This chapter explores dimensions of the safety problem by considering the complexity of people. The factors contributing to a work injury can be categorized into three areas: Environment factors, Person factors, Behavior factors. The most common reaction to an injury is to correct something about the environment — modify or fix equipment, tools, housekeeping, or an environmental hazard. People take risks on the job because others do the same, and sometimes workers blindly follow a supervisor's orders that could endanger them, other coworkers, or the environment. This reflects the interpersonal power of two principles of social influence — conformity and authority. Donald Norman classifies various types of cognitive failure according to a particular stage of routine thinking and decision making. The four types of cognitive failures are capture, description, loss-of-activation, and mode errors. Unintentional cognitive errors usually occur at the input and output stage of information processing.