A few months ago, I read Edmund Husserls' Ideas, the work that launched the field of phenomenology. It is also the single most dense and confusing book I have ever read. I am in the habit of reading books from this school of philosophy, and while they are often obtuse, this is steps beyond any others that I have read.
However, I did get a few ideas from the book, one of which is the consistent and insistent declaration by Husserl that phenomenology, meant to be the study of how ideas form in the mind, is not a form of psychology. This seems to be a statement that needs some explaining, since the way that ideas appear and develop in the mind would seem to be the province of psychology.
Part of the reason may be historical. At the time that Husserl was writing (the work was published in 1913), "psychology" would usually mean Freudian psychology, with its basic belief in sexual complexes and all the other dressings of a rather convoluted Turn-of-the-Century mindset. Given that Husserl's examples of mental processes tend towards the abstract, the difference between Freudian psychology and Husserl's phenomenology are obvious.
Although, we live almost a hundred years later, when psychology has spread both in its theory, and in the amount of empirical evidence to back it up. Can we imagine that Husserl might be more comfortable equating phenomenology and psychology today? While it may be so, I also believe that there is a basic distinction that must be drawn.
We can look at our mind as both an entity and a capacity. Our mind as an entity is the product of our biographies, and has what we might think of as our substance: our desires, aversions, memories, self-image and many other facets of selfhood. On the other hand, our mind as capacity is the ability of the mind to perceive, understand and think without reference to a specific being doing these activities. If we take "psychology" to mean the study of mind as entity, Husserl's concepts are not a psychology. If, however, we take "psychology" to mean the study of mind as capacity, than Husserl's concepts are very much a psychology. That, at least, is my first and naive take on the matter.
Of course, the question of whether the division between our mind as entity, and our mind as capacity, could actually be made on a practical level, is a very large question, and seems to be one of the main questions that Husserl's student, Jean-Paul Sartre, tackled in Being and Nothingness.