05: sensory; Attentional and Perceptual Processes / Introduction to Psychology (2023)

After reading this chapter you will be able to do this

The quality of life is determinedfor their activities.

– Aristotle

introduction

know the world

The world we live in is filled with a wide variety of objects, people and events. Look at the room you are sitting in. You will find so many things. To name a few, you can see your table, chair, books, bag, clock, pictures on the wall, and many other things. Their sizes, shapes and colors are also different. As you move to other rooms in your house, you will notice other new things (e.g. pots and pans, Almirah, TV). If you go beyond your house, you will find many more things that you normally know (trees, animals, buildings). These types of experiences are very common in our daily lives. We hardly have to make an effort to get to know them.

If someone asks you, "How do you know that these various things exist in your room, in your house, or in the outside environment?" you will most likely answer that you see or experience them all around you. You are trying to convey to the person that knowledge about various objects is possible with the help of our sensory organs (e.g. eyes, ears). These organs collect information not only from the outside world, but also from our own body. The information gathered by our sense organs forms the basis of all our knowledge. The sense organs capture different types of information about different objects. However, in order to be registered, objects and their properties (e.g. size, shape, color) must be able to attract our attention. The recorded information must also be sent to the brain, which constructs meaning from it. Thus, our knowledge of the world around us depends on three basic processes called sensation, attention, and perception. These processes are strongly linked; Therefore, they are often viewed as different elements of the same process called cognition.

Nature and Types of Stimulus

The external environment that surrounds us contains a variety of stimuli. Some of them can be seen (eg a house), others can only be heard (eg music). There are several others that we can smell (e.g. the scent of a flower) or taste (e.g. candy). There are others that we can experience through touch (for example, the softness of a cloth). All of these stimuli provide us with different types of information. We have highly specialized sensory organs to deal with these different stimuli. As humans, we are given seven sense organs. These sense organs are also known as sensory receptors or information gathering systems because they receive or collect information from a variety of sources. Five of these sense organs collect information from the outside world. These are eyes, ears, nose, tongue and skin. While our eyes are primarily responsible for seeing, the ears for hearing, the nose for smelling and the tongue for tasting, the skin is responsible for experiencing touch, heat, cold and pain. Our skin has specialized receptors for heat, cold and pain. In addition to these five external sense organs, we also have two deep senses. They are called the kinesthetic and vestibular systems. They provide us with important information about the position of our body and the movement of related body parts. With these seven sense organs we register ten different types of stimuli. For example, you can tell if a light is bright or dim, if it's yellow, red or green, etc. With sound, you can tell if it's loud or soft, melodious or distracting, etc. These different stimulus qualities are also registered by our sense organs .

sensory modalities

Our sense organs provide us with first-hand information about our outer or inner world. The initial experience of a stimulus or an object registered by a specific sense organ is called sensation. It is a process by which we recognize and encode a variety of bodily stimuli. Sensation also refers to the immediate basic experiences of stimulus attributes such as "hard", "warm", "loud" and "blue" resulting from a corresponding stimulation of a sensory organ. Different sensory organs process different forms of stimuli and serve different purposes. Each sense organ is highly specialized to deal with a specific type of sense organinformationTherefore, each of them is called a sense modality.

Functional limitations of the sense organs

Before moving on to a discussion of the sense organs, it is important to note that our sense organs function with certain limitations. For example, our eyes cannot see things that are too dark or too bright. Likewise, our ears can hear neither very quiet nor very loud noises. The same applies to other sense organs. As humans, we function within a limited range of stimulation. In order to be perceived by a sensory receptor, a stimulus must be of optimal intensity or magnitude. The relationship between stimuli and the sensations they evoke has been studied in a discipline calledPsychophysik.

To be noticed, a stimulus must have a minimum value or weight. The minimum value of a stimulus required to activate a particular sensory system is referred to asabsolute thresholdÖabsolute lemon(ALABAMA). For example, if you add a grain of sugar to a glass of water, you may not find any sweetness in that water. Adding a second pellet to the water may not taste sweet either. But if you keep adding grains of sugar, one at a time, there comes a point when you say the water is sweet now. The minimum number of grains of sugar needed to say the water is sweet is the AL of sweetness.

At this point it should be noted that the AL is not a fixed point; Instead, it varies significantly between individuals and situations, depending on people's organic conditions and their motivational states. So we have to rate it based on a series of trials. The number of grains of sugar that can evoke the experience of "sweetness" in water 50 percent of the time is referred to as the NA for sweetness. If you add a larger amount of granulated sugar, there is a higher chance that the water will be sweeter than normal.

