Psychotherapy Tips

Binocular depth cues psychology definition

Learn about the binocular cues for depth perception, and understand the meaning of binocular rivalry and retinal disparity through the binocular cues examples. Updated: 03/09/2022

Shannon has a Ed.D in curriculum and instruction from Oakland City University. She earned her Masters in building level administration from Oakland City University and her Bachelors of Science in biology from Marian University. Shannon transitioned to teaching over 11 years ago. She has experience teaching 6th-12th grade in the areas of general science, biology, and advanced biology.

What are the Binocular Cues for Depth Perception?

When one uses two eyes to see it is called binocular vision. With binocular vision, one can sense the depth of objects. Depth perception, or stereopsis, provides a relationship between the things one sees in their visual field, near or far. Each eye produces an image that is put together in the brain to create a three-dimensional image. These objects appear three-dimensional due to binocular depth cues.

When one looks at the image, they see the depth of the hearts toward the center of the image.

Depth Perception Image

There are two types of binocular depth cues: convergence and retinal disparity. Convergence uses both eyes to focus on the same object. As an object moves close, the eyes come closer together to focus. As the eye look at an object further away, the eyes move further apart to focus. Retinal disparity creates an overlapping image. Each eye produces an image; however, the angle of each eye is different, making the images different from each eye.

What is Binocular Convergence?

Proprioceptive senses rely on the five senses: touch, taste, smell, sight, and hearing. Proprioceptive senses are receptors in the body that help one experience the world around them. In the case of sight, it is binocular convergence.

Binocular convergence is when both eyes rotate inward at different angles to focus on an object. The degree to which the eyes turn is sent to the brain to determine how far away an object may be. Binocular convergence creates a three-dimensional image that helps with depth perception and the location of objects.

Retinal Disparity (Binocular Parallax)

Retinal disparity, or binocular parallax, is one’s sense of depth perception. Depth perception is possible due to each eye seeing at different angles. The eyes are approximately 6.3 centimeters apart, providing two different views of the same object and the environment. Retinal disparity exists in organisms with two eyes that are directed toward the front.

To observe retinal disparity, cover one eye and look at an object, observe the location of the object. Cover the other eye and view the same object, paying attention again to the location of the object. The two different eyes view the same object to exist in different places.

Imagine you’re in a car and you see a tree in the distance. How is it that as we drive closer the tree begins to look bigger? Trees obviously aren’t growing. So what is causing this? I’ll give you a hint… it’s our brain and eyes using depth cues. Depth perception refers to the ability to see the world in 3D and judge how far away/close objects are from and to us. This judgement is very important for navigating everyday life. How we move from one point to another relies quite heavily on our ability to perceive depth, and even picking up an object, such as your pencil, relies on the ability to judge depth.

For example, if we were crossing the road and couldn’t judge how far away a car was, it would be a bit of a disaster.

Let’s take a look at depth cues in psychology!

  • We will start by taking a look at monocular depth cues definition psychology and binocular depth cues psychology.
  • We will then move on to look at monocular depth cues examples whilst exploring aspects such as height in plane, relative size, occlusion and linear perspective.
  • Moving along to do the same and looking at binocular depth cues examples, focusing on convergence and retinal disparity.
  • Finally, we will highlight the difference between monocular and binocular depth cues.

Monocular Depth Cues – Definition in Psychology

Monocular depth cues in psychology can be defined as:

Monocular depth cues: information about the depth that can be judged using only one eye. Monocular depth cues can be used in pictures, so a lot of monocular depth cues are used in art to give viewers a sense of depth.

Binocular Depth Cues – Definition in Psychology

Binocular depth cues in psychology can be defined as:

Binocular depth cues: information about depth that uses both eyes to see and understand 3D space; this is a lot easier for our brains to comprehend than monocular depth cues.

The difference between monocular and binocular depth cues is that monocular depth cues use one eye to judge depth, and binocular depth cues use both eyes to perceive depth.

Monocular Depth Cues – Types and Examples

There are four monocular depth cues you will need to know for GCSE psychology. These are:

  1. Height in plane
  2. Relative size
  3. Occlusion
  4. Linear perspective.

Height in plane

Height in plane is when objects placed higher up appear or would be interpreted as further away. Have a look at the monocular depth cues example below, note that the house that is placed higher would be interpreted as being further away from us, and the house lower down would be seen as being closer to us.

Depth Cues Psychology houses height in plane StudySmarterExample of height in plane, Erika Hae, StudySmarter Originals

Relative size

If there are two objects that are the same size (e.g., two trees of the same size), the object that is closer will look larger. Have a look at the monocular depth cues example below, tree number 1 seems closer because it is larger, and tree number 2 seems further away because it is smaller.

