The Concomitant Variation of Stimuli and the Phenomenal Structures in Michotte

The experimental phenomenology of Michotte (1962; Thines, 1991: 15) shows that avoiding the stimulus error does not imply rejecting the concept of stim­ulus in experimental practice. Rather it is treated as a theoretical construct that denotes the controlled conditions that are varied to observe when and how the phenomenal structures systematically arise, which features they have and which factors or rules account for them. This research still requires that the denotation of common-sense beliefs and scientific knowledge is sus­pended. Therefore, the experiments aim at disentangling the independent structures and rules of perception from psychic functions, associations and habits. Michotte (1962) holds that as the world of physics is revealed by mea­surement instruments, so the phenomenal world, that is to say the world of things just as they appear to subjects, is revealed by the descriptions con­tained in observers’ reports that are systematically coupled with stimulation in controlled conditions. In comparison with physical measures, what the subjects perceive with a given stimulation is considered an inaccessible un­known. Yet it is possible to ascertain that the descriptions match satisfactorily the corresponding situation which, according to the subjects’ beliefs, takes place outside their mind.

Michotte (1936: 216-217) argued that subjects’ verbal reports could be re­garded as “differential reactives” (reactif differential), like the motion of the pointer of the galvanometer, in the sense that they allow one to determine whether different subjects perceive the same X or not given well-defined stim­ulation conditions, regardless of what X looks like to each of them. Suppose a set of moving dots is presented to the subjects, who agree in reporting seeing “a group of dots among which those at the right form a pentagonal figure.” This report is not sufficient to tell that different subjects have had the same visual impression, since it is still conceivable that they utter the words “group” and “pentagon” in reference to different impressions. Nonetheless, the same report for the same stimulation allows one to infer that each subject has seen something similar to the appearance that a pentagon outlined on a piece of paper would bring about. The experimenter need not know what the impres­sions of each subject are like. She needs only to observe that the subjects give the same verbal reactive, whence it can be stated that each subject in the situ­ation A, which differs from the situation B as the set of dots differs from the drawing, has the same experience he would undergo if faced with B. Converse­ly, there are cases in which every subject in the situation A that is partially similar to B has the same experience, which is nonetheless different from that which he would undergo in B. Thus, the phenomenal data are not subjective impressions, rather the similarity or difference given the relations among well- defined stimulation conditions. Similarity and difference are not impressions that may vary across the subjects, since it is sufficient that what subjects call “similar” occurs with the same stimulation conditions. It is the constant use of words any time the subjects experience a similarity or difference in what ap­pears that really matters.

Michotte (1962) concedes that behaviourism and phenomenology might share this method, yet there is another procedure toward a proper experimen­tal phenomenology. Stimuli can be designed as a whole system of stimulations that likely bring about the phenomenal patterns that underlie the perceptual scenes of everyday life. In this sense, a system of stimulation is designed as a trigger of a pattern of possible perceptions. If the reference to a phenom­enal pattern is constant, the subjects’ perceptual reports can be collected and classified on the grounds of the characteristics of the descriptions they give about it. If the descriptions share some characteristics, then it is possible to extract from them the features of that kind of perception both in the experi­mental setting and in the corresponding naive circumstances of everyday life. The descriptions are no longer simply indicators of something that occurs sys­tematically for determinate stimulations, but also potential hypotheses on the features that appearances have across the subjects. Once the hypotheses are formulated, they are tested by the method of “concomitant variation.” If some descriptions are obtained given the values of a determinate system of stimula­tion, from which the set of features X, Y, Z is abstracted, and if the descriptions change when those values are varied and a set of partially or totally different features is abstracted, then the former set of features specifies a structure of the appearances. The change of descriptions is the evidence that a structure is altered or has disappeared because of the occurrence of different charac­teristics that are brought about in the pattern by the concomitant variation of the stimulation. In such cases, the former structure has to be replaced by a partially or wholly different structure. Accordingly, testing the descriptions against systems of stimulations allow one to distinguish the phenomenal fea­tures of perception. Some features recur, others need a specifiable variation in the systems of stimulations to occur. If the hypotheses are confirmed, this procedure permits one to formulate new concepts and laws that apply to the shared phenomenal world of subjects.

