Introducing the Perception Process

Perception is the set of unconscious processes we undergo to make sense of the stimuli and sensations we encounter.

Introduction to Perception

Perception refers to the set of processes we use to make sense of all the stimuli you  encounter every second, from the glow of the computer screen in front of you to the smell of the room to the itch on your ankle. Our perceptions are based on how we interpret all these different sensations, which are sensory impressions we get from the stimuli in the world around us. Perception enables us to navigate the world and to make decisions about everything, from which T-shirt to wear or how fast to run away from a bear.

Close your eyes. What do you remember about the room you are in? The color of the walls, the angle of the shadows? Whether or not we know it, we selectively attend to different things in our environment. Our brains simply don’t have the capacity to attend to every single detail in the world around us. Optical illusions highlight this tendency. Have you ever looked at an optical illusion and seen one thing, while a friend sees something completely different? Our brains engage in a three-step process when presented with stimuli: selection, organization, and interpretation.

For example, think of Rubin’s Vase, a well-known optical illusion depicted below. First we select the item to attend to and block out most of everything else. It’s our brain’s way of focusing on the task at hand to give it our attention. In this case, we have chosen to attend to the image. Then, we organize the elements in our brain. Some individuals organize the dark parts of the image as the foreground and the light parts as the background, while others have the opposite interpretation.

Rubin’s Vase: Rubin’s Vase is a popular optical illusion used to illustrate differences in perception of stimuli.

Some individuals see a vase because they attend to the black part of the image, while some individuals see two faces because they attend to the white parts of the image. Most people can see both, but only one at a time, depending on the processes described above. All stages of the perception process often happen unconsciously and in less than a second.

The Perception Process

The perceptual process is a sequence of steps that begins with stimuli in the environment and ends with our interpretation of those stimuli. This process is typically unconscious and happens hundreds of thousands of times a day. An unconscious process is simply one that happens without awareness or intention. When you open your eyes, you do not need to tell your brain to interpret the light falling onto your retinas from the object in front of you as “computer” because this has happened unconsciously. When you step out into a chilly night, your brain does not need to be told “cold” because the stimuli trigger the processes and categories automatically.

Selection

The world around us is filled with an infinite number of stimuli that we might attend to, but our brains do not have the resources to pay attention to everything. Thus, the first step of perception is the (usually unconscious, but sometimes intentional) decision of what to attend to. Depending on the environment, and depending on us as individuals, we might focus on a familiar stimulus or something new. When we attend to one specific thing in our environment—whether it is a smell, a feeling, a sound, or something else entirely—it becomes the attended stimulus.

Organization

Once we have chosen to attend to a stimulus in the environment (consciously or unconsciously, though usually the latter), the choice sets off a series of reactions in our brain. This neural process starts with the activation of our sensory receptors (touch, taste, smell, sight, and hearing). The receptors transduce the input energy into neural activity, which is transmitted to our brains, where we construct a mental representation of the stimulus (or, in most cases, the multiple related stimuli) called a percept. An ambiguous stimulus may be translated into multiple percepts, experienced randomly, one at a time, in what is called “multistable perception.”

Interpretation

After we have attended to a stimulus, and our brains have received and organized the information, we interpret it in a way that makes sense using our existing information about the world. Interpretation simply means that we take the information that we have sensed and organized and turn it into something that we can categorize. For instance, in the Rubin’s Vase illusion mentioned earlier, some individuals will interpret the sensory information as “vase,” while some will interpret it as “faces.” This happens unconsciously thousands of times a day. By putting different stimuli into categories, we can better understand and react to the world around us.

Duck or Rabbit?: In this famous optical illusion, your interpretation of this image as a duck or a rabbit depends on how you organize the information that you attend to.

Selection

Selection, the first stage of perception, is the process through which we attend to some stimuli in our environment and not others.

Most of us are presented with millions of sensory stimuli a day. How do we know what to attend to and what to ignore? What tells us that it’s okay not to notice each and every leaf on each and every tree that we pass, but important to attend to the dip in the sidewalk in front of us? Though perception is different for each person, we each attend to the stimuli that are meaningful in our individual worlds. Selection is the process by which we attend to some stimuli in our environment and not others. Because we cannot possibly attend to all of the stimuli we are presented with, our brains have an amazing unconscious capacity to pick and choose what’s important and what’s not.