Since it is not possible for us to perceive all stimuli, it is also not possible to distinguish all stimuli. In order to perceive two stimuli as different from each other, there must be a minimal difference.Difference between the value of these charms. the smallestThe difference in value of two stimuli necessary for them to be perceived as different is calleddifference thresholdÖlemon difference(DL). To understand this, we can continue with our "sugar water" experiment. As we have seen, pure water feels sweet after adding a few grains of sugar. Let's remember this cutie. The next question is: How many grains of sugar does it take in water to experience its different sweetness than before? Add granulated sugar one at a time, testing the water each time. After adding a few pellets you will immediately notice that the water is now sweeter than before. The number of grains of sugar added to the water to create a sweetness experience that is 50 percent different from the previous sweetness is called the DL of sweetness. Therefore, the difference threshold is the minimal change in a physical stimulus capable of producing a difference in sensation 50 percent of the time.

You may now realize that understanding sensation is not possible without understanding the AL and DL of different types of stimuli (e.g. visual, auditory), but that is not enough. Sensory processes do not only depend on the properties of the stimulus. The sensory organs and the nerve pathways that connect them to various centers in the brain also play a crucial role in this process. A sensory organ picks up the stimulus and encodes it as an electrical impulse. In order to be perceived, this electrical impulse must reach the higher brain centers. Any structural or functional defect or damage to the recipient organ, its nerve pathways, or the affected area of ​​the brain can result in partial or total loss of sensation.

visual Sensation

Of all the sensory modalities, vision is the most developed in humans. Various estimates show that we use it in about 80 percent of our transactions with the outside world. Hearing and other senses also play a key role in gathering information from the outside world. We will discuss seeing and hearing in detail. The main features of other senses are shown in Table 5.1.

Visual sensation begins when light enters the eyes and stimulates our visual receptors. Our eyes are sensitive to a spectrum of light whose wavelength ranges from 380 nm to 780 nm (nm refers to a nanometer, which is one billionth of a meter). No sensation is registered outside this range of light.

the human eye

A diagram of the human eye is shown in Figure 5.1. As you can see, our eye consists of three layers. There is a transparent one on the outer layercorneaand a hardscleroticsurrounding the rest of the eye. Protects the eye and keeps its shape. The middle layer is calledchoroid, which is richly supplied with blood vessels. The inner layer is known asRetina. It contains the photoreceptors (rods and cones) and an elaborate network of interconnected neurons.

The eye is generally compared to a camera. For example, the eye and the camera have a lens. HeSpringdivides the eye into two unequal chambers, viz.aqueous chamberjvitreous chamber. The aqueous humor is located between the cornea and the lens. It's smaller and filled with a water-like substance calledaqueous humor. The vitreous humor is located between the lens and the retina. It's filled with a gelatinous protein, calledvitreous. These liquids help keep the lens in place and in the right shape. They also allow enough flexibility for accommodation, a process by which the lens changes shape to focus on objects at different distances. This process is regulated byZiliary musclesattached to the lens. These muscles flatten the lens to focus on distant objects and thicken it to focus on close objects. Like a camera, the eye also has a control mechanismthe amount of incident light. HeIrisserves this purposeHE. It's a disc-shaped colored membrane that lies between the cornea and the lens. It controls the amount of light entering the eye by regulating the dilation of the pupil. In dim light, the pupil dilates; in bright light it contracts.

Retinait is the innermost layer of an eye. It consists of five types of light-sensitive cells, among which rods and cones stand out.The rodThey are the receptors for scotopic vision (night vision). They work at low light intensities and lead to achromatic (colorless) vision.conesThey are the receptors for photopic (daylight) vision. They work in high light levels and readd to chromatic (color)Vision. Each eye contains about 100 million rods and about 7 million cones. The cones are highly concentrated in the central region of the retina that surrounds themFovea, which is a small circular region the size of a pea. It is also known asyellow spot. It is the area of ​​maximum visual acuity. In addition to the photoreceptors, the retina also contains a bundle of axons from a cell (called a ganglion cell) that carries theoptic nerve, which leads to the brain.

eye work

Adjustment

The human eye can function in a very wide range of light intensities. Sometimes we have to undergo a rapid change in illuminance. For example, when we watch a morning movie, it is difficult for us to see things in the room when we enter it. However, after spending about 15-20 minutes there, we can see everything. When we go outside after the show, we find the light outside the hall too bright to see things or even keep our eyes open at times. However, in about a minute we feel comfortable and can see things properly. This adaptation occurs faster than when entering the room. The process of adjusting to different light intensities is called “visual adjustment”.

easy adjustmentrefers to the process of adjusting to bright light after exposure to dim light. This process takes almost a minute or two. On the other hand,dark adaptationrefers to the process of adjusting to a dimly lit environment after exposure to bright light. This can take half an hour or longer, depending on the previous exposure to light. There are certain ways in which these processes can be facilitated. Here's an interesting activity to demonstrate this process for you.

