The feedback arrow extending from the response to the distal state in the lens model, together with Brunswik's dictum that the organism is a stabiliser of systems, implies a dynamic view of behaviour. This paper describes the main problems in the study of dynamic decision making: feedback delays and the feedback structure of the tasks. It also describes microworlds, a methodology for studying dynamic decision making in the laboratory. The results from experiments with microworlds show that subjects have problems compensating (...) for feedback delays and side effects. These results are discussed in terms of Brunswik's distinction between perception and thinking. (shrink)