The Influence of Motives

Motivation has an enormous impact on the perceptions people form about the world. A simple example comes from a short-term drive, like hunger: the smell of cooking food will catch the attention of a person who hasn’t eaten for several hours, while a person who is full might not attend to that detail. Long-term motivations also influence what stimuli we attend to. For example, an art historian who has spent many years looking at visual art might be more likely to pay attention to the detailed carvings on the outside of a building; an architect might be more likely to notice the structure of the columns supporting the building.

Perceptual expectancy, also called perceptual set, is a predisposition to perceive things in a certain way based on expectations and assumptions about the world. A simple demonstration of perceptual expectancy involves very brief presentations of non-words such as “sael.” Subjects who were told to expect words about animals read it as “seal,” but others who were expecting boat-related words read it as “sail.”

Emotional drives can also influence the selective attention humans pay to stimuli. Some examples of this phenomenon are:

• Selective retention: recalling only what reinforces your beliefs, values, and expectations. For example, if you are a fan of a particular basketball team, you are more likely to remember statistics about that team than other teams that you don’t care about.
• Selective perception: the tendency to perceive what you want to. To continue the basketball team example, you might be more likely to perceive a referee who makes a call against your favorite team as being wrong because you want to believe that your team is perfect.
• Selective exposure: you select what you want to expose yourself to based on your beliefs, values, and expectations. For example, you might associate more with people who are also fans of your favorite basketball team, thus limiting your exposure to other stimuli. This is commonly seen in individuals who associate with a political party or religion: they tend to spend time with others who reinforce their beliefs.

The Cocktail Party Effect

Selective attention shows up across all ages. Babies begin to turn their heads toward a sound that is familiar to them, such as their parents’ voices. This shows that infants selectively attend to specific stimuli in their environment. Their accuracy in noticing these physical differences amid background noise improves over time.

Some examples of messages that catch people’s attention include personal names and taboo words. The ability to selectively attend to one’s own name has been found in infants as young as 5 months of age and appears to be fully developed by 13 months. This is known as the ” cocktail party effect.” (This term can also be used generally to describe the ability of people to attend to one conversation while tuning out others.)

Cocktail Party Effect: One will selectively attend to their name being spoken in a crowded room, even if they were not listening for it to begin with.

The Influence of Stimulus Intensity

A stimulus that is particularly intense, like a bright light or bright color, a loud sound, a strong odor, a spicy taste, or a painful contact, is most likely to catch your attention. Evolutionary psychologists theorize that we selectively attend to these kinds of stimuli for survival purposes. Humans who could attend closely to these stimuli were more likely to survive than their counterparts, since some intense stimuli (like pain, powerful smells, or loud noises) can indicate danger. More than half the brain is devoted to processing sensory information, and the brain itself consumes roughly one-fourth of one’s metabolic resources, so the senses must provide exceptional benefits to fitness.

Organization

Organization is the stage in the perception process in which we mentally arrange stimuli into meaningful and comprehensible patterns.

After the brain has decided which of the millions of stimuli it will attend to, it needs to organize the information that it has taken in. Organization is the process by which we mentally arrange the information we’ve just attended to in order to make sense of it; we turn it into meaningful and digestible patterns. Below is a discussion of some of the different ways we organize stimuli.

Gestalt Laws of Grouping

The Gestalt laws of grouping is a set of principles in psychology first proposed by Gestalt psychologists to explain how humans naturally perceive stimuli as organized patterns and objects. Gestalt psychology tries to understand the laws of our ability to acquire and maintain meaningful perceptions in an apparently chaotic world. The central principle of gestalt psychology is that the mind forms a global whole with self-organizing tendencies. The gestalt effect is the capability of our brain to generate whole forms, particularly with respect to the visual recognition of global figures, instead of just collections of simpler and unrelated elements. Essentially, gestalt psychology says that our brain groups elements together whenever possible instead of keeping them as separate elements.

A few of these laws of grouping include the laws of proximity, similarity, and closure and the figure-ground law.

The Law of Proximity

This law posits that when we perceive a collection of objects we will perceptually group together objects that are physically close to each other. This allows for the grouping together of elements into larger sets, and reduces the need to process a larger number of smaller stimuli. For this reason, people tend to see clusters of dots on a page instead of a large number of individual dots. The brain groups together the elements instead of processing a large number of smaller stimuli, allowing us to understand and conceptualize information more quickly.

