When we follow the way of the psychologist, we recognize that software defects are the result of human error. Human error has relatively recently become an area of study for cognitive psychologists.
There are two major contributing factors in the study of human error by psychologists. First, in the 1970s and 1980s, a number of cognitive psychologists developed information-processing models of human intelligence. These models have many common or similar features. They provide sufficient detail about how the human mind seems to work that they have enabled psychologists to explain many types of observed human error.
The second contributing factor to the development of the study of human error is the proliferation of highly complex automated systems: nuclear power plants, jet airliners, medical devices, and so forth. All have the power to do great good, but they also have the power to cause great harm, including loss of property and life, because of human failures in design or in operation.