Chapter 1

Perceptual Problems

Michael Wertheimer

0. Introduction
1. The Distal Event
2. Transmission Processes
3. The Proximal Stimulus
4. Neural Encoding: Sensation
5. Perception
6. Cognition
7. The Report
8. An Evaluation
BACK to Contents

Perception plays a role in the report of any unidentified flying object. Someone perceives -- i.e., sees, hears, feels, etc. -- something, and it is his conclusion concerning what it was that he perceived that results in an UFO report.

This chapter is devoted to some well known principles of perception, with special reference to how they apply to the processes that result in UFO reports. Basic accounts of perception and further details on the matters considered here can be found in such standard texts as Bartley (1958), von Fieandt (1966), Dember (1960), Beardslee and Wertheimer (1958), Gibson (1950), Forgus (1966), and Boring (1942). Lively, brief introductions to general problems of perception have been written by Hochberg (1964) and Leibowitz (1965).

Our discussion in this chapter is organized around the physical, physiological, psychological, and social sequence of events that eventuates in UFO reports. This sequence of events usually begins with some actual distal physical event (an energy change or source some distance away from the observer), resulting in the transmission of energy to the observer's sense organs. The energy that arrives at the observer's sense organ, the proximal stimulus, is encoded into neural events, producing sensations which are combined into percepts and finally into cognition. By this process, the observer becomes aware that there are some particular phenomena having particular characteristics taking place in some location at some particular distance and direction from the observer.


A report eventuates from this sequence only if the observer's cognition is such as to produce in him the conviction that what he has experienced should indeed be reported.

Since most of the observations reported in connection with UFO phenomena are visual, we shall consider each of the foregoing steps in terms, primarily, of the processes of visual perception.


1. The Distal Event

An actual, physical event usually precedes the report of an UFO. Chapter 2 of Section VI discusses in detail some of the distal events that could give rise to UFO reports. In section 4 below, reports that arise despite the absence of any stimulus exterior to the observer are considered. For the purpose of the present discussion, however, we need emphasize only the fact that the distal events that give rise to UFO reports always involve the transmission of some form of energy. As we have pointed out earlier, that energy is usually in the visible spectrum.


2. Transmission Processes

The energy is transmitted from the distal source and arrives at a sense organ, where it produces a proximal stimulus in the form of an energy change to which the sense organ is attuned. But the energy arriving at the sense organ is not an exact copy of the energy that left the distal source. It is attenuated and distorted, and often is an incomplete version of the original (Brunswik, 1956). If, like most energy sources, the transmitted or reflected light obeys the inverse square law, the energy arriving at the sense organ is far weaker than at the source. Further, the characteristics of the medium through which the energy is transmitted distort and disrupt the energy. For example, mist, ground fog, smoke, rain, snow, fog, dust, temperature inversions and discontinuities, and other atmospheric phenomena


can cause gross attenuation. They can also distort the energy by selectively filtering out or modifying certain components.

Turbulence in the air and peculiar temperature inhomogeneities can produce major distortions in the transmitted energy before it becomes a proximal stimulus (Minnaert, 1954). Intensity, "shape," color, direction, and other attributes can all be grossly altered. Atmospheric turbulence phenomena can, for example, cause distant mountains seen across a heated desert to shimmer and to change their shape eerily in an amoeba-like fashion. Other well known kinds of mirages, discussed in detail in Section VI, Chapter 4, are superior and inferior mirages resulting from sharp temperature inhomogeneities in the air.

Other modifications of transmitted energy occur when the energy passes through glass, plastic, the exhaust of a jet, over a heated surface, etc. before reaching the observer.

Frequently the transmitted energy is so modified by the characteristics of the medium through which it has been transmitted that the proximal stimulus is far from an exact replica of the energy that left the distal energy source.


