Competition and specificity. This figure shows how signalling specificity may be improved by competition effects. It considers the case of two switches which are regulated by the same upstream component. Each of the switches in isolation display switching behaviour at the same input dosage. a) shows the response of the switches in isolation, and b) shows the switches operating together. It is clear that it is not possible to choose input values for the isolated case which would result in mutual specificity. However, when they operate together mutual specificity can be obtained by having low inputs activating A and high inputs activating B, triggering the relevant switch.