The Mechanisms of Perception

Jean Piaget

• Publisher: Routledge
• Year: 2013
• eBook ISBN: 9781135660154
• Edition: 1
• Topic: Psychology
• Subtopic: Developmental Psychology
• Index: Psychology

First published in 2006. This work represents an attempt to synthesise studies on the development of perception which Piaget started twenty or so years ago, when the Faculte des Sciences de Geneve appointed him to the Chair of Experimental Psychology and Director of the Psychological Laboratory. Most of the studies to be reported have already appeared in the Archives de Psychologie under the general title of Recherches sur Ie Developpement des Perceptions, however, more than fifteen studies which have not been published and which we shall deal with in the following pages.

Part One
Primary Effects

No genetic significance will be attributed to the term 'primary' which might imply an origin necessarily anterior to those perceptual activities to be studied in Part Two. The designation refers only to the greater simplicity of the responses involved: at a given genetic level those perceptual effects which occur in one and the same momentary field of centration will be called primary. The criterion is the possibility of obtaining such effects in tachistoscopic presentations of the stimuli, namely under conditions which prevent visual explorations, transportation by means of displacements of fixation, etc. We need not decide at this stage whether these effects (which are also called 'field effects', but with reference only to the simple field of centration and without suggesting analogies with 'fields' in the physical sense of the term) are anterior to all perceptual activity and result from elements simultaneously perceived in a single perceptual field, or whether they constitute the crystallised product or 'sedimentation' of previous perceptual activities. This problem will be discussed at the end of Chapter III. Similarly, the question of whether the number and extent of primary effects increases or diminishes with age may be postponed: at this stage we will merely describe them and attempt to explain them in terms only of the mechanisms of centration.

I Primary Illusions and the Law of Relative Centrations

The illusions referred to as primary correspond to most of the optico-geometric illusions. Among them are: the illusions of rectangles (the over-estimation of the longer side); the T figure (to the extent that it introduces semi-rectangles, the over-estimation of the vertical as such being actually 'secondary'); the over-estimation of a segment of a straight line either when extended by a smaller segment or when inserted between two smaller segments; the Delbœuf illusions (of concentric circles); the illusions of angles (the over-estimation of acute and the under-estimation of obtuse angles, and the illusions of the arms of angles); the illusions of lozenges (the under-estimation of the longer diagonal); the Müller-Lyer illusions; illusions of parallelograms; of curvature, etc., and finally, marking the transition to secondary illusions, the Oppel-Kundt illusion of divided spaces.

The aim of this chapter is to try to reduce ail these perceptual illusions, or deformations, to a single law by reducing each of them to certain constant relations which entail an over-estimation of the greater of two compared segments and an under-estimation of the smaller. The explanation of the law itself, and of the principle of these over- and under-estimations, will be reserved for the next chapter.

§ 1. The Status of the Problem

The primary illusions have two fundamental characteristics. The first is that their qualitative characteristics (the location of the positive and negative spatial maxima and of the median zero illusion, in relation to the proportions of the figure) do not change with age, while their absolute quantitative values, the extent of illusion, usually diminish, occasionally remain constant, but do not increase with age. The second characteristic, on a par, no doubt, with their qualitative invariance at all ages, is that they occur even in tachistoscopic presentations which are so short as to exclude ocular movements and consequently secondary activities of exploration, transportation, etc. These primary illusions can therefore be considered to result from simple field effects, that is to say from the quasi-simultaneous interaction of elements perceived together in one single field of centration without the involvement of a displacement of fixation. They are called 'primary' for this reason, but this in no way prejudges their physiological status. Binet called them 'innate', which involves an unnecessary hypothesis because they could result from general, but still not hereditary, simple equilibrating mechanisms (see Chapter II).

Thus described, the primary illusions constitute the most elementary perceptual phenomena with which we shall be concerned. We can conveniently open our analysis with their examination which immediately raises a major problem: do the primary illusions (which are classical examples of the deforming nature of events occurring in space perception and yet only involve the simplest and most rational of figural relations) obey a general law which reveals something of the nature of deformations which may be consubstantial with perception?

Strangely enough, no one, since the first studies of optico-geometric illusions were made over a century ago, has undertaken the task of discovering such a common law. Until the recent studies of Motokawa on retinal induction, investigators have limited themselves to a series of qualitative and disparate explanations. Woodworth, in his excellent text on psychology, challenged psychologists to extract from the illusions some general relations which would lead to predictions. We, while remaining on purely relational territory, have attempted to meet this challenge, not from an ambition to re-examine this repeatedly discussed problem for its own sake, but from an interest in the general problem of perceptual deformation, an interest which has involved us in the search for a law.

Why has so little thought been given to this problem? No doubt psychophysics was too ambitious in wanting to measure sensations directly, as if they constituted the absolute elements out of which perception could be reconstructed by a form of atomic composition. Psychophysics thus ran into the problem of 'systematic errors' of all sorts (spatial, temporal, etc.), which were regarded simply as obstacles standing in the way of those absolute measurements which were considered to be the ideal to be pursued. In time, however, particularly after the formulation of Gestalt theory, error ceased to be regarded as a troublesome obstacle and came to be regarded as a proper object of study. This was not only because of its ubiquitous nature, but because it exhibits that immediate interaction whose equilibrium, in terms of the totality of the field, finds expression in perception. But the theory of form then took a paradoxical course in trying to explain, by the same principle of the whole, both good forms (circles, squares, etc.), in which deformations are precisely minimal, and illusions, which were invoked to illustrate the subordination of the parts to the whole. Deformations were considered from this particular point of view only, which was insufficiently ambitious, and led Gestalt theory to substitute a simple qualitative description for measurement (which does not mean, of course, that Gestaltists have not measured a large number of the effects of deformation, but they have only drawn a justification of the laws of organisation from these measurements and not a mathematical expressio...

Table of contents

• Cover
• Title
• Copyright
• Contents
• Author's Preface
• Translator's Preface
• Foreword
• Introduction
• PART ONE: PRIMARY EFFECTS
• PART TWO: PERCEPTUAL ACTIVITIES
• PART THREE: STRUCTURES OF PERCEPTION AND OF INTELLIGENCE
• Appendix
• List of Recherches
• Index