But psychology is passing into a less simple phase. Within a few years what one may call a microscopic psychology has arisen in Germany, carried on by experimental methods, asking of course every moment for introspective data, but eliminating their uncertainty by operating on a large scale and taking statistical means. This method taxes patience to the utmost, and could hardly have arisen in a country whose natives could be bored. Such Germans as Weber, Fechner, Vierordt, and Wundt obviously cannot ; and their success has brought into the field an array of younger experimental psychologists, bent on studying the elements of the mental life, dissecting them out from the gross results in which they are embedded, and as far as possible reducing them to quantitative scales. The simple and open method of attack having done what it can, the method of patience, starving out, and harassing to death is tried ; the Mind must submit to a regular siege, in which minute advantages gained night and day by the forces that hem her in must sum themselves up at last into her overthrow. There is little of the grand style about these new prism, pendulum, and chronograph-philosophers. They mean business, not chivalry. What generous divination, and that superiority in virtue which was thought by Cicero to give a man the best insight into nature, have failed to do, their spying and scraping, their deadly tenacity and almost diabolic cunning, will doubtless some day bring about.

No general description of the methods of experimental psychology would be instructive to one unfamiliar with the instances of their application, so we will waste no words upon the attempt.

To make psychology into experimental epistemology is to attempt to understand the embodiment of mind. Here we are confronted by what seem to be three questions, although they may ultimately be only one. The three exist as categorically disperate desiderata. The first is at the logical level: We lack an adequate, appropriate calculus for triadic relations. The second is the psychological level: We do not know how we generate hypotheses that are natural and simple. The third is that the physiological level: we have no circuit theory for the reticular formation that marshals our abductions. Logically, the problem is far from simple. To be exact, no proposed theory of relations yields a calculus to handle our problem. When I was growing up, only the Aristotelian logic of classes was ever taught, and that badly. The Organon itself contains only a clumsy description of the apagoge - perhaps from the notes of some students who have not understand his master...

This grasping of the whole is obviously the aim of science as well, but it is a goal that necessarily lies very far off because science, whenever possible, proceeds experimentally and in all cases statistically. Experiment, however, consists in asking a definite question which excludes as far as possible anything disturbing and irrelevant. It makes conditions, imposes them on Nature, and in this way forces her to give an answer to a question devised by man. She is prevented from answering out of the fullness of her possibilities since these possibilities are restricted as far as practible. For this purpose there is created in the laboratory a situation which is artificially restricted to the question which compels Nature to give an unequivocal answer. The workings of Nature in her unrestricted wholeness are completely excluded. If we want to know what these workings are, we need a method of inquiry which imposes the fewest possible conditions, or if possible no conditions at all, and then leave Nature to answer out of her fullness.

Only a few years ago one could observe, at least among German psychologists, a quite pessimistic mood. After the initial successes of experimental psychology in its early stages, it seemed to become clearer and clearer that it would remain impossible for experimental method to press on beyond the psychology of perception and memory to such vital problems as those with which psychoanalysis was concerned. Weighty 'philosophical' and 'methodological' considerations seemed to make such an undertaking a priori impossible.

Mere numbers cannot bring out... the intimate essence of the experiment. This conviction comes naturally when one watches a subject at work ... What things can happen! What reflections, what remarks, what feelings, or, on the other hand, what blind automatism, what absence of ideas!... The experimenter judges what may be going on in (the subject’s) mind, and certainly feels difficulty in expressing all the oscillations of a thought in a simple, brutal number, which can have only a deceptive precision. How, in fact, could it sum up what would need several pages of description!

Every one who has seriously investigated a novel question, who has really interrogated Nature with a view to a distinct answer, will bear me out in saying that it requires intense and sustained effort of imagination. The relations of sequence among the phenomena must be seen; they are hidden; they can only be seen mentally; a thousand suggestions rise before the mind, but they are recognised as old suggestions, or as inadequate to reveal what is sought; the experiments by which the problem may be solved have to be imagined; and to imagine a good experiment is as difficult as to invent a good fable, for we must have distinctly present — clear mental vision — the known qualities and relations of all the objects, and must see what will be the effect of introducing some new qualifying agent. If any one thinks this is easy, let him try it: the trial will teach him a lesson respecting the methods of intellectual activity not without its use.

The method of scientific investigation is nothing but the expression of the necessary mode of working of the human mind.

Internal perception also fails as a method for scientific psychology. In the nature of the case, it must be casual and therefore unsystematic. It excludes all deliberate investigation, because as soon as it becomes aware of itself it turns into the self-observation that is open to all the well-known and valid criticisms. It is, indeed, the basis of a psychology of consciousness, in the sense that conscious processes must be perceived to be known, but for a science it is not enough.

The first step in developing a science of any kind of phenomena is to develop and refine instruments that allow one to observe and possibly experiment with the phenomena under investigation. The only instrument we have that enables us to observe mental phenomena directly is the mind itself. But since the time of Aristotle, the West has made little, if any, progress in developing means of refining the mind so that it can be used as a reliable instrument for observing mental events. And… there continues to be considerable resistance against developing any such empirical science even today.

Many are now skeptical of Freud’s theory – and of psychoanalysis in general – but the broad idea that the unconscious is in the driving seat has become widely accepted and has been given empirical support by contemporary research in psychology. Experimental psychologists might be less convinced by the primacy of Freud’s eros and thanatos – the sex and death drives – but they have catalogued a large number of biases and distortions of thought that affect each and every one of us. They may have abandoned Freud’s specific ideas but they have only added to the general picture of human nature he painted in which we are not so much rational as rationalisers, using reason to make sense of our beliefs and actions after the event. Must we therefore accept that reason is a mere veneer for irrational impulses, or can can psychology justify giving rationality an important role in human thought and judgement?

And because this Experimental Science is wholly ignored by the general run of students, for that reason I can not convince people of its utility unless I show at the same time its excellence and its property. This science alone, then, knows how to test perfectly by experience what can be done by nature, what by the industry of art, what by imposture; what the incantations, conjurations, invocations, deprecations, sacrifices (which are magical devices) seek and dream of; and what is done in them, so that all falsity may be removed and that only the truth of art and nature be retained. This science alone teaches one to consider all the insanities of magicians, not that they may be confirmed but that they may be avoided, just as logic considers sophistical argument.

a fairly widespread tendency to report experimental findings with a liberal use of ad hoc explanations for those that didn't "pan out." ... especially tempting in the "soft" fields of (personality and social) psychology, where the profession highly rewards a kind of "cuteness" or "cleverness" in experimental design, such as a hitherto untried method for inducing a desired emotional state, or a particularly "subtle" gimmick for detecting its influence upon behavioral output.

You know how it is when you go to be the subject of a psychology experiment and nobody else shows up and you think maybe that's part of the experiment? I'm like that all the time.

It is only by making physical experiments that we can discover the intimate nature of matter and its potentialities. And it is only by making psychological and moral experiments that we can discover the intimate nature of mind and its potentialities. In the ordinary circumstances of average sensual life these potentialities of the mind remain latent and unmanifested. If we would realize them, we must fulfil certain conditions and obey certain rules, which experience has shown empirically to be valid.