Photochemical basis of adaptation to light and dark: You may be wondering why light and dark adaptations take place. According to the classical view, adaptations to light and dark take place as a result of certain photochemical processes. The rods have a light-sensitive chemical calledRhodopsinor visual purple. Exposure to light bleaches or decomposes the molecules of this chemical substance. Under such conditions, the eyes adapt to light. On the other hand, dark adaptation is achieved by removing light and thus allowing restorative processes to regenerate pigments in the rods with the help of vitamin A. The regeneration of rhodopsin in the chopsticks is a time-consuming process. Therefore, dark adaptation is a slower process than light adaptation. It has been found that people with vitamin A deficiency do not adjust to the dark at all and find it very difficult to move around in the dark. This condition is commonly known as night blindness. A parallel chemical thought found in cones is known asyodopsina.

color vision

In our interaction with the environment, we not only experience a variety of objects, but also their colors. It should be noted that color is a psychological property of our sensory experience. It arises when our brain interprets the information it receives from the outside world. It should be remembered that light is physically described in terms of wavelength, not color. As we haveAs read above, the visible spectrum is a range of energies (380-780nm) that our photoreceptors can detect. Energy lower or higher than the visible spectrum is harmful to the eyes. Sunlight is a perfect blend of seven colors like a rainbow. The observed colors are violet, indigo, blue, green, yellow, orange and red, abbreviated as "VIBGYOR".

The dimensions of the paint

A person with normal color vision can distinguish more than seven million different shades of color. Our color experiences can be described in terms of three basic dimensions known as hue, saturation, and lightness.hueis a property of bright colors. In simple terms, it refers to the name of the color, e.g.., red, blue and green. Hue varies with wavelength, and each color is identified with a specific wavelength. For example, blue has a wavelength of around 465 nm and green around 500 nm. Achromatic colors such as black, white or gray are not characterized by shading.saturationIt is a psychological attribute that refers to the relative amount of hue of a surface or object. Light of a single wavelength (monochromatic) appears highly saturated. When we mix different wavelengths, the saturation decreases. The gray color is fully unsaturated.Glowis the perceived light intensity. Varies between chromatic and achromatic colors. White and black represent the top and bottom of the lightness dimension. White has the highest gloss level while black has the lowest level.

mixture of colorses

There is an interesting relationship between colors. They form complementary pairs. Mixed in the right ratio, complementary colors result in an achromatic gray or white. Examples of complementary colors are red-green and yellow-blue. Red, green and blue are namedprimary colors, because by mixing the light of these three colors can create almost any color. The most famous example is the television screen. It contains blue, red and green spots. Combinations of these three create different colors and tones that we see on the television screen.

according to pictures

This is quite an interesting phenomenon related to visual sensations. The effect of a visual stimulus persists for some time, even after that stimulus has been removed from the visual field. This effect is named after the image. Afterimages are positive and negative.Positive afterimagesbe similar to the original stimulus in terms of hue, saturation and lightness. They usually appear after brief, intensive stimulation of the dark-adapted eyes. On the other hand,Negative after picturesThey appear in complementary colors. These images appear when a person gazes at a patch of a specific color for at least 30 seconds and then shifts the gaze to a neutral background (such as a white or gray surface). When the subject looks at the color blue, the negative afterimage appears yellow. Similarly, a red stimulus produces a green negative afterimage.

auditory sensation

Hearing or hearing is also an important sensory modality that is of great value to us. It provides us with reliable spatial information. In addition to orientation towards specific objects or people, it also plays an important role in spoken communication. The auditory sensation begins when sound enters our bodyear and stimulates the most important hearing organs.

The human beingOhr

The ear is the main receptor for auditory stimuli. Although its well-known function is hearing, it also helps us maintain body balance. The structure of an ear is divided into three segments called the outer ear, middle ear and inner ear (Fig. 5.2).

outer ear: Contains two main structures, viz.Ohrmuscheljear canal. The pinna is a funnel-shaped cartilage structure that picks up sound waves from the environment. The ear canal is a hair and wax-protected canal that carries sound waves from the pinna to the ear.eardrumÖeardrum.

middle ear: The middle ear starts witheardrum, a thin membrane that is very sensitive to sound vibrations. This is followed by thePaukenhöhle. It is connected to the pharynx with the help ofear trumpet, which maintains air pressure in the tympanic cavity. From the cavity, the vibrations go to three auditory ossicles known asMaleo(Hammer),Anvil(anvil) andstirrup(Stirrup). They increase the intensity of sound vibrations by about 10 times and send them to the inner ear.

inner ear: The inner ear has a complicated structure known ashäutiges Labyrinth, which is encapsulated in a bony shell calledbony labyrinth. There is a lymph-like fluid in the space between thema bony labyrinth and a membranous labyrinth. Is calledPerilymphe.

