  We present results on simulations of a stock market with heterogeneous,
cumulative information setup. We find a non-monotonic behaviour of traders'
returns as a function of their information level. Particularly, the average
informed agents underperform random traders; only the most informed agents are
able to beat the market. We also study the effect of a strategy updating
mechanism, when traders have the possibility of using other pieces of
information than the fundamental value. These results corroborate the latter
ones: it is only for the most informed player that it is rewarding to stay
fundamentalist. The simulations reproduce some stylized facts of tick-by-tick
stock-exchange data and globally show informational efficiency.
