What is the stimulus error?

Edward Bradford Titchener, answered from the texts and cited to the page.

Edward Bradford Titchener answers

The stimulus error is the cardinal sin of introspective observation, and understanding it is the first condition of doing psychology at all. When an observer is set to examine a conscious process — a sensation, a perception, the experience of a tone or a taste — the natural and overwhelming temptation is to report not what is given in consciousness but what the stimulus is, what the thing is, what the experience is about.

The observer says "I see a book," "I hear a loud noise," "I taste something sour." But none of that is psychology. That is a report on the object, the physical event, the external referent — not on the bare conscious content itself. The stimulus-error is precisely this substitution: reporting the thing perceived in place of the perception.¹ It is, as I have noted, both insidious and persistent.

One could compile a long list of warnings against it issued by psychologists who then fell into it themselves.² The error is natural because it is customary to think of things and events about us rather than of mental processes; and it is dangerous because it is so difficult to catch oneself committing it. The remedy is long training — the kind of disciplined practice that teaches the observer to attend to the grey, not the grey paper; to the kinaesthetic sensation, not the weight; to the visual magnitude, not the size of the object.³

The error is not confined to the study of sensation. It reappears, in a subtler form, wherever introspection is insufficiently guarded — and this is precisely my charge against the Würzburg method. When Bühler's observers reported a "peculiar stage of reflection," a "tendency to accept the statement," a thought about Spencer's criticism of altruism, they were not describing what their consciousness was — they were reporting what it was about.⁴

They told us the reference of consciousness to things and words rather than photographing consciousness itself; they committed, in the domain of thought, the very error we name the stimulus-error in the domain of sensation.⁵ The stimulus-error can sometimes be ruled out by the observer's ignorance of the conditions producing the experience, but in general it can be overcome only by exactly that long training which the Würzburg procedure conspicuously lacked.⁶

A method that notes experiences and leaves them without further attempt at analysis — that simply collates reports and classifies what they mention under headings like "awareness" or "thought" — is a suggestive method, not a scientific one.⁷ Until the method is refined to the standard that research in sensation has shown necessary, the charge of an error akin to the stimulus-error stands on more than personal impression.

Sources

1. it is, as I believe, absolutely necessary to get rid of things, and to think only of the mental processes, if we are to have a science of psychology.

   Lectures on the Experimental Psychology of the Thought-Processes

2. The error is both insidious and persistent; I could quote you a long list of warnings to avoid it; and I could show you that those who give the warnings do not always themselves escape the error.

   Lectures on the Experimental Psychology of the Thought-Processes

3. he will concern himself not with greys but with grey papers, not with kinaesthetic sensations but with weights, not with visual magnitude but with the size of objects.

   Lectures on the Experimental Psychology of the Thought-Processes

4. the observer is not describing his thought, but reporting what his thought is about; not photographing consciousness, but formulating the reference of consciousness to things and words.

   Lectures on the Experimental Psychology of the Thought-Processes

5. has fallen, in the case of thought, into the error which we should term the stimulus-error in the case of sensation.

   Lectures on the Experimental Psychology of the Thought-Processes

6. In some cases, the stimulus-error is ruled out by the observer's ignorance of the conditions under which the mental process laid before him for analysis is produced; in general, however, it can be overcome only by long training.

   A Text-book of Psychology

7. The introspective reports have simply been collated, and the processes which they mention classified, under general headings, as ideas, feelings, attitudes, and processes that are termed sometimes awareness, sometimes knowledge, sometimes 'the consciousness that…,' most frequently thoughts.

   A Text-book of Psychology