The bony labyrinth has threesemicircular canalsperpendicular to each other a cavity, calledlobby, and a convoluted structure, calledSnail. The semicircular canals have fine hair cells that are very sensitive to changes in posture and body orientation. Inside the bony cochlea is a membranous cochlea, also known as the cochleamedium scale. It is filled with endolymph and has a spirally wound membrane, calledBasilarmembran. It has fine hair cells arranged in series to form theCorti-Organ. This is the main organ for hearing.

ear work

Pavilion collects sound vibrations and sends them through the ear canal to the eardrum. From the tympanic cavity, the vibrations are transmitted to the three ossicles, which increase their strength and transmit them to the inner ear. in tThe inner ear, the cochlea, receives sound waves. The vibrations set the endolymph in motion, which also causes the organ of Corti to vibrate. Finally, the impulses are sent to the auditory nerve, which exits at the basecochlea and reaches the auditory cortex where the impulse is interpreted.

Ton as Reis

We all know that sound is a stimulus to the ears. It is the result of pressure fluctuations in the external environment. Any physical movement disturbs the surrounding medium (i.e. the air) and pushes the air molecules back and forth. This results in pressure changes propagating outward in the form of sound waves at a velocity of about 1100 ft/sec. These changes propagate in ripples, much like the ripples produced by a stone thrown into a pond. When these sound waves hit our ears, they trigger a series of mechanical pressure changes that ultimately activate the auditory receptors.

The simplest type of sound wave is one that causes successive changes in pressure over time in the form of a single repeating sine wave (Fig. 5.3). Sound waves vary in both amplitude and wavelength.Amplitudeis a general measure of the magnitude of the stimulus. It is the amount of pressure change, ie the degree of displacement of the molecules from the resting position. In Figure 5.3, the amplitude of the sound wave is represented as the distance of the peak or valley from its center position.wavelengthis the distance between the two peaks. Sound waves are basically created by the alternating compression and decompression (dilution) of air molecules. A complete change in pressure from compression to rarefaction and back to compression cycles the wave.

Volumeof the sound is determined by its amplitude. High amplitude sound waves are perceived as strong; those with small amplitude are perceived as smooth. Volume is measured in decibels (db).Pasorefers to the pitch or gravity of a sound. The seven tones used in Indian classical music represent a gradual increase in pitch. Frequency determines the pitch of a sound wave. The higher the frequency, the higher the pitch. The audible range is generally 20 Hz to 20,000 Hz.Timbrerefers to the type or quality of a sound. For example, the sound of a car engine and the sound of a person speaking differ in quality or timbre. The timbre of a sound reflects the complexity of its sound waves. Most sounds in natural environments are complex.

attention processes

In the previous section, we discussed some sensory modalities that help us gather information from the outside world as well as from our internal system. Many stimuli hit our sense organs at the same time, but we do not perceive them all at the same time. Few of them are noticed. For example, when you enter your classroom, you will find different things in it like doors, walls, windows, paintings on the walls, tables, chairs, students, school bags, water bottles, etc., but you selectively focus on only one or two of them at a time.The process of selecting particular stimuli from a group of others is commonly referred to as attention.

At this point it should be noted that besides selection, attention also refers to some other characteristics such as alertness, concentration and searching. Alertness refers to a person's willingness to cope with stimuli that are presented to them. While participating in a race at your school, you may have seen the participants at the starting line in a state of alert, waiting for the starting whistle to sound. Concentration refers to focusing awareness on certain specific objects while excluding others for the time being. For example, in the classroom, a student is concentrating on the teacher's reading and ignoring all sorts of noises coming from different corners of the school. When searching, an observer is looking for a specific subset of objects in a set of objects. For example, when you pick up your little sister and brother from school, just look for them among countless boys and girls. All these activities require a certain effort on the part of people. Attention in this sense refers to the "allocation of effort".

Attention has both a focus and an edge. When the field of consciousness is focused on a specific object or event, it is called the focus or focal point of attention. Conversely, when objects or events are far from the center of consciousness and one is only dimly aware of them, they are said to be unconscious.

Attention has been classified in a number of ways. A process-oriented view divides it into two types viz.selectivejconsistent. We will briefly dwell on the main features of this type of care. Sometimes we can take care of two different things at the same time. When this happens, it is invokeddivided attention. Box 5.2 describes when and how attention sharing is possible.

selective attention

Selective attention is primarily concerned with choosing a limited number of stimuli or objects from a large number of stimuli. We have already pointed out that our perceptual system has a limited capacity to take in and process information. This means that you can only deal with a few stimuli at a time. The question is which of these stimuli are selected and processed? Psychologists have identified a number of factors that determine stimulus selection.

