The Structure of Phenomenal Permanence

The work of Michotte ([1950] 1991) on phenomenal permanence shows that perceptual time consists of self-sufficient structures. Perception does convey information on properties, events and states of the perceivable world but as a function of such structures. Phenomenal permanence corresponds to per­ceiving a thing or an event as something that continues to exist or persists before and after the occurrence of the corresponding stimulation. The experi­ence one has when observing conjuring tricks attests that this perception is not the result of beliefs in the nature of physical objects derived from past ex­perience or the scientific knowledge that has become part of common-sense. Michotte remarks that one cannot but perceive that something, amazingly, is beginning or ceasing to exist as soon as it appears or disappears, even though one knows that this does not fit any current knowledge of the environmen­tal world. This experience shows that perception of permanence rests upon a phenomenological structure. Although it is at odds with common-sense be­liefs and knowledge, the conjuring trick succeeds because the becoming vis­ible of a thing coincides with the coming into existence of it, which attests a violation of the distinction between two fundamental aspects of things: the perception of the time in which they begin to either exist or appear. Michotte emphasizes that this distinction does not depend on the stimulation that actu­ally impinges on the subject’s nervous system. In a dark room that is suddenly lit, the furniture does not appear to come into existence as soon as the light is reflected off of it, rather it simply becomes visible as something that was already there. Therefore there has to be a phenomenological structure of per­ceptual permanence. There is no logical difference between something being concealed by the conjurer and its being kept from sight because it is contained in a drawer or made invisible by darkness. Nevertheless what is perceptually the case differs. In the first case, things seem to be created or annihilated as they appear or disappear. In the other two cases, things persist as they happen to appear and disappear.

In order to study phenomenal permanence, Michotte employs the para­digms of the screen effect (Knops, 1947) and of the gamma movement (Ken- kel, 1913). In the first paradigm two figures A and B with different colors are projected on a screen so that they appear contiguous with a piece of border in common.

By smoothly introducing an occluder, B is gradually made to disappear until only A is visible. Then by smoothly removing the occluder, B is gradually made to appear until it is again wholly visible. If the speed of the introduction and the removal of the occluder amounts to a few cm/sec., subjects do not see B growing shorter and longer in opposite directions according to the projection. Instead they see in B one and the same object with indeterminate length but constant form that slides behind A, either coming out of it or hiding behind it. The perception of permanence takes place, because B is present as a whole even across the phases in which some parts of it are either no longer or not yet visible. If the speed is about 1 m/sec., subjects see B suddenly appear alongside A as if it were created out of nothing. Michotte holds that at a moderate speed the same stimulation, that is, the lengthening and shortening of the area of B due to the occluder motion in the projector, brings about a phenomenal scis­sion: the sliding of B that appears to unfold in time, the constancy of B that appears to persist in time. The gamma movement allows one to observe the strength of the phenomenal scission. In general, the gamma movement is the movement of the parts of a figure presented through the tachistoscope with exposure of about 100 msec. If the figure is a disc, at the beginning of the ex­posure it appears to expand from the center until the periphery is reached, at the end it appears to contract in the inverse direction. If B is presented in this condition, when it becomes suddenly visible it exhibits the gamma movement. Its surface appears to expand so that B appears to come into existence as soon as it begins to appear. B looks as if it were created at that instant.

Michotte argues that as visual boundaries are an essential feature of the spatial structure of visual things, so temporal boundaries are essential features of the temporal structure of permanence. Figures A and B have a common con­tour that nonetheless appears as the unilateral boundary of A. This explains why B is perceived to slide behind A. The parts of B that become gradually visible or invisible as it slides do not appear as new parts, that is, as not exist­ing before or ceasing to exist after, but as the parts of B that have been or will be occluded. As the common contour takes the value of a perceptual spatial boundary solely in one direction, so the projective lengthening or shortening of B becomes a perceptual temporal boundary solely in one direction. As it takes the value of the unilateral boundary of the sliding, this is perceived as a process unfolding in time. Therefore B is not perceived with a backward or forward temporal boundary. As B continues to exist in the space occluded by A, so it continues to exist in time while sliding behind A. Since B does not have a backward boundary, it is perceived to be already present in an indeterminate past so that as B slides out from behind A, appearances make its earlier exist­ing parts progressively visible. Since B does not have a forward boundary, it is perceived to be still present in an indeterminate near future so that as B slides behind A, appearances make its existing parts progressively invisible.

The structure of the perception of permanence is not established with a higher speed of introduction and removal of the occluder. With a fast length­ening or shortening of B with gamma movement, the boundary inverts the di­rection and becomes the unilateral boundary of B by which it is delimited in time in the same way as A is delimited in space. Therefore, the instant in which B becomes visible coincides with the instant in which it is seen to begin to ex­ist. B appears to be created as it appears or, conversely, to be annihilated as it disappears, just as in the conjuring trick.

This phenomenological structure also accounts for the perceptual perma­nence of the furniture in a dark room that is suddenly lit. Michotte reduces this case to the following system of stimulation. Subjects look at a dark region of the visual field, for instance a black cardboard. After a while, a grey square with a face drawn on is projected on it. Subjects report seeing either a square with a face appearing out of nowhere on the dark field, where earlier there was noth­ing, or a square with a face that was already present in the field that becomes visible through the light that has fallen on it. Next, the system of stimulation is varied. Subjects look at a dark region of the field in which a light grey square is already present. While they fixate the center of the square, this is suddenly replaced by an identical square with a face drawn on it. All subjects report seeing a face that comes out of nothing, that is to say that is created as soon as it appears. Some subjects also report noticing a gamma movement of the second square. In the first case, there is a phenomenal scission between the grey square that appears as illumination and the drawn face that appears as a stable independent object. Like for the sliding in the screen effect, the square is seen to unfold in time so that the face appears to endure, that is, to prolong its existence in time. In the second case, there are competing features that bring about a different phenomenal scission. The grey square is identical in the first and second phases, hence it cannot be seen to develop in time. Rather it appears stable. The character of a sudden developing appearance is ascribed to the face that is perceived to unfold in time. It is also seen to undergo the gamma movement effect. In this case, illumination is seen to be pre-existent, while the face looks like it is being created in the same instant in which it be­comes visible.

The temporal boundaries that characterize these phenomenal structures are also found in ordinary cases. The first case corresponds to what we usually see in a suddenly lit room, while the second corresponds to what we see in a conjuring trick. Illumination has the same phenomenal value of the sliding in the tunnel effect or the face on the identical grey square; hence, it acquires the unilateral temporal boundary and appears to unfold in time. The furniture is segregated apart from this boundary, like the figure B. Since it has no backward boundary, it is seen as already existing in an indeterminate past, so that the time in which it becomes visible is not coincident with the time in which it has come into existence.

A meaningful implication of Michotte’s investigation is that phenomenal time presents itself in two distinct guises. On the one hand, it is an ordering of things and events that fall into perception. Every perceptual thing and event hold a stable position in relation to others in time. On the other hand, it ap­pears as an inherent feature of perceptual things and events. The unilateral character of temporal boundaries implies that things and events are delim­ited in time in the same sense in which they are delimited in space. Temporal boundaries are features of things and events as much as spatial boundaries are features of surfaces and things that are regarded as independent unities in a surrounding space.

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