Depth Cues Psychology

Imagine you're in a car and see a tree in the distance. How is it that the tree begins to look bigger as we drive closer? 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.

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

• We will start by looking 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.

Cues in Psychology

Cues in psychology are a stimulus, object or event that guides or influences behaviour.

Two types of cues that affect how we see things are monocular and binocular depth cues.

Monocular Depth Cues – Definition in Psychology

Monocular depth cues in psychology can be defined as:

Monocular Cues to Depth: Examples

There are many types of monocular depth cues, e.g.:

Binocular Depth Cues – Definition in Psychology

Binocular depth cues in psychology can be defined as:

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. Height in plane is an example of a monocular depth cue.

Let's discuss an example of height in plane to understand the concept better. Imagine a sheet of paper with a picture of two houses, with one placed higher than the other.

In this case, we would interpret the higher-up house as further away and the lower-down as closer.

Fig. 1. Height in plane is an example of a monocular depth cue.

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.

Fig. 2. Relative size is another example of a monocular depth cue.

Occlusion

This is when one object partially hides another object. The object in front overlapping the other is perceived to be closer than the partially hidden one.

Look at the monocular depth cues example below; the rectangle appears closer as it overlaps and partially hides the triangle.

Fig. 3. Occlusion is an example of a monocular depth cue.

Linear Perspective

This is when two parallel lines come together at some point in the horizon; the closer together the two lines are, the further away they seem.

A common example is a road that appears to converge in the distance. The closer the parallel lines appear to get, the further away it seems.

Fig. 4. Linear perspective is an example of a monocular depth cue.

Binocular Depth Cues – Types and Examples

There are two types of binocular depth cues, these are:

1. Convergence
2. Retinal disparity.

Convergence

To present images of what we see onto the retinas (the layer of tissue at the back of the eyes that sense light and transports images to the brain), the two eyes must rotate inwards toward each other. The closer an object is, the more the eyes must rotate.

The brain uses this information (amount of rotation) as a cue to construe how far away an object is. This works by detecting muscle differences the convergence causes in our eyes and analysing that information to decide the depth. It's a feedback tool, in a sense.

Retinal Disparity

When we see something, slightly different images of what we see are sent to each retina (as our eyes are apart, each eye sees things from a slightly different angle).

However, we don't view the world as a series of two images. This is because the brain processes the degree of difference or disparity between the two images and assembles one image for us that has depth, height, and width.

The disparity between the two images allows the brain to calculate how far away an object is. An object close to us has a large disparity, and an object far away has a small disparity.

Difference Between Monocular and Binocular Depth Cues

As the name suggests, binocular depth cues involve using both eyes, whereas monocular depth cues rely on one eye to process distance and depth perception.

Monocular depth cues allow us to see objects two-dimensionally, and binocular cues allow us to see objects in 3D.

The two types of cues are used to understand the depth and perception of objects in relation to our point of view; however, they use different processes. For example, binocular cues use retinal disparity and convergence, whereas monocular cues use height in plane, relative size, occlusion and linear perspective cues.