3. The Proximal Stimulus

Aside from the foregoing phenomena of attenuation and distortion, the proximal stimulus itself may be quite impoverished. It may be difficult to tell, from the proximal stimulus alone, what the characteristics of the distal object actually are (Brunswik, 1956). Ambiguity occurs, for example, in size and distance estimation. A nearby, small object will cast the same image on the retina as will a larger, more distant one. UFOs are frequently observed under conditions providing no frame of reference from which distance and size may be inferred. Without such a clear frame of reference, judgment of size and distance is extremely difficult or impossible. Thus, an


unknown, vaguely defined object in the undifferentiated sky can appear to be of any size or at any distance, depending on the inferences made by the observer. If he assumes the object is the size of an automobile, he will infer its distance in terms of that size. But if he assumes that it is the size of a teacup, he will infer that it is much closer to him. Even if the object is within a few yards of the observer, distance and size judgments can be grossly inaccurate for lack of a frame of reference, because the retinal image alone does not typically (and especially in the case of UFOs) supply enough information to the observer to permit determining whether it has been cast by a huge, very distant object, by a medium-sized one at a moderate distance, or a small one close by.

A typical example of this ambiguity is found in the reports of witnesses to the re-entry of fragments of the Soviet satellite, Zond-4, on 3 March 1968 at about 9:45 p.m. EST. Three witnesses reported seeing a single object traveling at "tremendous speed" at an altitude of "not more than 2,000 to 5,000 feet." The witness quoted is the chief executive of a large U. S. city. Another group of witnesses to the same event reported that "it was at about tree-top level and was seen very) very clearly and was just a few yards away." They estimated that it was 175-200 ft. long. A private pilot saw more than one object moving at "very high speed" and estimated the altitude at 30,000 ft. An airline pilot and his crew reported the objects as "heading in a NNE direction at high rate of speed & above 60,000 feet altitude." The observers were actually looking at several pieces of satellite debris entering the atmosphere at an altitude of about 100 mi. and at a speed of about 18,000 mph (Sullivan, 1968).

Estimates of speed are just as ambiguous as estimates of size and distance, as the foregoing demonstrates. The retinal image, and the successive changes in it, can be the same for a small, near object moving slowly as for a large, distant object moving rapidly. Apparent


speed depends upon relative displacement within a framework, rather than upon absolute displacement across the retina (Brown, 1931).

The characteristics of motion are also inherently ambiguous, especially if the moving object is unfamiliar. A proximal stimulus that is actually rising could be produced by an object rising and receding from the observer or one rising and approaching him. Its actual path could be perfectly horizontal, if it is above eye level and is approaching the observer. It could even be an object whose actual path is descending if the path is one that will eventually pass over the observer's head. Still other distal stimulus movements could produce the same proximal stimulus.

Changes in the size of the proximal stimulus are also ambiguous. They could be due to approach or recession of the object, or to changes in its size while remaining stationary. An object whose proximal stimulus is gradually growing can actually be receding from the observer, if the retinal image is growing faster than it would shrink because of recession alone.

Nor does the shape of the proximal stimulus unequivocally represent the shape of the distal object. Many different distal objects could cast the same shaped retinal image simply because at a given orientation they present the same cross-section. Conversely, except in the case of a sphere, a given distal object can produce many different shapes of proximal stimulation. Consider a flat disk. In different orientations to the observer, it could look like a vertical line, a horizontal line, a slanted line, a cigar-shaped object in various positions, a circle, or many forms of ellipses.


4. Neural Encoding: Sensation

It is clear from the preceding that what is physically available to the observer, the proximal stimulus, is by no means an exact, information-filled, unambiguous replica of the originating event, the


distal energy source. The distortions we have considered so far are purely physical; precise instruments would register them in a way that is comparable to the way in which human sense organs register them. With our discussion of sensation, we enter the skin of the observer, and must consider physiological and psychological events that occur inside him.

When the proximal stimulus reaches the cells of a receptor that is sensitive to the energy contained in the stimulus, the cells transform the light, sound, heat, etc. into impulses carried along nerve fibers. The impulses travel from cell to cell into the center of the brain, the thalamus, and thence to the outer layer of the brain, the cerebral cortex. A sensation depends upon the messages arriving at higher sensory center in the brain in combination with other events simultaneously occurring in these centers.

What actually goes on in the sensory areas of the cortex depends on many things. Thus whether a dim light is actually seen is a function of how dark-adapted or light-adapted the eye is. If one comes into a dark movie theater from a bright, sunlit street, at first he can barely, if at all, make out the seats and the other people, but after some time in the dark, things that were previously invisible to him become visible. Conversely, if the eye has been in the dark for some time a moderately intense light will appear so bright as to be blinding, and it may be impossible to tell what the light source is, even though it would be readily recognizable to the light-adapted eye. Clearly the sensation produced by a particular proximal visual stimulus varies greatly with the state of adaptation of the eye.

