We pay far more attention to things which fill a need or requirement. When hungry, we are far more likely to notice places to eat.
If we are not hungry, the restaurants, snack bars, and delicatessens are still there, but we do not pay attention to them as they are not meaningful to us at that time.
If we need to get somewhere in a hurry, we become very conscious of slower drivers, stoplights, or other such hindrances we might otherwise ignore. All needs have an ebb and flow to it; as need rises, attention rises, but as needs are fulfilled, attention ebbs. The same dynamic works with people.
The need for acceptance may drive us to focus more on signals affirming acceptance or signals indicating a threat to that acceptance. Early in a relationship, partners tend to be highly tuned into each other for this reason; monitoring clues indicating the status of the relationship.
If Marcus feels his relationship with Aliyah is uncertain, he will look for clues suggesting trouble or instability. His needs for acceptance and belongingness are being threatened, so his perceptions of relevant stimuli is heightened.
We pay far more attention to those things we enjoy. Scanning channels on television is a good illustration of this process. We click through numerous channels quite rapidly until something catches our interest. We pause on a channel for a moment, and if the interest continues, we quit changing channels; if not, we continue the search.
As we speak face-to-face, we tune in and out of conversations as the topics change. A conversation about a football game may not hold our interest, but a conversation about music may pull us in. A young man infatuated with a young woman will be highly attuned to any signal of interest from her, while comments from a casual friend may be ignored. Interest also allows us to perceive more detail in those things we experience.
Intense football fans will see details of play development and. The higher interest in the game leads the fan to learn more, and the more the fan learns, the more the fan can perceive.
Devoted NASCAR racing fans see strategy and technique when watching a race; non-fans see a bunch of fast cars turning left. Interest not only drives us to pay attention to the stimuli, it also encourages us to learn more about it, and so we learn to see even more detail and specifics.
A dancer who performs with the local Somali traditional music and dance group hears the nuances of the songs and sees the variety of steps in the dances; those new to this type of performance may only perceive people bouncing on the stage. This cycle applies in all facets of our lives. There are people who can discern every spice in a dish simply by tasting; there are musicians who can identify every instrument in a piece of music just by listening.
As our knowledge of effective communication rises, we will be better attuned to the dynamics occurring in a given communication situation, so we will be able to more precisely identify what is or is not working. We pay more attention to those things we believe we are supposed to experience. There are two sides to this dynamic. On one hand, if we believe we will experience something, we are more likely to focus on the stimuli fulfilling that expectation and ignore contrary input.
If Mariana's friend convinces her a certain college is a real party school, she is more likely to see confirming evidence when visiting the dorms. Years ago, one of your authors had the opportunity to take students from Minnesota to New York City.
Prior to the trip, the students talked at length about expecting to see homeless people and prostitutes. They were expecting to see something, and that is what they focused on. The danger of this dynamic, of course, is allowing expectation to override reality. Since the students expected to see the darker side of New York, they may have been blinded to the diversity and dynamic environment of the bustling city. We do not expect our friends to treat us poorly, so we are less likely to notice behaviors others might consider rude or insensitive.
The desire for affection and acceptance can often blind us to such things. A young man may not realize his girlfriend is taking advantage of him because he expects she would not treat him badly, even if his friends are trying to get him to see what is really going on. He does not expect to see evidence of her poor treatment so he, in effect, blinds himself to certain stimuli.
Physiological Limitations. Physiological limitations refer to basic sensory limitations; one or more of our senses is limited as to how well it will function.
For those who wear glasses, the world is blurred without corrective lenses; what they can sense is very limited by a physical problem. Hearing losses, diminishment of taste and smell, and loss of touch sensitivity can all cause us to have limits on what we can experience. Many who have extreme physiological limitations often compensate by using other senses in a heightened manner.
A man who is blind may attend to sounds at a much higher level than a sighted person, using those sounds as a mechanism for discerning his environment. A woman who is deaf may attend to visual cues at a much higher level than a hearing person for the same reason.
Once our senses have been stimulated, we move to the second stage of perception, organization. Organization is the process of taking the stimuli and putting it into some pattern we can recognize. As an analogy, when we come home from the grocery story with several bags, we sort those bags into the appropriate cabinets, organizing the items so their placement makes sense for later use.
How we understand this process of organization comes from Gestalt theory. In other words, how we perceive the external world is heavily determined by internal influences. Patterns are pre-existing "templates" we use to order stimuli. These are ways of organizing the stimuli that we have learned and carry with us. As children we are taught basic shapes, like "square," "triangle," and "circle," so when we experience a stimulus fitting those templates, we can make sense of what we see.
Parents teach children what it means to be "rude" or "nice," so we learn to make sense of behavior by using these learned templates. Consider Image 3. Most U. The top one fits a standard telephone number for us in the U.
The next fits the number pattern for a U. Social Security number, and the third fits the pattern for a credit card number. The last two, however, may be not be immediately apparent, yet they are commonly recognized patterns in other parts of the world. One is a Costa Rican phone number and a Scottish phone number. Of course, unless we have these templates already in place from our past experiences, we would not discern those patterns. Only because of the templates we have learned will we see these patterns, otherwise they would be just a list of random numbers.
