{"agent_id":"sully","agent_name":"James Sully","slug":"the-psychology-of-illusion","label":"The psychology of illusion: is error continuous with normal cognition and revealing of it?","topic":"The psychology of illusion","question":"Is error continuous with normal cognition and revealing of it?","position":"There is a common prejudice that illusion is a mere defect, an accident of a mind gone momentarily wrong, of no interest to the student of its sound working. I hold the contrary: that illusion is one of the surest windows into the normal mind. The illusions of sense, of memory, of belief, of introspection itself are not produced by some special faculty of error; they are produced by the very same processes — the associations, the expectations, the swift unnoticed inferences — that in ordinary circumstances give us truth. The eye that is deceived by the bent stick in water is the eye that ordinarily sees truly, following the same habits of interpretation; the memory that misremembers is the memory that ordinarily recalls, betrayed by the same reconstructive tendency. To study where and how the mind goes wrong is therefore to catch its machinery working in the open, its ordinary operations thrown into relief by their failure. Error is continuous with knowledge, and the psychology of illusion is the psychology of the normal mind read by the light of its mistakes.","paragraphs":[[{"t":"There is a common prejudice that illusion is a mere defect, an accident of a mind gone momentarily wrong, of no interest to the student of its sound working.","n":[]},{"t":"I hold the contrary: that illusion is one of the surest windows into the normal mind.","n":[]},{"t":"The illusions of sense, of memory, of belief, of introspection itself are not produced by some special faculty of error; they are produced by the very same processes — the associations, the expectations, the swift unnoticed inferences — that in ordinary circumstances give us truth.","n":[1,2]}],[{"t":"The eye that is deceived by the bent stick in water is the eye that ordinarily sees truly, following the same habits of interpretation; the memory that misremembers is the memory that ordinarily recalls, betrayed by the same reconstructive tendency.","n":[]},{"t":"To study where and how the mind goes wrong is therefore to catch its machinery working in the open, its ordinary operations thrown into relief by their failure.","n":[]}],[{"t":"Error is continuous with knowledge, and the psychology of illusion is the psychology of the normal mind read by the light of its mistakes.","n":[3,4,5]}]],"texts":"Illusions: A Psychological Study (1881). Reception: the durable strategy of studying normal function through its breakdowns (the perceptual-illusion literature, the cognitive-bias tradition from Kahneman and Tversky, the neuropsychology of deficit); the modern understanding of illusions as products of the visual system's inferential and Bayesian machinery.","works":["Illusions: A Psychological Study (1881)"],"reception":"the durable strategy of studying normal function through its breakdowns (the perceptual-illusion literature, the cognitive-bias tradition from Kahneman and Tversky, the neuropsychology of deficit); the modern understanding of illusions as products of the visual system's inferential and Bayesian machinery.","status":"This is Sully's most original and most durable idea. The strategy of studying normal mental function through its systematic breakdowns and errors became one of psychology's most productive methods: perceptual illusions as evidence of the visual system's inferential machinery; the cognitive-bias program of Kahneman and Tversky, which reads the mind's judgment heuristics off its systematic errors; neuropsychology's use of deficits to map normal function. The modern account of illusions as products of the perceptual system's inferential, expectation-driven (Bayesian) processing is precisely Sully's thesis — that the same machinery which usually yields truth yields the illusion under revealing conditions — given a rigorous mechanism. Here Sully anticipated a permanent feature of the science.","era":"1842-1923","discipline":"Psychology","refs":[{"n":1,"work":"Illusions A Psychological Study","page":"","canonical":"","quote":"At the same time, it is to be remembered that this division is only a very rough one. As will appear in the course of our investigation, the same error may be called either a fallacy or an illusion, according as we are thinking of its original mode of production or of the form which it finally assumes; and a thorough-going psychological analysis of error may discover that these two classes are at bottom very…","label":"Illusions A Psychological Study"},{"n":2,"work":"Illusions A Psychological Study","page":"","canonical":"","quote":"A little consideration, however, will show that this is not an adequate definition of what is ordinarily understood by an illusion of sense. There are special circumstances which are fitted to excite a momentary illusion in all minds. The optical illusions due to the reflection and refraction of light are not peculiar to the individual, but arise in all minds under precisely similar external conditions.","label":"Illusions A Psychological Study"},{"n":3,"work":"Illusions A Psychological Study","page":"","canonical":"","quote":"At the same time, popular usage lias long since extended the term so as to include under it errors which do not counterfeit actual perceptions.","label":"Illusions A Psychological Study"},{"n":4,"work":"Illusions A Psychological Study","page":"","canonical":"","quote":"On its objective side, reasoning may be 1 I sav \" -usually,\" because, as wc have seen, there may sometimes be a permanent and even an inherited predisposition to active illusion in the individual temperament and nervous organization. ILLUSION AND FALLACY. 335 roughly defined as a conscious transition of mind from certain facts or relations of facts to other facts or relations recognized as similar.","label":"Illusions A Psychological Study"},{"n":5,"work":"Illusions A Psychological Study","page":"","canonical":"","quote":"This being so, we may very roughly describe all illusion as abnormal. Just as hallucination, the most signal instance of illusion, is distinctly on the border-land of healthy and unhealthy mental life; just as dreams are in the direction of such unhealthy ERBOR AS INDIVIDUAL.","label":"Illusions A Psychological Study"}],"answer":null,"siblings":[{"slug":"associationism","label":"Associationism: is the mind built up from elementary sensations by the laws of association?"},{"slug":"child-study","label":"Child study: is the systematic observation of children a proper method and the key to mind and education?"},{"slug":"the-comic","label":"The comic: is laughter to be explained by a natural psychology of play and incongruity?"},{"slug":"pessimism","label":"Pessimism: does philosophical pessimism survive a sober empirical psychology of pleasure and pain?"}]}