By Catherine A. Sanderson, Amherst College
Our mind organizes sensations into a perceptual gestalt, which means form or shape. This concept was studied first by so-called Gestalt psychologists in the early 20th century. They recognized that we automatically organize isolated objects we see in the world to form more cohesive wholes. The most fundamental Gestalt principle of organization is our ability to distinguish an object from its surroundings.
Grouping Based on Features
Gestalt principles of perceptual organization focus on how we automatically group stimuli together based on various features.
One such feature can be similarity—we group similar objects together. If a string of green dots tracing out a blocky back-and-forth pattern trails through a sea of blue dots, we may perceive a green number 5 because we automatically group the green dots together.
Another feature can be proximity. We tend to group objects that are near each other. So, if we see 18 hearts in a row, but some of the hearts are separated from each other by a couple of larger spaces, we may see three groups of hearts, not 18 separate hearts.
Continuity is one more feature we consider. We perceive continuous, smooth flowing lines even if dotted lines are actually drawn as jagged, broken lines.
The last feature is closure. We fill in gaps to perceive an object as a distinct whole, despite the gaps, meaning we give it closure in our minds.
This article comes directly from content in the video series Introduction to Psychology. Watch it now, on Wondrium.
Binocular Cues
Another way in which we organize what we see in the world is by estimating not just an object’s two-dimensional form (its height and width) but also its depth and how far it is away from us. This ability to perceive depth is innate and is seen even in young babies.
Our ability to see depth comes from several visual cues. First, we use binocular cues, meaning cues that rely on us having two eyes. One of these cues is known as retinal disparity, which refers to the slightly different images of the world the retinas on our two eyes receive about two and a half inches apart. When the brain then compares these two images, their differences help us figure out how far away we are from the object we are seeing.
The other binocular cue is known as convergence, meaning the extent to which our two eyes turn towards each other when we look at an object. If our two eyes turn towards each other a lot—say we are trying to look at a pencil we are holding just in front of our nose—then we know the object is very close. When our two eyes barely turn towards each other at all—say trying to look at a full moon—then we know the object is very far away.
Monocular Cues
We also rely on monocular cues, meaning cues that only rely on input from a single eye to perceive depth. These cues are regularly used by artists to indicate depth in paintings.
There’s a famous painting by Gustave Caillebotte of a rainy street in Paris which uses several monocular cues to create the illusion of depth. First, there’s interposition, meaning an object that is covering or blocking another object is perceived as closer. An umbrella held by a man walking with a woman blocks the pole of a streetlamp. The streetlamp is blocked, telling us that it is further away than the couple with the umbrella.
Next, there’s relative size. We know that people are all about the same size, so we understand that people who appear bigger are closer to us, and people who are smaller are further away.
Another monocular cue is known as relative height, meaning that objects that are higher on the horizon are seen as farther away. So, the artist paints some people not only smaller, but also higher up in the painting, and we perceive both their relative height and relatively small size as signaling that those people are further away.
Yet another monocular cue the artist is using is linear perspective, meaning that parallel lines appearing to converge as they get further away. The parallel lines indicating different floors of a building appear to come together as the lines recede into the distance.
Also, paintings can use a texture gradient, meaning surfaces appear rough up close, but smoother and less distinct as they get farther away. In the foreground cobblestones are clearly distinct and detailed, but they appear entirely smooth as they fade into the background.
When we leave the world of static paintings, another important monocular cue we use to determine depth is motion parallax or relative motion, meaning objects that are further away from us appear to be moving more slowly. We understand that when planes in the sky appear to be moving very slowly, that means they are very far away.
Perceptual Constancy
Another way in which we organize visual sensations from the world in a coherent way is by perceiving objects as stable, even when their appearance changes. Our adult brains automatically understand that the size of objects is constant.
This development of perceptual constancy means that we don’t see a coin flipped through the air as getting larger and smaller. We understand it has the same shape even if its shape appears to change as it rotates through the air.
Filmmakers often rely on our shape constancy to create visual illusions to make some people appear much smaller or larger than they actually are.
Thus, we realize that organizing sensory information from the world into coherent and meaningful units is obviously an important part of perception.
Common Questions about Perceptual Organization
Q: What is retinal disparity?
Our ability to see depth comes from several visual cues. One of these cues is known as retinal disparity, which refers to the slightly different images of the world the retinas on our two eyes receive about two and a half inches apart. When the brain then compares these two images, their differences help us figure out how far away we are from the object we are seeing.
Q: What is convergence?
Convergence is a binocular cue that helps us see depth. It refers to the extent to which our two eyes turn toward each other when we look at an object. If our two eyes turn toward each other a lot, then we know the object is very close.
Q: What is motion parallax?
Motion parallax or relative motion is a monocular cue we use to determine depth; objects that are further away from us appear to be moving more slowly.