Second, the observer's state of alertness can affect how and even whether he will sense a given stimulus. If he is drowsy, fatigued, tired, intoxicated, dizzy, ill, or drugged, he will be a less sensitive, less accurate, more error-prone instrument for detecting stimuli. Spontaneous discharges in the sensory centers of the brain may be


interpreted by him as distal events, even though there may be no corresponding proximal stimulus. In addition to these physical conditions, states of extreme tension or anxiety can also produce not only reduced alertness but an enhanced tendency to misinterpret or distort sensations.

Third, concomitant sensory events can modify sensations. A loud noise, absorption in a book, concentration on a TV show, etc. can make one less likely to notice something else. In fact, one stimulus may actually inhibit the neural events produced by another. In a now-classic experiment, investigators recorded the bursts of neural activity in the auditory nerve of a cat whose ear was stimulated by clicks; when a caged rat was placed before the cat, impulses in the auditory nerve stopped, even though the clicks still continued at the same rate and intensity (Hernandez-Peon, 1958).

Fourth, various sensory anomalies can modify sensation. A sizable proportion of the population is color blind to some degree; many persons are nearsighted, or farsighted, resulting in fuzzy contours, while astigmatism results in various shape aberrations. Phen there are the phosphenes, or entoptic phenomena: visual sensations produced by pressure on the eyeball, or from such other conditions as spontaneous neural discharges within the eye. One can obtain brilliant, brightly-hued floating shapes intentionally by closing one's eyes and applying moderate continuous pressure to the eyelids with one's fingers - fascinating swirling abstract designs will result, with ever-changing brilliant colors.

Fifth, there are several kinds of afterimages, or images that persist after the stimulus originally producing them has ceased. In a positive afterimage the sensations are the same as those in the inducing stimulus, while in a negative afterimage they are reversed. If, in darkness, a bright light is flashed in the eye the afterimage of the light can be seen floating eerily about, moving as the observer's


eyes move, for as long as a minute or more. The image can hover, dart here and there, and change apparent size, depending upon where one happens to cast it. The color typically changes as the image gradually fades. The color can range through the whole spectrum, and typically alternates between the color of the original light and its complement. Negative afterimages are more common than positive ones, and are produced by staring for a time at a particular place in the visual field. The characteristics of the negative afterimage are opposite to those of the inducing stimulus. Thus where the original stimulus was white, the afterimage is black; where it was black in the stimulus the image is white; where the stimulus was red the image is green; where the stimulus was blue the image is orange-yellow; and so on. Negative afterimages fluctuate like positive ones, fading in and out. The longer the inducing stimulus was stared at and the greater the contrast in the inducing stimulus, the longer the afterimage persists. The apparent size of afterimages, both positive and negative, depends upon the distance to the surface upon which they are projected: the farther away the surface, the larger the image appears to be.


5. Perception

Perception is the process of identifying the distal object. The observer interprets the neural inputs as due to some object, assigning it particular characteristics, such as distance, direction, shape, color, etc. The amount of interpretation that the observer must employ to arrive at the final percept depends in part upon the clarity, the lack of ambiguity of the input. Thus the letters on this printed page are reasonably clear and unambiguous; there is an ample frame of reference, and the distal stimulus is clearly structured: the observer can obtain a fairly accurate percept of what the distal stimuli actually are. But if the perceptual framework is impoverished, as is true of most conditions under which UFOs are reported, then the perceiver must engage in much more interpretation before he arrives at a percept.


Typically, perception results in a clear, categorical conclusion about characteristics of perceived objects, even if the input is logically, geometrically or optically insufficient to specify these characteristics unambiguously. For objects in the sky, again, especially unfamiliar objects, shape, size, distance, direction, speed are all basically indeterminate in the proximal stimulus, and yet the processes of perception work in such a way as to give each a particular value in any given case.

Apparent shape depends upon the orientation of the object to the observer. Size, distance and speed depend upon each other in a complex way: an observer's automatic assumptions concerning one of them determine to a large extent how he will perceive the others. Apparent direction of motion depends upon a reference frame; thus clouds, for example, will typically appear to be moving at right angles to a reference line such as the roof line of a house or the part of a window frame one concentrates on while looking through the window at the moving clouds.

