One of the more difficult problems confronting software engineers today is the construction of accurate predictive models of the software development process, [2],[8] and [9]. It has long been recognized that one of the most essential elements of any successful model of this process is a quantification of the complexity of software systems. During the past several years a great deal of work has been performed by researchers such as Halstead [3], McCab [5], and others in an attempt to develop metrics which adequately capture the complexity of software systems. Yet one very important aspect of software development complexity seems to have been overlooked in the rush to develop software complexity metrics, q.e. it's psychological nature.