Factors affecting selective attention

Several factors influence selective attention. These generally relate to the properties of the stimuli and the properties of the individuals. They are generally divided into "external" and "internal" factors.

External FactorsThey relate to the properties of the stimuli. Other things remain constant, the size, intensity and movement of stimuli seem to be important determinants of attention. Large, bright, moving stimuli easily attract our attention. Stimuli that are novel and moderately complex also easily come into focus. Studies show that human photographs are more likely to attract attention than photographs of inanimate objects. Likewise, rhythmic auditory stimuli are more easily heeded than verbal narratives. Sudden and intense stimuli have a wonderful ability to attract attention.

internal The factorthey are in the individual. These can be divided into two main categories viz. Motivational factors and cognitive factors.motivating factorsthey relate to our biological or social needs. When we are hungry, we even detect a faint smell of food. A student taking a test is likely to focus more on a teacher's directions than other students.cognitive factorsThey include factors such as interest, attitude and preparation set. Objects or events that appear interesting can easily be perceived by individuals. Similarly, we are quick to pay attention to certain objects or events that we are well disposed toward. The preparation set creates a mental state to act in a certain way and the individual's disposition to respond to one type of stimuli and not others.

theories of selective attention

Several theories have been developed to explain the process of selective attention. We will briefly discuss three of these theories.

FiltertheorieIt was developed by Broadbent (1956). According to this theory, many stimuli enter our receptors at the same time, creating a kind of “bottleneck” situation. As they move through the short-term memory system, they enter the selective filter, which allows only a stimulus to pass through to higher levels of processing. At that moment, other stimuli intrude. Therefore, we only perceive the stimulus accessed through the selective filter.

Theory of filter dampingit was developed by Triesman (1962) by modifying Broadbent's theory. This theory proposes that stimuli that do not access the selective filter at a given point in time are not completely blocked. The filter only dampens (weakens) its strength. Therefore, some stimuli manage to escape through the selective filter to reach higher levels of processing. It is pointed out that personally relevant stimuli (e.g. one's own name at a group meal) can also be perceived at a very low noise level. Such stimuli, although rather weak, mThey can also generate a reaction from time to time by swiping through the selective filter.

Multimode-TheorieIt was developed by Johnston and Heinz (1978). This theory posits that attention is a flexible system that allows three levels of selection of one stimulus over others. In stage one, sensory representations (eg, visual images) of the stimuli are constructed; in stage two, the semantic representations (e.g. names of objects) are constructed; and in stage three, sensory and semantic representations come into consciousness. It is also noted that more processing requires more mental effort. When messages are selected based on level one (early selection) processing, less mental effort is required than when the selection is based on level three (late selection) processing.

sustained attention

While selective attention is primarily concerned with choosing stimuli, sustained attention is concerned with concentration. It relates to our ability to sustainfocus attention on an object or event for longer. It is also known as "monitoring". Sometimes people need to focus on a specific task for many hours. Air traffic controllers and radar readers give us good examples of this phenomenon. You must constantly observe and monitor the signals on the screens. The appearance of signals in such situations is often unpredictable and errors in signal detection can be fatal. Therefore, a lot of vigilance is required in such situations.

Factors affecting sustained attention

Several factors can facilitate or inhibit an individual's performance on tasks requiring sustained attention.sensory modalityIt's one of them. It has been found that performance is higher when the stimuli (called cues) are auditory than when they are visual.Clarity of stimuliis another factor.Intense and long-lasting stimuli promote sustained attention and lead to better performance.temporal uncertaintyis a third factor. When stimuli appear at regular intervals, they are better served than when they appear at irregular intervals.spatial uncertaintyis a fourth factor. Stimuli that appear in a fixed place are easy to notice, while those that appear in random places are difficult to notice.

Attention has several practical implications. The number of objects that can be looked at at a glance is used to design the number plates of motorcycles and cars so that they can be easily recognized by traffic police in the event of traffic violations (Table 5.3). A number of children do not do well in school simply because of the attention problem. Box 5.4 contains some interesting informationAabout an attention deficit disorder.

perceptual processes

In the previous section, we examined how stimulation of the sense organs leads us to perceive something like a flash of light, a sound, or an odor. This elementary experience called sensation gives us no understanding of the stimulus that stimulated the sense organ. For example, it doesn't tell us anything about the source of the light, sound, or scent. In order to understand the raw material provided by the sensors, we process it further. We make sense of stimuli using our learning, memory, motivation, emotions, and other psychological processes.The process by which we recognize, interpret, or make sense of the information that the sense organs give us is called cognition.When interpreting stimuli or events, individuals often construct them in their own way. Therefore, perception is not simply an interpretation of objects or events in the external or internal world as they exist, but also a construction of those objects and events from one's point of view.

