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The Visual Illusions that Reveal How Our Minds Work

Illusions in Disney parks display how our minds make sense of the world.

Key points

  • Multiple effects in The Haunted Mansion use low-tech illusions that exploit our visual system's tendency to make assumptions.
  • Castles at Disney parks look taller than they are because they trick the cues we use to judge distance.
  • So-called "dark" rides succeed in part because riders fill in with their own minds what they cannot see.

Our visual system is constantly making assumptions about what we see. In one of my first psychology courses in college, our professor used an effect from Disney's classic Haunted Mansion attraction to demonstrate the point. The effect, shown below, is sometimes called the staring bust.

As you walk by these faces, they seem to follow you wherever you go, even though they clearly aren't really moving. The effect is unsettling.

I was reminded of this experience while watching Behind the Attraction, a 10-part Disney+ series about the history and design of some of the most iconic Disney attractions. Each episode of the series, released earlier this year, focuses on one attraction, like The Haunted Mansion, Jungle Cruise, or "it's a small world". Some episodes rehash material from the 2019 documentary The Imagineering Story (also on Disney+), but while The Imagineering Story had a serious, historical tone and told a largely chronological story over several episodes, Behind the Attraction episodes are stand-alone, and the series has an irreverent tone with a jumpy style.

The surprisingly low-tech illusions in The Haunted Mansion

So how does the staring bust work? Not through any high-tech tricks or mechanics. It simply relies on how our minds interpret what we see.

The basic trick is that the busts are concave (they are essentially inverted faces) and the light is shining from below. A concave object lit from below creates shading identical to a convex object lit from above, which explains why these faces look like they are pointed outward. But why do they seem to follow us around? Because we don't know where the light is coming from and, by default, we assume it's coming from above. Given this assumption, and the unusual shape of the faces, no matter where we stand, the shading will create the impression that it is facing us.

Why do we make this assumption? Probably because that usually is where the light is coming from —the sun outdoors, ceiling lights indoors. And as is often the case with perception, without context, we make assumptions. Without such assumptions, the amount of information bombarding us every moment would be overwhelming and confusing. But assumptions can be wrong, and they can be deliberately fooled, as with the staring busts.

The Pepper's Ghosts of The Haunted Mansion

The Haunted Mansion episode of Behind the Attraction highlights another simple but effective illusion: the translucent ghosts in the ballroom scene of the attraction.

Offspring_Fan6923/Flickr
The Haunted Mansion ballroom.
Source: Offspring_Fan6923/Flickr

This illusion, known as Pepper’s Ghost, dates to the 19th century and is named for a British scientist. In The Haunted Mansion, it works like this. Underneath and above riders are animatronics carefully positioned to replicate the ghosts' placement in the ballroom. The ghostly images are created by lighting the figures through a plate of glass separating the figures from the actual room. What riders see are actually just reflections, the same way things might appear when you look out the window at night while a lamp is on indoors. But just as with the staring busts, we readily accept the illusion because there’s no obvious explanation for it: The glass and lights are all hidden from view.

What Disney's castles reveal about how we perceive depth

One episode of Behind the Attraction focuses on Disney's castles. In the episode, Disney's Imagineers describe a trick, called forced perspective, that creates the illusion that the structure is taller than it is.

Skylar Sahakian/Unsplash
Sleeping Beauty Castle at Disneyland in California.
Source: Skylar Sahakian/Unsplash

The pieces at each level of the castle are a little smaller than those at the level below, exploiting several cues our visual system uses for judging distance. First is linear perspective: As things recede into the distance, lines converge at a vanishing point. So, when you're standing at the base of the castle, looking up, the increasingly smaller levels make it appear as if the edges of the castle are receding more quickly than their true distance would indicate. Our visual system interprets the top of the castle as being further away than it is.

But when you’re standing far away from the castle, looking at it straight on, this linear perspective effect doesn't work. Yet the forced perspective trick still works, due to another, more subtle distance cue we rely on.

To illustrate, imagine you see two mugs apparently next to each other, one appearing to be one-tenth the size of the other. It could be that the smaller mug is a dollhouse mug, or it could be that the smaller mug is positioned far behind the larger mug. This illustrates how we sometimes use the relative size of familiar objects as a cue for where they are in space. When we look at the Disney castles, we assume the features at all levels are the same size, just as they normally are in all the buildings we have seen before. But because the features in the Disney castle are actually shrinking in size, we perceive them as further away.

The power of imagination

Classic attractions like The Haunted Mansion and Pirates of the Caribbean are known as dark rides because they are entirely indoors with illuminated show scenes. The "dark" in dark rides is essential and key to creating the greatest illusion of all: the illusion of completeness.

Disney's attention to detail is unmatched, which is why it's possible to ride an attraction a dozen times and still notice something new. But you rarely think about what you can't see—everything that's shrouded in darkness or hidden from view. If we could see these areas, the illusion would be broken because, at best, there's nothing there; at worst, it's a bunch of filth, tangled wires, and uninviting electronic and mechanical equipment.

The fact is, we usually only see only small parts of scenes, just enough to trigger our imaginations, and we fill in the rest with our minds. This happens automatically, because our visual systems do this constantly when presented with incomplete and noisy information. We have to make guesses and inferences, usually without even realizing we're doing it. Usually, those guesses involve extrapolating from what we can see.

Disney Imagineers have taken advantage of this human trait to full effect. They show us something incredible, but just enough so that we mentally complete the scene with ideas more fantastical than even they could create.

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