Gestalt law of proximity: Because of the law of proximity, people tend to see clusters of dots on a page instead of a large number of individual dots.

The Law of Similarity

This law states that people will perceive similar elements will be perceptually grouped together. This allows us to distinguish between adjacent and overlapping objects based on their visual texture and resemblance.

The law of similarity: Because of the law of similarity, people tend to see this as six clusters of black and white dots rather than 36 individual dots.

The Figure-Ground Law

A visual field can be separated into two distinct regions: the figures (prominent objects) and the ground (the objects that recede into the background. Many optical illusions play on this perceptual tendency.

The figure-ground law: In the Kanizsa triangle illusion, the figure-ground law causes most people to perceive a white triangle in the foreground, which makes the black shapes recede into the background.

The Law of Closure

The law of closure explains that our perception will complete incomplete objects, such as the lines of the IBM logo.

IBM logo: The IBM logo plays on the law of closure. While it is made up of just lines, we perceive the three letters.

Organizing People

Human and animal brains are structured in a modular way, with different areas processing different kinds of sensory information. A special part of our brain known as the fusiform face area (FFA) is dedicated to the recognition and organization of people. This module developed in response to our need as humans to recognize and organize people into different categories to help us survive.

Perceptual Schemas

We develop perceptual schemas in order to organize impressions of people based on their appearance, social roles, interaction, or other traits; these schemas then influence how we perceive other things in the world. These schemas are heuristics, or shortcuts that save time and effort on computation. For example, you might have a perceptual schema that the building where you go to class is symmetrical on the outside (sometimes called the “symmetry heuristic,” or the tendency to remember things as being more symmetrical than they are). Even if it isn’t, making that assumption saved your mind some time. This is the blessing and curse of schemas and heuristics: they are useful for making sense of a complex world, but they can be inaccurate.

Stereotypes

We also develop stereotypes to help us make sense of the world. Stereotypes are categories of objects or people that help to simplify and systematize information so the information is easier to be identified, recalled, predicted, and reacted to. Between stereotypes, objects or people are as different from each other as possible. Within stereotypes, objects or people are as similar to each other as possible.

While our tendency to group stimuli together helps us to organize our sensations quickly and efficiently, it can also lead to misguided perceptions. Stereotypes become dangerous when they no longer reflect reality, or when they attribute certain characteristics to entire groups. They can contribute to bias, discriminatory behavior, and oppression.

Interpretation

Interpretation, the final stage of perception, is the subjective process through which we represent and understand stimuli.

In the interpretation stage of perception, we attach meaning to stimuli. Each stimulus or group of stimuli can be interpreted in many different ways. Interpretation refers to the process by which we represent and understand stimuli that affect us. Our interpretations are subjective and based on personal factors. It is in this final stage of the perception process that individuals most directly display their subjective views of the world around them.

Factors that Influence Interpretation

Cultural values, needs, beliefs, experiences, expectations, involvement, self-concept, and other personal influences all have tremendous bearing on how we interpret stimuli in our environment.

Experiences

Prior experience plays a major role in the way a person interprets stimuli. For example, an individual who has experienced abuse might see someone raise their hand and flinch, expecting to be hit. That is their interpretation of the stimulus (a raised hand). Someone who has not experienced abuse but has played sports, however, might see this stimulus as a signal for a high five. Different individuals react differently to the same stimuli, depending on their prior experience of that stimuli.

Values and Culture

Culture provides structure, guidelines, expectations, and rules to help people understand and interpret behaviors. Ethnographic studies suggest there are cultural differences in social understanding, interpretation, and response to behavior and emotion. Cultural scripts dictate how positive and negative stimuli should be interpreted. For example, ethnographic accounts suggest that American mothers generally think that it is important to focus on their children’s successes while Chinese mothers tend to think it is more important to provide discipline for their children. Therefore, a Chinese mother might interpret a good grade on her child’s test (stimulus) as her child having guessed on most of the questions (interpretation) and therefore as worthy of discipline, while an American mother will interpret her child as being very smart and worthy of praise. Another example is that Eastern cultures typically perceive successes as being arrived at by a group effort, while Western cultures like to attribute successes to individuals.