Depth Cues Psychology trees relative size StudySmarterExample of relative size, Erika Hae, StudySmarter Originals

Occlusion

This is when one object partially hides another object. The object in front that is overlapping the other is perceived to be closer than the one that is being partially hidden. Look at the monocular depth cues example below; the rectangle appears closer as it overlaps and partially hides the triangle.

Retinal Disparity

Retinal disparity, also known as binocular parallax, refers to the fact that our eyes are about 6.3 centimeters apart on our face on average and, as a result, each sees the world from a slightly different angle. You can test this by extending your pointer finger at arm’s length and alternating opening and closing your eyes. You’ll notice that, as you do this, your finger seems to shift depending on which eye you’re looking through.

Retinal disparity may seem like a cool parlor trick, but how does it actually work to give you a sense of depth perception? Well, the different angles that your right and left eyes see an object from actually enable you to see more of the object itself. You’re literally seeing the same object but from a slightly different perspective; thus, you’re taking in slightly different information about the size, shape, positioning, and contours of an object. Your brain takes these slightly different views and integrates them into a three-dimensional image of the object.

Have you ever viewed a ‘Magic Eye’ image? They appear like a random series of dots or shapes until your eyes adjust and then, bam, a 3D image appears. These types of images are known as autostereograms because they are a 3D (‘stereo’, for stereopsis) image (‘gram’) that your eyes find automatically (‘auto’) without the need of any special viewing tool. They actually rely on your retinal disparity to reconstruct the sense that a three-dimensional object is hidden in the image. They’re created by superimposing two images, one of the object as would be seen by your left eye and one of the same object as would be seen by your right eye. Once you find the right focal distance, the hidden image seems to magically pop out of nowhere because each eye is provided with the appropriate angle of the object as if it were a real 3D object sitting before you.

Binocular Convergence

Binocular convergence is the other binocular cue that enables your sense of depth perception. It refers to the physiological angles that each of your eyes needs to rotate to focus on any given object. It’s what’s known as a proprioceptive sense (meaning a sense of one’s own self) in that it uses feedback information from the muscles of your eyes to understand your eyes’ rotation in their sockets and, as a result, the distance the object is from you.

Ok, so what does that even mean? Well, let’s repeat the test from above, except this time extend your pointer finger at arm’s length and, while keeping both eyes open, draw your finger towards your face. You’ll notice that at a certain point, the muscles in your eyes strain due to the degree of your eye-cross, and the single image of your finger diverges into two. If you do this test in reverse (starting at your nose, draw your finger out), at a certain point the two images of your finger will converge into one. In other words, binocular convergence is the phenomenon where your eyes rotate inwards to focus on an object, and the degree to which they rotate indicates to your brain how near or far an object is – nearer objects require a greater degree of inward rotation than objects farther from your face.

Lesson Summary

Binocular cues are visual information taken in by two eyes that enable us a sense of depth perception, or stereopsis. Retinal disparity, also known as binocular parallax, refers to the fact that each of our eyes sees the world from a slightly different angle. Binocular convergence, on the other hand, is a proprioceptive sense using feedback information from the muscles of your eyes to understand your eyes’ rotation in their sockets and, as a result, the distance the object is from you.

Learning Outcomes

As you come to the end of the lesson, you should make a goal to:

  • Define what binocular clues are
  • Explain depth perception
  • Discuss retinal disparity and how it enables depth perception
  • Understand how autostereograms work
  • Consider what binocular convergence is and its role in depth perception

Binocular Depth Cues

Properties of the visual system that facilitate depth perception by the nature of messages that are sent to the brain.

Binocular depth cues are based on the simple fact that a person’s eyes are located in different places. One cue, binocular disparity, refers to the fact that different optical images are produced on the retinas of both eyes when viewing an object. By processing information about the degree of disparity between the images it receives, the brain produces the impression of a single object that has depth in addition to height and width.

The second cue, called binocular convergence, is based on the fact that in order to project images on the retinas, the two eyes must rotate inward toward each other. The closer the perceived object is, the more they must rotate, so the brain uses the information it receives about the degree of rotation as a cue to interpret the distance of the perceived objects. Yet another cue to depth perception is called binocular accommodation, a term that refers to the fact that the lens of the eye changes shape when it brings an image into focus on the retina. The muscular activity necessary for this accommodation acts as a signal for the brain to generate perception of depth and distance.

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