model
tends to be anti-persistent to the initial price, resulting in the quite small
value of Hurst exponent of price change. To overcome this problem, we extend
the speculation game by introducing a perturbative part to the price change
with the consideration of other effects besides pure speculative behaviors.