Expectation and Desire

An individual’s hopes and expectations about a stimulus can affect their interpretation of it. In one experiment, students were allocated to pleasant or unpleasant tasks by a computer. They were told that either a number or a letter would flash on the screen to say whether they were going to taste orange juice or an unpleasant-tasting health drink. In fact, an ambiguous figure (stimulus) was flashed on screen, which could either be read as the letter B or the number 13 (interpretation). When the letters were associated with the pleasant task, subjects were more likely to perceive a letter B, and when letters were associated with the unpleasant task they tended to perceive a number 13. The individuals’ desire to avoid the unpleasant drink led them to interpret a stimulus in a particular way.

Similarly, a classic psychological experiment showed slower reaction times and less accurate answers when a deck of playing cards reversed the color of the suit symbol for some cards (e.g. red spades and black hearts). Peoples’ expectations about the stimulus (“if it’s red, it must be diamonds or hearts”) affected their ability to accurately interpret it.

Self-concept

This term describes the collection of beliefs people have about themselves, including elements such as intelligence, gender roles, sexuality, racial identity, and many others. If I believe myself to be an attractive person, I might interpret stares from strangers (stimulus) as admiration (interpretation). However, if I believe that I am unattractive, I might interpret those same stares as negative judgments.

Perceptual Constancy

Perceptual constancy is perceiving objects as having constant shape, size, and color regardless of changes in perspective, distance, and lighting.

Have you ever noticed how snow looks just as “white” in the middle of the night under dim moonlight as it does during the day under the bright sun? When you walk away from an object, have you noticed how the object gets smaller in your visual field, yet you know that it actually has not changed in size? Thanks to perceptual constancy, we have stable perceptions of an object’s qualities even under changing circumstances.

Perceptual constancy is the tendency to see familiar objects as having standard shape, size, color, or location, regardless of changes in the angle of perspective, distance, or lighting. The impression tends to conform to the object as it is assumed to be, rather than to the actual stimulus presented to the eye. Perceptual constancy is responsible for the ability to identify objects under various conditions by taking these conditions into account during mental reconstitution of the image.

Even though the retinal image of a receding automobile shrinks in size, a person with normal experience perceives the size of the object to remain constant. One of the most impressive features of perception is the tendency of objects to appear stable despite their continually changing features: we have stable perceptions despite unstable stimuli. Such matches between the object as it is perceived and the object as it is understood to actually exist are called perceptual constancies.

Visual Perceptual Constancies

There are many common visual and perceptual constancies that we experience during the perception process.

Size Constancy

Within a certain range, people’s perception of a particular object’s size will not change, regardless of changes in distance or size change on the retina. The perception of the image is still based upon the actual size of the perceptual characteristics. The visual perception of size constancy has given rise to many optical illusions.

The Ponzo illusion: This famous optical illusion uses size constancy to trick us into thinking the top yellow line is longer than the bottom; they are actually the exact same length.

Shape Constancy

Regardless of changes to an object’s orientation, the shape of the object as it is perceived is constant. Or, perhaps more accurately, the actual shape of the object is sensed by the eye as changing but then perceived by the brain as the same. This happens when we watch a door open: the actual image on our retinas is different each time the door swings in either direction, but we perceive it as being the same door made of the same shapes.

Shape constancy: This form of perceptual constancy allows us to perceive that the door is made of the same shapes despite different images being delivered to our retinae.

Distance Constancy

This refers to the relationship between apparent distance and physical distance. An example of this illusion in daily life is the moon. When it is near the horizon, it is perceived as closer to Earth than when it is directly overhead.

Color Constancy

This is a feature of the human color perception system that ensures that the color of an object remains similar under varying conditions. Consider the shade illusion: our perception of how colors are affected by bright light versus shade causes us to perceive the two squares as different colors. In fact, they are the same exact shade of gray.

Checker-shadow illusion: Color constancy tricks our brains into seeing squares A and B as two different colors; however, they are the exact same shade of gray.

Auditory Perceptual Constancies

Our eyes aren’t the only sensory organs that “trick” us into perceptual constancy. Our ears do the job as well. In music, we can identify a guitar as a guitar throughout a song, even when its timbre, pitch, loudness, or environment change. In speech perception, vowels and consonants are perceived as constant even if they sound very different due to the speaker’s age, sex, or dialect. For example, the word “apple” sounds very different when a two year-old boy and a 30 year-old woman say it, because their voices are at different frequencies and their mouths form the word differently… but we perceive the sounds to be the same. This is thanks to auditory perceptual constancy!