“It is a well-known phenomenon that we do not notice anything in our surroundings while being absorbed in the inspection of something: focusing our attention on a certain object may happen to such an extent that we cannot perceive other objects placed in the peripheral parts of our visual field, although the light rays they emit arrive completely at the visual sphere of the cerebral cortex.” – Reznö Bálint, 1907
You’re looking for a seat in a crowded theater; after scanning for awhile without success you eventually find an empty chair and sit down; the next day your friends ask you why you ignored them at the theater the night before, even though they were waving at you and you were looking right at them — what’s up with that? Neurologists tell us that our eyes pick up the information in the environment’s optical array and transmit the appropriate signals to the visual cortex, but somehow those waving friends in the theater don’t register in conscious perceptual awareness. It seems that the richness of our visual representation of the environment doesn’t match the richness of our visual experience of it. And so we fail to notice what’s right in front of our eyes.
Attention clearly has a lot to do with it. You can give someone a task that requires him to pay attention to some specific features of a dynamic scene, then introduce some unexpected event into the scene that’s unrelated to the task, and the person won’t notice that the event happened. Meanwhile, the intrusion of the strange event is obvious to other observers of the scene who aren’t engaged in the attention-demanding task. Even dramatic changes in the attended-to portions of the scene — like swapping the heads of two people in a photograph — go unnoticed if the change coincides precisely with the person blinking his eyes. Here’s a fun little study: the experimenter asks a passer-by for directions; as directions are being given, two other people carrying a wooden door walk between the experimenter and the passer-by; blocked from view, the experimenter changes places with someone else, who continues the conversation. Passers-by typically continued giving directions without recognizing the switch in who they were talking to.
“Inattentional blindness” impedes various aspects of visual perception: shape, size, color, motion. People do tend to notice certain kinds of unexpected and unattended-to visual objects: smiling faces, for example, or their own names printed out. Curiously, if the subject’s name is misspelled by only one letter, he tends not to notice the name at all. It seems that certain objects are more meaningful to observers than others, and that at some preconscious level the meaning draws visual attention to the object carrying the meaning. Similar studies performed on auditory stimuli confirm similar findings of “inattentional deafness.”
Here’s another example: I don’t know if the newfangled TV screens minimize glare, but mine doesn’t. If I’m watching a movie, I can selectively ignore the reflections bouncing onto the screen from the room and the window in which the TV is located, reflections that cover the entire field of view in which the movie is showing. If I’m not paying attention, just passing by, I can observe that the reflected light from the room might actually be brighter than the projected light of the movie. With attention it’s possible to ignore visual stimuli that completely overlap spatially with the object of visual attention. I can shift my attention from the movie to the reflection, but it’s hard to attend to both at the same time, even though the information for both is continuously and simultaneously on display in the environment and is being picked up by my visual sensory detection systems. This seems like Hitchcock territory: someone is watching a murder on a televised crime movie while, in the very same room, an actual murder is taking place, the murderer silently strangling the victim. The real murder is being reflected onto the TV screen without being noticed by the TV viewer, whose attention is fully captivated by the fake murder taking place in the movie.
A variety of studies have been conducted exploring inattentional blindness in simultaneous overlapping events, though to my knowledge the unnoticed murder experiment has never been systematically staged and documented in the scientific literature. Here’s one from 1975 that reminds me of Minority Report: The subject is shown a video in which two different ball games are being played simultaneously by two different groups of players. The subject is instructed to press a lever whenever a player in one of the games passes the ball to another player. About 30 seconds into the video a woman carrying an open umbrella walks onto the screen, traverses the entire visual field from right to left, then 4 seconds later walks out of the screen. The ball games continue for another 25 seconds, then the video ends. Fewer than a quarter of the subjects said that they’d noticed the umbrella-toting woman, even after they’d been asked specifically about her. When subjects simply watched the screen without being assigned the lever-pressing task, 100 percent of them noticed the umbrella-woman.
These sorts of experiments and findings went out of fashion for a couple of decades, not because they were debunked but because other research interests captured scientists’ attention. In recent years, however, the ball-playing experimental protocol has been varied systematically to see whether specific visual cues either exacerbate or override attentional blindness. E.g., what if the woman did a little dance while she was onscreen? what if a small boy carried the umbrella? what if a guy in a gorilla suit sans umbrella walked into the scene, stopping halfway across the screen to thump his chest? does the color of the costume worn by the anomalous passing figure make a difference?
Maybe the theoretical explanation is wrong. Maybe subjects actually noticed the anomalous walker but immediately forgot it to avoid getting distracted from the lever-pressing task. In other words, maybe what appears to be inattentional blindness is really a behavioral artifact of inattentional amnesia. A couple of variants in the experimental protocol were introduced to investigate the amnesia hypothesis. For example, what if the video ends with the umbrella-woman having traversed only halfway across the screen, such that the anomalous figure is still “visible” in the subject’s working memory of the scene? It turns out that subjects who report noticing the umbrella-woman often smile or laugh when she appears on the screen. Do subjects who don’t report seeing the umbrella when asked at the end of the video demonstrate similar visceral responses while she is on-screen?
By now you might be thinking: so what? This is pretty old-school experimental psychology, of passing interest at best to anyone but those nerds who specialize in this sort of fairly tedious empiricism. What strikes me though is the texture and complexity and nuance. With a sweep of the hand one can flatten the distinctions between a woman carrying an umbrella, a video projection of the umbrella-woman, a retinal image of the umbrella woman, and a conscious percept of the umbrella-woman. They’re all equally objects, we’re told; each of them, like all objects, is split between the sensual interactive component and the withdrawn essence; the relationship between their sensual components is one of translation, as is the case with all objects. How trivial and uninformative are such broad abstractions, it seems to me. A new theory, it is said, should be judged by the amount of work it creates. Here’s a potentially empirical question — which of these two theories is likely to generate more work: (1) a flat ontology of objects that all share the same characteristics and interactions, posited a priori; or (2) a multi-layered topography of objects whose diverse characteristics and interactions await discovery and explanation?
The kinds of studies I’ve mentioned here illustrate the failure of naïve realism: how we perceive the world isn’t necessarily how the world really is. But these studies also point to a way out: if we can understand the ways in which we misperceive, maybe we can compensate for our limitations, try again, and do better the next time.
[Many of the studies noted in this post are summarized in DJ Simons and CF Chabris, “Gorillas in our midst: sustained inattentional blindness for dynamic events — PDF]