Terence Hines - Pseudoscience and the Paranormal

Color and size constancy are just two examples of many perceptual constancies. Others include position constancy, shape constancy, and brightness constancy . Details can be found in most introductory psychology texts and any textbook on perception. The important point about these constancies is that they demonstrate that even in such straightforward tasks as judging color or shape or size, knowledge plays an extremely important role in influencing the way in which an object is perceived. The brain takes into account what is known about the object and constructs a perception based both on the actual sensory input and on knowledge.

Other perceptual processes contribute to the constructive nature of perception. Look at the object in figure 9, then close the book and make a copy of it from memory. Chances are very high that you did not include in your copy the small gap at one corner. If you had been asked to describe the figure to someone, you would almost certainly have left out that small gap. This is an example of perceptual closure . Along with several related processes, it tends to “clean up” a perception and make it into more of a unified object, even if the stimulus was not such an object in the first place.

An impressive example of constructive perception that is not well understood physiologically is that of illusory contours (Coren 1972), seen in figure 10. The triangular shape you see isn’t really there; the brain constructs it.

The constructive nature of perception accounts for a famous astronomical illusion—the canals of Mars. These were first reported in 1877 by the Italian astronomer Giovanni Schiaparelli. They were popularized in the early twentieth century by the American astronomer Percival Lowell. Figure 11 shows a map of the canals from Lowell’s 1908 book Mars as the Abode of Life . In this book Lowell argued that the canals were constructed by an advanced Martian civilization. It turns out, however, that the canals of Mars don’t exist. Sagan and Fox (1975) have compared the photos taken by Mariner 9, which photographed the entire Martian surface, with maps of the canals. When the actual Martian surface is examined, there are no canals and or physical features that could account for what Schiaparelli and Lowell reported. So where did the canals come from? Sagan and Fox state that “the vast majority of the canals appear to be largely self-generated by the visual observers of the canal school, and stand as monuments to the imprecision of the human eye-brain-hand system under difficult observing conditions” (p. 609).

A number of well-known visual illusions play a role in what witnesses report in UFO sightings, especially those that take place at night. One is the autokinetic effect . This effect refers to the fact that, if one views a small source of light in a dark room, the light will appear to move, even if both it and the observer’s head are stationary. One theory is that the effect is due to tiny movements of the eyeball that are not under the conscious control of the observer. These tiny eye movements cause the image of the light to move across the retina. The brain incorrectly attributes this movement to the light source, since the head is steady and the brain itself receives no information from the eye regarding the tiny eye movements. The effect is eliminated if a clear frame of reference is provided so the brain can compare the position of the light source with that of a larger, clearly stationary object (Haber and Hershenson 1973). Otani and Dixon (1976) showed that social influence can affect the degree of the autokinetic effect—that is, one person saying he sees the light moving in a particular direction can induce others to make similar reports.

Another illusion is that of apparent motion . Consider two positions in a dark room, A and B. A small light is turned on at A, then turned off. Moments later, a second light is turned on at B. What does the observer perceive? The obvious answer would be that the perception is of one light going on and going off, followed by a second light in a different position going on and then off. But this is not what the observer sees at all. What is perceived is a single light appearing at point A, moving to point B, and then going off. The brain creates a perception of movement where none exists. It also creates a perception of light where none exists—between positions A and B.

These constructive phenomena are extremely important for our survival in the real world. The constancies and other mechanisms described evolved because they help organisms interact with the world. However, when the sensory input is minimal and only our knowledge and beliefs remain, our resultant perceptions can be very, very misleading. In these situations, we can perceive complex objects that are not there at all, and be absolutely convinced that they were there. People who report seeing impressive flying saucers are not lying. They really perceive them, even though they weren’t there: The objects were a construction of their brains and seem just as real as if they actually had been there. Before moving on to the numerous UFO sightings that prove this point, it is important to discuss briefly the fallibility of human memory.

You don’t need expertise in experimental psychology to know that human memory is fallible. Anyone who has ever taken an exam or tried unsuccessfully to remember someone’s name or telephone number knows that human memory doesn’t always work perfectly. The most important insight about the fallibility of human memory to come from experimental psychology over the past thirty years is that memory is fallible in a very special way. It can be changed after the fact by new information, and the resultant memory may be very different from what actually took place—yet the person will swear that his or her memory is accurate. In some sense, it is. The witness is not lying in the usual sense of that word: The reported memory is really a memory, but due to the nature of memory, the reported memory differs greatly from what actually happened.

The best examples of this process come from the early work of Elizabeth Loftus (1979), whose more recent work is described in chapter 5. In one of her experiments (Loftus and Palmer 1974), Loftus showed students in her introductory psychology classes a film of a car accident. Afterward, the students were given a questionnaire to fill out about the accident they had seen. There were two versions of the questionnaire, identical except for one word. One version of the questionnaire had as one of the ten questions: “About how fast were the cars going when they smashed into each other?” The other version of the questionnaire was identical except that “hit” was substituted for “smashed into.” This slight change had two effects. First, students who got the “smashed into” question gave higher speed estimates than those who got the “hit” question. More important for the issue at hand, when asked one week later whether or not they had seen any broken glass in the film, students who had answered the “smashed into” question were more than twice as likely to report seeing broken glass as those who received the “hit” question (16 percent versus 7 percent). There was no broken glass in the film. Thus, a leading question given after the fact can alter a memory, not only for the actual subject of the question—speed, in the present case—but also for related material.

Loftus demonstrated how powerful this effect can be in a later experiment (Loftus, Miller, and Burns 1975). She again showed subjects a film of a car accident. After the film, subjects were given a questionnaire about the film. One of the questions was “How fast was the red car going when it ran the stop sign and hit the green car?” In fact, there was no stop sign at the intersection in the film where the accident occurred. A week later subjects were shown two photographs. One showed the intersection as it had actually appeared in the film, without a stop sign. The other showed the same intersection, but with a stop sign. Subjects were asked which picture was from the film. They overwhelmingly picked the picture with the stop sign, even though there was no stop sign in the film. The question that presupposed the existence of a stop sign had implanted a stop sign in the subjects’ memories, even though none had been there. As before, the subjects were not lying—they really remembered seeing a stop sign, even though it had never been there. Loftus’s work has important implications for eyewitness testimony in court, and Loftus (1979) has addressed this issue. Her findings also have extremely important implications for UFO reports, as will be seen in the next section.