Before revision:  (ii) the most direct stochastic extension of Hull model, characterized by the presence of stochastic noise; (iii) a theory where response fluctuations are described by quantum mechanics and based on the general framework of dynamical models (i) explaining the noise met in (ii) and giving characteristic predictions .
After revision:  (ii) the theory can be further extended to describe response fluctuations by the laws of quantum mechanics. (iii) We also introduce an independent model characterized by the presence of a stochastic noise of cognitive origin .