The process of meaning-making involves certain threads. These are shown in Fig. 5.4.

Fig.5.4: Partial processes of perception

Processing approaches in perception

How do we identify an object? Do we identify a dog because we first recognized its furry coat, four legs, eyes, ears, etc., or do we recognize these different parts because we first identified a dog? The idea that the recognition process starts from the parts that serve as the basis for recognizing the whole is calledProcessing from bottom to top. The notion that the recognition process starts from the whole and leads to the identification of its various components is known asProcessing from top to bottom. The bottom-up approach emphasizes the properties of the stimuli in perception and views perception as a mental construction process. The top-down approach places the focus on the perceiver and views perception as a process of recognizing or identifying stimuli. Studies show that in cognition, both processes interact to give us an understanding of the world.

the perceiver

Humans are not just mechanical and passive recipients of stimuli from the outside world. They are creative beings and try to understand the outside world in their own way. In this process, your motivations and expectations, cultural knowledge, past experiences and memories, as well as values, beliefs, and attitudes play an important role in making sense of the outside world. Some of these factors are described here.

Motivation

The needs and desires of a perceiver strongly influence their perception. People want to satisfy their needs and desires in different ways. One way to do this is to perceive the objects in an image as something that satisfies your needs. Experiments have been conducted to examine the influence of hunger on cognition. When shown ambiguous images, hungry people were found to perceive them as images of food objects more often than full (non-hungry) people.

expectations or sets of perceptions

Expectations about what we might perceive in a certain situation also influence our perception. This phenomenon of perceptual familiarity or perceptual generalization reflects a strong tendency to see what we expect to see, even when the results do not accurately reflect external reality. For example, if your milkman delivers your milk at around 5:30 am every day, any knock on the door at that time is likely to be perceived as the milkman's presence, even if it is someone else.

Kognitive Stile

Cognitive style describes a consistent approach to our environment. It significantly influences the way we perceive the environment. There are different cognitive styles with which people perceive their environment. One of the most commonly used in studies is the “field-dependent and independent” cognitive style. Field-dependent people perceive the outside world in its entirety, i.e. globally or holistically. On the other hand, field-independent people perceive the outside world by dividing it into smaller units, that is, in an analytical or differentiated way.

Look at Figure 5.5. Can you find the hidden triangle in the picture? How long does it take to find it? Try to find out how long it takes other students in your class to find the triangle. Those who can do it quickly are called "Field Independents"; those that last long are referred to as "field dependents."

Cultural background and experiences

The different experiences and learning opportunities available to people in different cultures also influence their perception. people comeng from a non-image environment does not recognize objects in images. Hudson examined the perception of images by African subjects and identified several difficulties. Many of them could not identify the objects depicted (e.g. antelopes, spears). They also could not perceive the distance in the images and misinterpreted the images. It has been found that Eskimos make a fine distinction between a variety of snow that we may not be able to notice. It has been discovered that some aboriginal groups in the Siberian region distinguish between dozens of reindeer skin colors, which would not be possible for us.

These studies indicate that the perceiver plays a key role in the perception process. People process and interpret stimuli in their own way, depending on their personal, social, and cultural circumstances. These factors not only fine-tune our perception, but also change it.

Principles of perceptual organization

Our visual field is a collection of different onesnt elements such as points, lines and colors. However, we perceive these elements as organized wholes or complete objects. For example, we see a bicycle as a whole object, not as a collection of different parts (e.g. seat, wheel, handle). The process of organizing the visual field into meaningful wholes is known asshape perception.

You may be wondering how the different parts of an object are organized into a meaningful whole. You can also ask if there are specific factors that facilitate or inhibit this organizing process.

Various scholars have attempted to answer such questions, but the most accepted answer was given by a group of researchers calledgestalt psychologists. Special mention should be made of Koehler, KoffKa and Wertheimer. Shape means a regular figure or shape. According to gestalt psychologists, we perceive different stimuli not as discrete elements, but as an organized "whole" that has a specific shape. They believe that an object's form resides in its whole, which is distinct from the sum of its parts. For example, a pot with a bouquet of flowers is a whole. When the flowers are removed, the pot remains a whole. It's the configuration of the pot that has changed. The flower pot is a configuration; no flowers is another setup.