We are always expanding our storehouse of templates. Every time we learn something new, we have created new ways of organizing stimuli. As we learn new words, each word is a new template for that set of sounds or visual shapes. Image 4 is a Mobius Strip. Often used to represent infinity, the ribbon turns so that there is no identifiable inside, outside, up, or down.
We have learned a new pattern. As discussed with sensory stimulation, the more of an interest we have in something, the more we learn about it, so that means we learn more and more patterns for that subject. Thus, when we experience something in an area of interest, we can discern more detail as we have more patterns to apply. Proximity refers to how we see one object in relation to what is around it. We do not just see a person; we see the person within their surroundings which affects our interpretation of that person.
A specific dynamic of proximity is the figure-ground relationship. The figure-ground relationship posits that as our focus on the object the figure and the background the surroundings change, interpretation changes. In applying the concept of figure-ground to people, consider professors. Seeing a professor on campus is unremarkable; we think little of it. If, however, we see them late at night coming out of a bar with a questionable reputation, our perception may be altered based on seeing them in that background.
Politicians are very aware of this dynamic, avoiding backgrounds that may cause problems. A politician does not want to be seen in a strip club but does want to be seen in church.
When the President visits Minnesota, politicians of that party may scramble to be seen with him, while politicians of the opposing party may make a point of staying away.
Seeing a young adult with a backpack on the Ridgewater College campus would undoubtedly be interpreted as "student. As we now know, we are driven to lower uncertainty and make sense of the world around us. In lowering uncertainty, we tend to favor the easiest, least confusing perception of a person or event; we like simple perceptions. First impressions are so powerful because once we have created an initial perception, it is far simpler to keep it than change it.
All stages of the perception process often happen unconsciously and in less than a second. 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.
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. 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.
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. By putting different stimuli into categories, we can better understand and react to the world around us.
Duck or Rabbit? 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?
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. Motivation has an enormous impact on the perceptions people form about the world. 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.
Emotional drives can also influence the selective attention humans pay to stimuli. Some examples of this phenomenon are:. Selective attention shows up across all ages. 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. 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. 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. 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. Below is a discussion of some of the different ways we organize stimuli. 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. 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. 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.
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 explains that our perception will complete incomplete objects, such as the lines of the IBM logo. While it is made up of just lines, we perceive the three letters.
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. 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. 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.
If we, however, film the same scene with a video camera, the whole procedure looks totally different: Now we clearly also see the fast movements; so we can directly experience the specific operation of the visual system in this respect by comparing the same scene captured by two differently working visual systems: our own, very cognitively operating, visual system and the rigidly filming video system which just catches the scene frame by frame without further processing, interpreting and tuning it.
We can utilize this phenomena for testing interesting hypotheses on the mental representation of the visual environment: if we change details of a visual display during such functional blind phases of saccadic movements, people usually do not become aware of such changes, even if very important details, e. Gregory proposed that perception shows the quality of hypothesis testing and that illusions make us clear how these hypotheses are formulated and on which data they are based Gregory, One of the key assumptions for hypothesis testing is that perception is a constructive process depending on top-down processing.
Such top-down processes can be guided through knowledge gained over the years, but perception can also be guided by pre-formed capabilities of binding and interpreting specific forms as certain Gestalts. The strong reliance of perception on top-down processing is the essential key for assuring reliable perceptual abilities in a world full of ambiguity and incompleteness. If we read a text from an old facsimile where some of the letters have vanished or bleached out over the years, where coffee stains have covered partial information and where decay processes have turned the originally white paper into a yellowish crumbly substance, we might be very successful in reading the fragments of the text, because our perceptual system interpolates and re- constructs see Figure 2.
If we know or understand the general meaning of the target text, we will even read over some passages that do not exist at all: we fill the gaps through our knowledge—we change the meaning towards what we expect.
Figure 2. A famous example which is often cited and shown in this realm is the so-called man-rat-illusion where an ambiguous sketch drawing is presented whose content is not clearly decipherable, but switches from showing a man to showing a rat—another popular example of this kind is the bistable picture where the interpretation flips from an old woman to a young woman an v. Figure 3. The young-old-woman illusion also known as the My Wife and My Mother-In-Law illusion already popular in Germany in the 19th century when having been frequently depicted on postcards.
So, we can literally say that we perceive what we know—if we have no prior knowledge of certain things we can even overlook important details in a pattern because we have no strong association with something meaningful. The intimate processing between sensory inputs and our semantic networks enables us to recognize familiar objects within a few milliseconds, even if they show the complexity of human faces Locher et al.
Top-down processes, however, are also susceptible to characteristic fallacies or illusions due to their guided, model-based nature: When we have only a brief time slot for a snapshot of a complex scene, the scene is if we have associations with the general meaning of the inspected scene at all so simplified that specific details get lost in favor of the processing and interpretation of the general meaning of the whole scene. Biederman impressively demonstrated this by exposing participants to a sketch drawing of a typical street scene where typical objects are placed in a prototypical setting, with the exception that a visible hydrant in the foreground was not positioned on the pavement besides a car but unusually directly on the car.
