Well-designed interfaces use procedural and sensory cues to increase the salience of appropriate actions and intentions. However, empirical studies suggest that cognitive load can influence the strength of procedural and sensory cues. We formalise the relationship between salience and cognitive load revealed by empirical add these rules to our abstract cognitive architecture developed for the verification of usability properties. The interface of a fire engine despatch task used in the empirical studies is then formally verified to validate the salience and load rules. Finally, we discuss how our formal modelling and verification suggest further refinements of the rules derived from the informal analysis of empirical data.