NumericalDecision Processing causing stock price clustering?

The stock price clustering phenomenon has been studied in the context of numerical perception and response. The numerical response process of the theory of prominence models how persons generate numerical responses if they have diffuse numerical information (know a range of reasonable alternatives). These predictions are compared with empirical data (the inside quotes of 30 stocks traded on the IBIS computer exchange in March/April 1993). The numerical response process predicts the principal structure of the data. A similarity was observed between the quotes and a laboratory experiment in which the diffuse numerical information has been controlled.