Gestalt psychologists also point out that our brain processes are always geared towards the perception of agood figureÖpragnanz. This is why we perceive everything to be organized. The most primitive organization takes the form offigure-floor separation. When we look at a surface, certain aspects of the surface stand out clearly as separate entities while others do not. For example, when we see words on a page or a painting on a wall, or birds flying in the sky, the words, painting, and birds stand out against the background and are perceived as figures, while the page, wall, etc. is the sky behind the figure and is perceived as the background.

To prove this experience, see Fig. 5.6 below. You see the white part of the figure that looks like a vase (pot) or the black part of the figure that looks like two faces.

We distinguish the figure from the background by the following features:

1. The figure has a definite shape while the background is relatively shapeless.

2. The character is more organized compared to its background.

3. The figure has a clear border (outline) while the background has no border.

4. The character protrudes from the background while the background is behind the character.

5. The figure appears clearer, limited, and relatively closer, while the background appears relatively unclear, boundless, and far away from us.

The discussion presented above shows that people perceive the world in organized wholes rather than in separate parts. Gestalt psychologists have given us various laws to explain how and why various stimuli in our visual field are organized into meaningful whole objects. Let's look at some of these principles.

The principle of proximity

Objects that are close together spatially or temporally are perceived as belonging together or as a group. For example, Figure 5.7 doesn't look like a square dot pattern, but rather a series of rows of dots. Similarly, Figure 5.7 looks like a group of points in rows together.

Fig.5.7: Proximity

The similarity principle

Objects that are similar to each other and have similar properties are perceived as a group. In Fig.5.8, the small circles and squares are equally spaced both horizontally and vertically, so proximity does not come into play. Instead, we see alternating columns of circles and squares.

Fig.5.8: Similarity

The principle of continuity

This principle states that we tend to perceive objects as belonging together when they appear to form a continuous pattern. For example, we are more likely to identify two linesa-bjCDIntersection, identified as four lines meeting in the middlePage.

Fig.5.9: Continuity

The principle of symmetry

This principle suggests that symmetrical areas tend to look like figures against asymmetrical backgrounds. For example, in Fig.5.11 the black areas look like figures (since they have symmetrical properties) against their asymmetrical white background.

Perception of space, depth and distance

The field of view, or the surface in which things can exist, move, or be placed, is called space. The space we live in is organized in three dimensions. We perceive not only the spatial properties (e.g. size, shape, direction) of different objects, but also the distance between the objects that are in this space. Although the images of objects projected onto our retinas are flat and two-dimensional (left, right, top, bottom), we still perceive three dimensions in space. Why is it so? It arises from our ability to translate two-dimensional retinal vision into three-dimensional perception. The process of seeing the world in three dimensions is called distance or depth perception.

Depth perception is important in our daily lives. For example, when we drive we use depth to estimate the distance to an oncoming car, or when we decide to call someone walking down the street we use depth to determine the volume at which we call.

When perceiving depth, we rely on two main sources of information called cues. One is called binocular references because they require both eyes. Another is called monocular cues because they allow us to perceive depth with just one eye. Several of these signals are used to transform a two-dimensional image into a three-dimensional perception.

Monocular Clues (Psychological Clues)

Monocular depth perception cues are effective when viewing objects with only one eye. Artists often use these cues to add depth to two-dimensional paintings. Therefore they are also referred to as image signals. Some important monocular cues that help us judge distance and depth on two-dimensional surfaces are described below. You can find some of them in Fig.5.14.

relative size: The size of the retinal image allows us to judge distance based on our past and present experiences with similar objects. As objects get farther away, the retinal image gets smaller and smaller. We tend to perceive an object further away when it appears small and closer when it appears larger.

interposition or overlay: These signals occur when part of the object is covered by another object. The overlapping object is seen further away while the overlapping object appears closer.

Straight line perspective: This reflects a phenomenon where distant objects appear closer together than closer objects. For example, parallel lines like railroad tracks appear to converge with a vanishing point on the horizon as distance increases. The more the lines converge, the further apart they appear.

Aerial Perspektive: The air contains microscopic particles of dust and moisture that make distant objects appear blurry or blurry. This effect is called aerial perspective. For example, distant mountains appear blue due to the scattering of blue light in the atmosphere, while the same mountains appear closer when the atmosphere is clear.

light and shadow: to illuminate some parts of tThe object is highlighted while some parts are darkened. Light and shadow tell us how far away an object is.

relative height: Larger objects are perceived as closer to the viewer and smaller objects as further away. If we expect two objects to be the same size and they are not, the larger of the two will appear closer and the smaller will appear farther away.

texture gradient: It represents a phenomenon by which the field of view, which has a higher element density, is seen further. In Fig.5.15, the density of the stones increases with distance.

