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Monocular depth cues of interposition psychology definition

Take a look at these triangles. This image contains an example of an interposition.

Which of the two triangles in this picture do you think is the closest to you? Which one do you think is further away?

We all know what a triangle looks like. It has three corners and three sides. You can see the full green triangle, but the red triangle is partially covered. We would judge the green triangle as being closer and the red triangle as being further away, though in reality, both triangles are the same distance from you as measured by the distance between your eyes and the screen. It is the overlap that causes you to perceive depth in this image.

Now, look at these circles.


Which one of the circles is closest to you? Because we know what circles look like and we only see part of the yellow circle, we judge the blue circle as being closer.

Now see if you can tell how far the circles are away from each other. It is impossible to tell the distance between the two circles. That is because interposition only gives us information on the depth of the circles in relation to each other. Interposition provides no information regarding the absolute depth.

Lesson Summary

Interposition is a monocular cue that occurs when one object obscures another, which causes the object that is partially covered to appear more distant. Because we only see part of what we expect, we interpret the object that is partially covered as being further away. The major assumption of interposition is that near objects always at least partially overlap objects that are further away.

Learning Outcomes

As you finish this lesson, your goal should be to:

  • Remember what interposition is
  • Compare monocular and binocular cues
  • Examine examples of interposition

Monocular cues play a huge role in how you perceive the world around you. Keep reading to learn how different types of monocular cues help you interpret and understand what you’re seeing.

The word “monocular” means “with one eye.” Monocular cues are all the ways that a single eye helps you see and process what you’re looking at.

Vrotsos also said that “visual information, as seen with a single eye, can detect an object moving at a distance, but can’t necessarily decipher the entire scene.”

“With monocular cues, images are interpreted as two-dimensional. Think of a painting that gives the illusion of depth by playing with the foreground and background. That is your eye and monocular cues in the real world — things that are closer are larger and move faster; things in the background are smaller and move slower.”

Monocular cues refer to the ways that each of your eyes takes in visual information that’s used to judge:

Now, let’s get into the six main subcategories of monocular cues that contribute to your vision.

Relative size

This monocular cue gives you the ability to measure how far away something is. It works by judging how big or small the object is and what that means in relation to other objects you’ve interacted with in the past.

Here’s an example: When you see a plane fly by in the sky above you, it looks really small. But you probably know that up close, a plane is huge.

What this means is that your vision (the plane you see in the sky) connects with your memory (a plane you’ve seen up close) to indicate to you that because the plane looks so small, it must be extremely far away.


Interposition refers to what happens when two objects on a flat surface, like a drawing of two circles, look like they have some relation to each other in terms of distance, even when they’re not actually in 3-D space.

Here’s a longer explanation of the classic circles example: Let’s say you have two circles drawn next to each other on a piece of paper. In this case, both circles will appear to have the same depth.

But let’s say you then draw the circles so that they intersect with one another (kind of like a Venn diagram). If you color in one of the circles, it’ll look like it’s overlapping the other circle.

Your eye will then perceive that the overlapping circle is closer to or on top of the other circle. Now the circles will appear to have depth even though they’re still just 2-D drawings on a flat piece of paper.

Linear perspective

Linear perspective happens when the angles of two adjacent objects and the distance between them look smaller and smaller. This causes your eye to interpret those objects as increasingly farther away from you.

For example, imagine you’re drawing a road or train tracks extending into the distance. You might start drawing each side of the road or tracks at the bottom of your piece of paper.

As you continue to draw the road or tracks moving “away” from you, the lines might angle closer together toward the center of the paper. This will result in a triangular shape.

As you look at the triangle, the closer you get to its tip, the farther away your eye will interpret the road or tracks to be from your position. This is due to the angle of the lines and the fact that they’re closer together at the tip than where they start at the bottom of your piece of paper.

Aerial perspective

Aerial perspective is what makes far away objects look a bit blurrier, lighter in color, and less detailed than those closer to you.

Think about mountains off in the distance. They tend to be much lighter in shade and color than a mountain that’s much closer to you.

This happens because blue light scatters into the air when it interacts with the atmosphere — which often makes distant objects appear light blue.

Contrast of color also plays a role in aerial perspective.

Objects that are farther away tend to have rough, blurry edges because of the scattered light in the air, and colors tend to blur together. Closer objects, on the other hand, have more defined edges and a starker contrast of color.

Big objects, like mountains and skyscrapers, seem bigger and clearer when the air is clean because there are fewer particles to scatter the light.

Light and shade

The way that light hits an object creates shades of light and dark. This tells your eyes where an object sits in relation to the light and to objects nearby.

This cue can also tell you if something is upside down because the light source will hit the object differently, so that it visually contrasts with other parts of your environment.

Monocular motion parallax

This one’s a mindblower. The monocular motion parallax happens when you move your head and objects that are farther away appear to move at a different speed than those closer to you.

Try it out by looking at something far away. Then, slowly turn your head from left to right and back again.

You may notice that objects nearer to you appear to be moving in the opposite direction of the way your head is going. But objects farther away from you seem to follow the direction of your head.

Interposition Psychology

Interposition Psychology Definition

According to an Oxford Dictionary, “Interposition Psychology” is the placement of monocular cues of visual depth perception and overlapping another object. The overlapping object looks closer than the monocular cue, which is the backend. When one object blocks the path of another, the blocked object is perceived as more distant. 

Interposition is the act of overlapping two objects to give the illusion of depth. Interposition is one of the Monocular Cues For Depth Perception. Monocular cues are formed when one object partially covers another, known as interposition or overlapping. By doing so, it appears as if the object that is being covered is the one that is further away. Any stimulus related to depth perception which can be perceived with one eye alone is a monocular cue. As opposed to binocular cues, in which the depth is perceived by using both eyes at the same time.

Interposition Psychology Example

Interposition Psychology Example

Look at these two triangles, Green and Red. The green triangle is fully visible, but the red triangle is partially hidden. Green triangles appear closer and red triangles appear further away, despite the fact that, as measured by the distance between your eyes and the screen, both triangles are at the same distance from you. In this image, it is the overlap that gives the impression of depth.

Depth Perception

Depth perception is the ability to perceive the world in three dimensions (3D) and to judge the distance of objects. Your brain creates 3D images by combining images from each eye and combining them to form one image. Your eyes are able to determine the distance between objects, as well as whether something is far away or close to you, by depth perception.

A variety of depth cues contribute to depth perception. They can be categorized as binocular cues to represent information received from both eyes in three dimensions, and monocular cues to represent information received in only two dimensions and observed by only one eye.

Monocular Cues For Depth Perception 

  • Interposition

  • Linear Perspective

  • Aerial Perspective

  • Retinal Image

  • Texture Gradient

  • Shading

  • Movement Cues

  • Accommodation

Binocular Cues For Depth Perception 

  • Convergence

  • Retinal disparity


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