must be taken by court and jury on his authority; it could not be expected of the court, still less of the jury, that it should examine into the soundness of the methods which he had employed. Yet it must be plain from what has been pointed out above that, even assuming—which is a great deal—the possibility of expending the necessary amount of time and pains upon the inquiry, none but the most highly qualified expert could be safely entrusted with it. Professor Münsterberg is a man not only of the highest professional training, but of extraordinary native powers of mind; yet he not only makes a fundamental error in one instance, but in a number of others overlooks elements essential to the true bearing of the facts upon the question in hand. In addition to the points already noted, one other may be mentioned which throws perhaps an even stronger light on the pitfalls that lie on all sides. It is a curious circumstance that in none of the questions put by Professor Münsterberg to his class does he give any room (or at least any encouragement) to the simple answer, "I don't know." How many of the queer guesses he got in response to the question as to what caused the sound he made by striking the hidden tuning-fork would have been choked off by the simple and straightforward plan of telling the students to answer only in case they felt a reasonable assurance, there is no means of telling. And yet in court a truthful witness would do that very thing. If he had heard a sound the character of which he could not identify, he would so state to the court, and not say it was a bell or a church organ or a human song or what not. A man who, upon being asked to make the best guess he can, makes a very bad guess is not necessarily an unreliable witness; he may be the very man who on the witness stand would refuse to testify to things that he doesn't feel sure of, and who, when he does make a statement, may be implicitly believed. And the same remark applies, in some measure, to nearly all the tests in Professor Münsterberg's questionary. If Professor Münsterberg has laid himself open to criticism in so many points, how much less would it be possible to entrust to an every-day psychologist the decision of so delicate a question as that of the degree of reliability of each of the witnesses in a given case?
There is one very striking test, of a different character from any of the others, to which I have made no reference, and which might be pointed to as concrete proof of the correctness of the method in spite of any criticism that may be brought against it in the abstract. This is an experiment in which Professor Münsterberg, having asked his class to describe everything that he was going to do from one signal to another, did certain conspicuous things with his right hand, upon which he ostentatiously fixed his own attention, while at the same time he did a number of other things with his left hand. The result was that 18 out of 100 students were utterly unaware that he was doing