Michotte holds that the phenomenological nature of the structures that are discovered by the method of the concomitant variation is attested by the fact that the phenomenal patterns are only schemes of possible perceptions. This schematic nature permits one to eliminate the influence of familiarity, hab­its, past experience, memory, which likely contribute to perception to various extents. Likewise, it can be excluded that the features of appearances derive from the stimuli that trigger the patterns, for it is possible to design conflicting systems of stimulation. Indeed, appearances can be obtained that turn out to be paradoxical in the light of what was expected to appear on the grounds of the knowledge of the stimuli. This method allows one to decide whether “X appears such and such because subjects know that X” or “subjects know that X because X appears such and such.” If the latter case is proved, the features and structures of perception explain the appearances brought about by the systems of stimulation and at the same time represent the rules of the lawful relation between the naive subjects and the world.

Michotte (1955) emphasizes this heuristic role of the conflicting systems of stimulation, which he also calls “discordant systems of stimulation.” He lists a series of conditions ordered in a continuum between the opposite ends of inconsistent systems of stimulation, which cannot but yield confused or cha­otic appearances, and incompatible sources of stimulation for the same object, which yield a contradictory appearance thereof. Some objects performing ir­regular motions, or one object undergoing simultaneously a change of form and a rotation, exemplifies the first end. A hemisphere with a flat rear face, which is seen as a complete round object while the rear face is simultaneously touched as flat, exemplifies the second end. In the first kind of case, subjects usually report that they do not know what they see, not for lack of concepts or words but because the very perception is without order and organization. In the second kind of case, subjects may ascertain the perceptual contradic­tion that nevertheless does not disturb the mutually inconsistent beliefs in the visual roundedness and the tactual flatness. Various kinds of discordant stimulations can be designed between these ends, whose conflict brings about the appearance of competing perceptual properties or of a unitary object that is a compromise between them. Michotte gives many examples of such a compromise, ranging from the purely perceptual trade-off to the ones in which there is also a contribution by psychic functions.

If subjects are presented with a parallelepiped made of wire, its perspective pictorial representation, and various solid models thereof which are of fixed sizes and placed at different distances, and asked to judge the apparent depth equality, their gauges depend on the magnitude of the perceptual compromise in the pictorial representation between the conflicting appearances of the lines either as the edges of a real thing-like volume or as signs on a flat plane. A balanced compromise is reached when the representation is perceived only as a seeming real volume, namely as a “mere appearance” of a solid that the perceivers do not believe to be real. Other examples are the discordant systems of stimulations whose corresponding appearances develop toward stable phe­nomena, notwithstanding their features are inconsistent with what the sub­jects know in general or in particular about the experimental conditions. If two red and yellow crescents are drawn on a disc with an orange oval in the middle, when the disc is set in motion a red circle appears sliding over a yellow circle that is transparent in the area of the orange oval (as Michotte remarks, this phenomenon had been earlier observed by Benussi). If one chooses colors that are not complementary, like blue and red for the crescents and yellow for the oval, the discordance of the system of stimulation is increased, and Michotte (1955: 78) emphasizes that the appearances that are thus brought about chal­lenge the known laws of the physics and the physiology of colors. First a red cir­cle appears that is covered by a bicolored blue-yellow circle, then a blue circle appears that slides over a red circle so that when the blue crosses over the red circle the covered part of the latter becomes visible through transparency even if it now appears yellow. Finally, a hollow cylinder appears with a blue outer surface, a red inner surface and a yellow bottom surface, which simultaneously rotates and turns. Then phenomenal transparency, three-dimensionality and movements attain a perceptual compromise for the discordant properties of this system of stimuli. For instance, turning and rotation allow the compet­ing phenomenal properties to be distributed on the distinct sides of the solid, making them appear one after the other. The Rosenbach effect and the modi­fications of the original appearance of the Ames room exemplify the extent to which psychic functions can contribute to the perceptual compromise. In the first case, the discordant conditions are such that an opaque occluder, under which a moving object is amodally completed, appears transparent (Glynn, 1954). In the second, asking subjects to hit light spots in the Ames room by launching a ball or to observe another subject in order to follow the edges of the room with a long stick causes the real form of the room to appear (Kilpat­rick, 1954).