Apparent motion can be induced in an actually stationary object in a number of ways. The moon may appear to be moving while the clouds partly covering it seem to stay stationary. The landscape may seem to move in a direction opposite to that to which the eye was previously exposed, as when one sits in a train which has just stopped, or looks at the hillside next to a waterfall after staring at the waterfall a while. Normally a single object in a completely unstructured field will soon appear to move, even though it is actually stationary. This phenomenon, autokinesis, is frequently studied by experimental psychologists who ask subjects to report on the appearance of a pinpoint of light in a completely dark room. A light going out typically seems to shrink as it does so. A light that goes on as another is going off can, under proper time and space conditions, be made to look as though the light that went off had moved to the place where the light went on.


The angular elevation, or apparent location above the horizon, of objects is generally not estimated very accurately at all. The difference from 0° or from 90° of angles near the horizon or near the zenith tends to be substantially overestimated. Anything that is more than 45° or even 30° above the horizon is often reported as overhead.

Colors are sometimes perceived by interpretation only. The dark-adapted eye is insensitive to color, yet the grass still is perceived as green, a banana as yellow. There are also phenomena of color contrast or color induction: a small piece of gray paper on a strong green background takes on a reddish tinge; on a strong blue background it will take on a yellowish tinge. The same piece of gray paper looks appreciably brighter on a black background than on a white one.

In general, for just about all perceivable characteristics, perception typically works in such a way that the percept, as the perceiver is aware of it, is considerably clearer, less ambiguous, and less vague than the actual physical proximal stimulus warrants.


6. Cognition

One's judgment, conviction or belief about the actual identity and meaning of something, that is, one's cognition of it, are very much affected by mental set, expectation and suggestion. Every observer is ready to perceive reality in a certain way. The observer's sets and expectations arise from his experiences, opinions, and beliefs, including those derived from suggestion. The observer who looks for faces in cloud patterns or leaf patterns can find them easily. Setting oneself to see the letter "e" on this page makes the e's more salient, more noticeable. You probably were unaware just now of the pressure of the shoe on your left foot until it was mentioned in this sentence. What one notices, pays attention to, responds to, and how one interprets it, what it means to one, are deeply affected by one's attitudes, past experiences, opinions, and beliefs (Bruner, 1947; Dember, 1960; etc.)


The influence on cognition of all these internal factors is especially strong in impoverished stimulus situations such as those under which UFO reports typically are generated. The observer's personality, his rigidity, absolutism, skill in scientific thinking, interest and belief in UFOs, readiness and ability to consider alternative interpretations of what is perceived, etc. substantially affect the observer's conclusions, typically without his being aware of this influence.


7. The Report

Whether the observer makes a report, and, if so, to whom and in what form, varies with the individual and with the situation. A frightened observer, or one who is oriented toward authority, is more likely to make a report than one who is unconcerned, or who does not know to whom to make a formal report. Once the observer has decided to make a report, the way in which he is questioned can substantially affect its content. The amount of detail and even the details themselves, can be much affected by the manner and form of questioning by the recipient of the report. Open questions (e. g., "Tell me what you saw.") result in less distorted answers then do closed questions'(e. g., "Did you see it for longer or shorter than ten seconds," or, "You don't mean to tell me that it actually hovered, do you?"); interviewer bias can greatly influence the respondent's behavior (Rosenthal, 1966). Testimony is known to be quite unreliable especially under the pressure of leading, direct questions, a hypercritical or incredulous interrogator, or one who insists upon details about which the witness' memory is fuzzy. Memory of the percept like cognition, is subject to the distorting effects of motivation, personality, set, suggestion, etc.


8. An Evaluation

UFO reports are the product of a long chain of events, from distal stimulus through to the final reporting; at every link in this chain


there are sources of distortion. Details of specific reports, are, by the very nature of the processes of human sensation, perception, cognition and reporting, likely to be untrustworthy. Thus any report, even those of observers generally regarded as credible, must be viewed cautiously. No report is an entirely objective, unbiased, and complete account of an objective distal event. Every UFO report contains the human element; to an unknown but substantial extent it is subject to the distorting effects of energy transmission through an imperfect medium, of the lack of perfect correlation between distal object and proximal stimulus, and of the ambiguities, interpretations, and subjectivity of sensation, perception and cognition.




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