A commonly-stated accusation is that psychology is not a 'real science'. Is there any truth to this?
Well, it depends what you mean by science.
ART OR SCIENCE?
University degrees in the UK can be called BSc or BA, depending on whether they are classified as a science or an art. For instance, my degree in English was classified as a BA, because it is considered an art. My degree in psychology was classified as a BSc, because the makers of that course considered it a scientific course.
However, psychology is a bit of a hybrid subject. It is possible to find BAs in psychology in the UK, and even courses which give you the choice to graduate with a BA or a BSc. This betrays an unsureness in the field as to how psychology classifies itself.
Roughly speaking, you might consider psychology an art if you consider that it relies so much on philosophically-derived definitions, that it cannot be said to be a science. For example, if you are a Freudian psychologist, you may not be too concerned as to whether or not you can find objective proof of a concept - it is enough that it seems, to you, to speak truth. In this sense, you are treating truth in a similar fashion to a student of literature, sharing ideas rather subjectively, and taking points of view without resorting to detailed testing.
If, however, you are a psychologist interested in neuroscience, you may be less interested in philosophical nuance, and more interested in using a series of experiments and machines to establish a clear picture of what is going on in a physical thing you call the brain. This is plainly not an art, in the sense that it is not really subjective, but depends on finding objective proof. You don't select a brain scanner because you like its colour, or the humming noise it makes - you select it because it helps you to find an objective truth you think is there in the data.
So there you are - two views of psychology, of the study of the mind. One which sees it as an inevitably subjective interplay and history of ideas (an art); and one which sees it as a quest to map and explain the objective truth of the brain and behaviour (a science).
CAN PSYCHOLOGY BE A SCIENCE?
In a way, the history of psychology is the history of a group of people who desperately want to be taken seriously in the scientific world. Now, if you are equipped with a brain scanner, and are in the business of proving which neurons fire when we perform certain tasks... that has a good chance of being amenable to the 'scientific method' (i.e. proving by testing). But if you are equipped with some pieces of fine literature and a nuanced, philosophical mind... well, you will find it hard to argue your way into being considered scientific, because you are not using official scientific methods.
THE DEVELOPMENT OF SUBJECTIVE EXPERIMENTATION AND LINGUISTIC PSYCHOMETRICS
If you are a psychologist who does not like the idea of using machines, but wants nevertheless to be considered scientific, then you are in luck. Two forms of quasi-scientific pursuit have helped boost the 'philosophicals' into the community of 'scientific method'.
Firstly, what might be called 'subjective experimentation'. For example, you can ask 100 people what they think of something. You then have data about what people think, and can manipulate it much like other test data. A problem with this is that you are assuming that ideas behave in the same way as processes, that concepts can be measured using the same techniques as blood flow.
Secondly, what might be called 'linguistic psychometrics'. You can invent a concept, and then develop a questionnaire which enables you to score people in relation to that concept. For example, you might give new employees a verbal questionnaire designed to categorise them into types of person. You can then score them as high or low in particular attributes, and make judgements about what you are going to do with them. Again, a problem with this is that you are assuming that concepts can be measured in this way; moreover, you are assuming that these types of person exist, and have not been made up by psychologists just to have something to talk about.
All this is good news to the psychologists who do not scan brains. By collecting opinions and ways of thinking, and treating the data as one would a scientific dataset, they can make announcements about what people think, and what they are like, and be believed as though they were scientists.
THE PROBLEM OF CULTURAL PLATFORM
A huge problem with such methods is that they treat the conceptual mind as though it were a 'thing for ever', something unchanging. But the fact is, our concepts drift on the waters of culture. Arguably, proving concepts in humans is much like trying to build houses on moving sands. You can only test a person, in context, at a point in time. Contexts change, times change, concepts even change, and so we can be healthily sceptical of anyone who claims to have categorised humans into types using verbal questionnaires, or claims to have worked out what people think by interviewing them.
SO, IS PSYCHOLOGY A REAL SCIENCE?
I guess one could say that there are certain psychological disciplines, such as neuroscience, whose methods are akin to the 'scientific method'.
But there are other psychological perspectives, involving surveying, gathering or assessing attitudes, which inhabit a less clear region. These areas of psychology are perhaps a science if you consider the ethnographer (the describer of cultural difference) a scientist.
But, according to some, the surveying, gathering, or assessment of atttitude is as much an art as a science. For instance, companies employed to conduct opinion polls will know how much the wording of their questions will influence the results of their research. Politics gets involved, and it can often seem that researchers work hard to get answers they want about concepts they invent. This is science if you allow science to be political. But otherwise, it is perhaps art, a battle of philosophies, an attempt to build houses on sand.
In summary, perhaps psychology, more than any other discipline, finds itself embattled as to what it is, and what its methods are. It often tries to use the methods of science (prolific referencing, statistical technique) to bolster the appearance of science. But it is perhaps over-prone to use such methods where they may not fit: in the territory of ideology and deep concept, where its management and manipulation can start to look much more like an art.
The above article uses a somewhat clumsy, but prevalent, definition of a science, as something which follows traditional scientific method. But one could argue that, culturally, we have created a false duality between sciences and arts, and that what we have is a continuum of understanding ranging from the statistical/informative at one end, to the expressive/conformative at the other. I've been deliberately lazy about this, in an attempt to make the discussion practical. Sorry.