As language learning is a question of developing quick reflexes, how else can this be done than by a system of stimulus and response?

The same psychologist went on to take an exaggerated example, by adding that one could teach a monkey to play the piano, given such techniques. In other words the monkey, like a pianist, a typist or a language student, is learning to perform a trick, and tricks are best learnt through practice and through a system of stimulus and response, which in the case of the Callan Method means quick-fire questions and answers. The difference between the monkey and the pianist, typist and language student, however, is that the monkey cannot do much with the trick he has learnt, whereas the pianist, typist and language student can; for them the trick is a means to an end. For the monkey it is an end in itself.

Not answering questions
We are not teaching people to answer questions, but to make full sentences, practise target lexis and structure in a controlled way. We aim to develop accuracy, fluency, and the ability to understand and think in English.

It's too easy;  therefore, it cannot be any good
Although the Callan Method looks very simple, and is very easy to operate, it is far more complex than it appears. To arrive at such apparent simplicity took fifteen years of intensive research and experimentation.
Learning anything is usually associated with hard work. Many people feel that the more one sweats the more one is learning - no pain, no gain. If the Callan Method is simple and easy and requires little effort on the part of the student, it must be viewed with suspicion. Such people find it difficult to believe that anything that has been so difficult over the centuries should suddenly become easy.

The Method does not teach just conversation
Because the Callan Method teaches English through a process of quick-fire questions and answers, it gives the student the impression that it just teaches conversation and not the other aspects of the language. Like so many other things that people conclude about the Method, this is totally untrue. The Method teaches the student all the grammar and how to write to the level of the Cambridge First Certificate. Because it teaches these things through easy conversation it appears that it does not teach them at all: it seems all too easy – and yet, as if by magic, the student passes the Cambridge exams.