In this specific case, people have indeed been deceived, because they report a scene which was in accordance with their knowledge but not with the assessment of the presented scene—but for everyday actions this seems unproblematic. Although you might indeed lose the link to the fine-detailed structure of a specific entity when strongly relying on top-down processes, such an endeavor works quite brilliantly in most cases as it is a best guess estimation or approximation—it works particularly well when we are running out of resources, e.
Actually, such a mode is the standard mode in everyday life. However, even if we had the time and no other processes needed to be executed, we would not be able to adequately process the big data of the sensory input.
The whole idea of this top-down processing with schematized perception stems from F. There is clearly an enormous gap between the big data provided by the external world and our strictly limited capacity to process them. The gap widens even further when taking into account that we not only have to process the data but ultimately have to make clear sense of the core of the given situation.
The goal is to make one and only one decision based on the unambiguous interpretation of this situation in order to execute an appropriate action. This very teleological way of processing needs inhibitory capabilities for competing interpretations to strictly favor one single interpretation which enables fast action without quarrelling about alternatives.
In order to realize such a clear interpretation of a situation, we need a mental model of the external world which is very clear and without ambiguities and indeterminacies. Ideally, such a model is a kind of caricature of physical reality: If there is an object to be quickly detected, the figure-ground contrast, e. If we need to identify the borders of an object under unfavorable viewing conditions, it is helpful to enhance the transitions from one border to another, for instance. If we want to easily diagnose the ripeness of a fruit desired for eating, it is most helpful when color saturation is amplified for familiar kinds of fruits.
Our perceptual system has exactly such capabilities of intensifying, enhancing and amplifying—the result is the generation of schematic, prototypical, sketch-like perceptions and representations. Any metaphor for perception as a kind of tool which makes photos is fully misleading because perception is much more than blueprinting: it is a cognitive process aiming at reconstructing any scene at its core.
The illusion is induced by the distribution of the peripheral gray values which indeed show a continuous shift of gray levels, although in a reverse direction.
The phenomenon of simultaneous contrast helps us to make the contrast clearer; helping us to identify figure-ground relations more easily, more quickly and more securely. Figure 4. Demonstration of the simultaneous contrast, an optical illusion already described as phenomenon years ago by Johan Wolfgang von Goethe and provided in high quality and with an intense effect by McCourt : the inner horizontal bar is physically filled with the same gray value all over, nevertheless, the periphery with its continuous change of gray from darker to lighter values from left to right induce the perception of a reverse continuous change of gray values.
The first one who showed the effect in a staircase of grades of gray was probably Ewald Hering see Hering, ; pp. Teil, XII. Tafel II , who also proposed the theory of opponent color processing. Via the process of lateral inhibition, luminance changes from one bar to another are exaggerated, specifically at the edges of the bars.
This helps to differentiate between the different areas and to trigger edge-detection of the bars. Figure 5. Chevreul-Mach bands. Demonstration of contrast exaggeration by lateral inhibition: although every bar is filled with one solid level of gray, we perceive narrow bands at the edges with increased contrast which does not reflect the physical reality of solid gray bars.
This reconstructive capability is impressive and helps us to get rid of ambiguous or indeterminate percepts. However, the power of perception is even more intriguing when we look at a related phenomenon.
A very prominent example is the Kanizsa triangle Figure 6 where we clearly perceive illusory contours and related Gestalts—actually, none of them exists at all in a physical sense. The illusion is so strong that we have the feeling of being able to grasp even the whole configuration. Figure 6. Demonstration of illusory contours which create the clear perception of Gestalts. The so-called Kanizsa triangle named after Gaetano Kanizsa see Kanizsa, , a very famous example of the long tradition of such figures displayed over centuries in architecture, fashion and ornamentation.
To detect and recognize such Gestalts is very important for us. Fortunately, we are not only equipped with a cognitive mechanism helping us to perceive such Gestalts, but we also feel rewarded when having recognized them as Gestalts despite indeterminate patterns Muth et al. The detection and recognition process adds affective value to the pattern which leads to the activation of even more cognitive energy to deal with it as it now means something to us. Perceptual illusions can be seen, interpreted and used in two very different aspects: on the one hand, and this is the common property assigned to illusions, they are used to entertain people.
They are a part of our everyday culture, they can kill time. On the other hand, they are often the starting point for creating insights. And insights, especially if they are based on personal experiences through elaborative processes actively, are perfect pre-conditions to increase understanding and to improve and optimize mental models Carbon, b.
If people get really interested, they will also invest sufficient time and cognitive energy to be able to solve an illusion or to get an idea of how the illusion works. If they arrive at a higher state of insight, they will benefit from understanding what kind of perceptual mechanism is underlying the phenomenon. We can of course interpret perceptual illusions as malfunctions indicating the typical limits of our perceptual or cognitive system—this is probably the standard perspective on the whole area of illusions.
In this view, our systems are fallible, slow, malfunctioning, and imperfect.
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