Recent studies have provided evidence for mental simulation as a strategy in mechanical reasoning. This type of reasoning can be dissociated from reasoning based on descriptive knowledge in that it depends on different abilities and memory stores, is expressed more easily in gesture than in language, exhibits analog properties, and can result in correct inferences in situations where people do not have correct descriptive knowledge. Although it is frequently accompanied by imagery, mental simulation is not a process of inspecting a holistic visual image in the 'mind's eye'. Mental simulations are constructed piecemeal, include representations of non-visible properties and can be used in conjunction with non-imagery processes, such as task decomposition and rule-based reasoning.