Modelling an artificial stock market: When cognitive institutions influence market dynamics

The paper presents an artificial financial market designed to analyse market dynamics from the behaviour of investors. The model especially allows highlighting the role of a particular kind of institution in the orientation of market dynamics. The information – delivered by financial intermediaries as rating agencies and considered as a cognitive institution – directs the decisions of investors who are heterogeneous agents endowed with capabilities of learning in a changing environment. We demonstrate that the cognitive institution influences market dynamics as it allows the co-ordination of the decisions of investment in the same direction. The information delivered by rating agencies is clearly a « focal point » for investors and contributes to generate a speculative dynamic on the market.