New research from the Naval Medical Research Unit Dayton sheds light on the black hole illusion, a dangerous phenomenon — also known as the black hole effect or featureless terrain illusion — that affects pilots attempting to land at night.
The study, published in The International Journal of Aerospace Psychology, provides evidence that the illusion occurs because the human perceptual system attempts to recreate the horizon when a pilot cannot actually see it.
“The black hole illusion is one of the most commonly reported visual spatial disorientation illusions, and can lead to tragic consequences if the illusion is severe enough,” explained study author F. Eric Robinson, a research psychologist at the Naval Aerospace Medical Research Laboratory at Wright-Patterson Air Force Base.
“There is a relatively good understanding of the factors that make black hole illusions more likely, but there is not a definitive mechanistic explanation for the illusion itself. We, at NAMRU-Dayton, saw an opportunity to approach the black hole illusion in a new way in order to protect and enhance the readiness, performance, and survivability of naval and joint warfighters.”
Robinson and his colleagues hypothesized that a line bias illusion could explain why the black hole illusion occurs at night. They noted that “human vision is predisposed to creating a cohesive perceptual interpretation” and has been shown to “fill in” missing components of visual scenes. In the case of a pilot flying at night, this missing component is the horizon.
The researchers believe that pilots unconsciously estimate the position of the horizon based on the projected convergence point of runway edge lights. But since runway edge lines stop far short of their intersection at the horizon, it is unclear how accurate these estimates are.
In three experiments, which included 36 participants, the researchers examined how well people could estimate the intersection of angled line segments. The line segments consisted of white dots against a black background, similar to what a pilot would see on the final approach to the runway at night.
Robinson and his colleagues found that participants tended to misjudge the convergence point, indicating they would also misjudge the location of an implicit horizon based on runway lights. The misjudgment would cause an implicit horizon to be too low in the visual field, particularly early in the approach, which in turn could cause a pilot to adopt a low flight path.
“If our hypothesis is supported by future research, it would indicate that we have a strong tendency to rely on preferred spatial strategies even when some of the necessary information is missing. If our perceptual systems try to fill in the gaps, errors can occur. Basic perceptual mechanisms can have potentially profound effects on behavior,” Robinson told PsyPost.
Though the line segments used in the study resembled runway edge lights, they were not entirely representative of what a pilot would encounter at night. The researchers hope to use more realistic stimuli in future research examining the illusion.
“We found support for individual elements of our hypothesized explanation for black hole illusion. We are looking to do follow on research to further address the potential causal relationship between the line bias illusion and black hole illusion,” Robinson explained.
“We still need to replicate our findings using stimuli that better represent the aviation environment, specifically the runway sizes and line angles a pilot would see. We also need to test pilots in a flight simulator to see if the perceptual errors we observed actually affect performance and induce the black hole illusion.”
“NAMRU-Dayton conducts research at the highest levels of experimental and technical quality in order to best support the operational needs and requirements of our service members,” Robinson added. “NAMRU-Dayton’s unique set of human-rated acceleration devices allows us to maintain a technology base critical to Naval Aviation and federal and non-federal aerospace customers.
The study, “Preliminary Support for the Line Bias Illusion as a Contributor to Black Hole Effects“, was authored by F. Eric Robinson, Henry Williams, and Adam T. Biggs.