In addition to the schematic nature of the pattern, the discordant properties of the system of stimuli allow one to discover the characteristic features and structures of perception. The conflicting appearances that arise are traded off against one another in a phenomenal compromise depending on the nature of perception itself (Michotte, 1955: 83). The descriptions reported in such condi­tions are about the perceptual compromise, while their content is inconsistent with the knowledge of the physical properties of the stimulation or do not fit what could be expected to appear on the grounds of physiological laws. Besides, the method of concomitant variations through the construction of discordant systems of stimulation precludes that descriptions are induced by higher-level psychic processing of sensory data. Michotte (1962) remarks that if one be­lieves that perceptual responses are determined by judgements grounded on a knowledge base, it is difficult to explain how and why little differences in the systems of stimulation of a few millimetres or centiseconds have an influ­ence on the correct inference or the selection of the relevant past experience. Some examples at one end of the continuum do attest that learning at least may exert an influence on perceptual responses. Yet, the fact that these cases are at one extreme allows one to conclude that this influence can be disen­tangled from perception and that, whenever it takes place, it is grounded on a perceptual basis. Michotte (1955: 82) remarks that in the modified perception of the Ames room, the perceptual compromise is the appearance of the room as it really is rather than as an orthogonal room that should have appeared in conformity to its greater stability. The original appearance of the Ames room is thus modified in the inverse direction with regard to how rooms are in ev­eryday experience. He also claims that even the traditional account in terms of illusions should be rejected. The construct of illusion is usually applied to solve a conflict when what is known with a high degree of certainty is at odds with what is perceptually present (1955: 85b). In such a case, however, the problem regards the reliability of distinct sources of information. If they have different natures, like conceptual knowledge and perception, the choice between them results from a long and progressive process of acquaintance and tacit learning of the circumstances of experience. For example, in circumstances like attend­ing conjuring tricks or being experimental subjects in a laboratory, a reflection or a conviction is sufficient to make a conflicting phenomenon disappear and to put the perceptual source of information into question. Therefore, a defined class of appearances can be characterized by disbelief. When the conflict aris­es from within the appearances themselves, knowing what is physically the case does not prevent that perception from occurring. When seeing a movie or observing the appearances triggered by conflicting stimulations, appearances are still forced upon subjects even if they know what the cinematographic or experimental devices are made of. Furthermore, in most cases subjects cannot be acquainted with physical situations that could be an alternative source of information. In everyday life, it is the perceptual experience itself that gives subjects the elements to consider whether and to what extent certain appear­ances, like color or form, are not thoroughly reliable. Otherwise, the problem will not even arise. At the most appearances elicit such reactions as “I can­not believe it is an illusion.” Therefore, Michotte concludes that even though the belief in appearances is not absolute, it does not mean that perception is subject to disbelief. If from the experimental point of view “perception” is un­derstood to denote also the system of stimuli, even if it is observable only for the experimenter, then the method of the concomitant variation allows one to investigate the phenomenal structures of the quantitative relationships that enable subjects to successfully adapt their behaviour to the ordinary circum­stances of the environmental world (1955: 90-91 n. 3).

Source: Calì Carmelo (2017), Phenomenology of Perception: Theories and Experimental Evidence, Brill.