Fig.5.15: Gradient texture

motion parallax: It is a kinetic monocular signal and is therefore not considered an image signal. It occurs when objects at different distances are moving at different relative speeds. Distant objects appear to move slower than close objects. The speed of an object's movement tells you its distance. For example, when we ride on a bus, objects that are closer move “against” the direction of the bus, while objects that are further away move “with” the direction of the bus.

Binocular signals (physiological signals)

Both eyes provide some important clues to depth perception in three-dimensional space. Three of them were particularly interesting.

Retinal or binocular disparity: Retinal differences occur because the two eyes have different positions in our heads. They are about 6.5 centimeters apart horizontally. Because of this distance, the image that forms on the retina of each eye of the same object is slightly different. This difference between the two images is called retinal disparity. The brain interprets a large retinal disparity as a close object and a small retinal disparity as a distant object, since the disparity is smaller for distant objects and larger for close objects.

convergence: When we see a close object, our eyes converge inward to deliver the image to the fovea of ​​each eye. A muscle group sends messages to the brain about how much the eyes are turning inward, and these messages are interpreted as signals for depth perception. The degree of convergence decreases as the object moves away from the observer. You can experience convergence by putting a finger in front of your nose and slowly moving it closer. The more the eyes turn inward or converge, the closer the object appears in space.

Accommodation:Accommodation is a process in which we use the ciliary muscle to focus the image on the retina. These muscles change the thickness of the lens of the eye. When the object moves away (more than 2 meters), the muscle relaxes. As the object gets closer, the muscle contracts and the lens thickens. The signal about the degree of contraction of the muscle is sent to the brain, which indicates the distance.

perceptual constancy

The sensory information we receive from our surroundings is constantly changing as we move. However, we form a stable perception of an object that we see from any position and with any light intensity. Perception of objects as relatively stable despite changes in stimulation of sensory receptors is referred to as perceptual constancy. Here we will examine three types of perceptual constancy that we commonly experience in our visual realm.

constancy of size

The size of an image on our retina changes with the distance of the object from the eye. The further away, the smaller the image. On the other hand, our experience shows that, within certain limits, the object appears approximately the same size regardless of its distance. For example, if you approach your friend from a distance, your perception of the friend's size does not change much, even though the retinal image (image on the retina) increases. This tendency for the perceived size of objects to remain relatively unchanged with changes in their distance from the viewer and the size of the retinal image is called size constancy.

form constancy

In our perception, the shapes of familiar objects remain unchanged, even though the retinal image pattern changes due to differences in their orientation. For example, a dinner plate has the same shape as the picture on itprojects on the retina a circle or an ellipse, or roughly a short line (when the plate is viewed from the edge). It is also referred to as shape constancy.

gloss consistency

Not only do visual objects appear constant in shape and size, but they also appear constant in their degree of whiteness, grayness, or blackness, even though the amount of physical energy they reflect varies significantly. In other words, our perception of brightness does not change even though the amount of reflected light reaching our eyes changes. The tendency to keep the apparent brightness constant at different illuminance levels is called brightness constancy. For example, the surface of a paper that appears white in sunlight is also perceived as white in room light. Similarly, charcoal that looks black in the sun also looks black in room light.

delusions

Our perceptions are not alwaysit's true Sometimes we fail to interpret sensory information correctly. This leads to a mismatch between physical stimuli and their perception. These misperceptions, which result from misinterpreting information received by our sense organs, are commonly known as illusions. We all experience these to a greater or lesser extent. They are the result of an external stimulus situation and produce the same type of experience in everyone. That is why illusions are also called "primitive organizations". Although illusions can be experienced through the stimulation of any of our senses, psychologists have studied them more often in the visual sense than in other sensory modalities.

Some perceptual illusions are universal and found in all individuals. For example, the railroad tracks seem to converge for all of us. These illusions are called universal illusions or permanent illusions because they do not change with experience or practice. another sickIdeas seem to vary from individual to individual; these are called personal illusions. In this section we will describe some important visual illusions.

geometric illusions

The Müller-Lyer illusion is shown in Figure 5.16. We all perceive line A to be shorter than line B, even though both lines are the same. This illusion is experienced even by children. There are some studies that suggest that even animals experience this illusion more or less like us. In addition to the Müller-Lyer illusion, humans experience other visual illusions (birds and animals too). In Fig.5.17 you can see the illusion of vertical and horizontal lines. Although both lines are the same, we perceive the vertical line to be longer than the horizontal line.

illusion of apparent movement

This illusion is created when a few still images are projected one after the other at a suitable speed. This illusion is known asphi phenomenon“. When we see moving images in a film screening, we are affected by this type of illusion. The succession of flickering electric lights also creates this illusion. This phenomenon can be studied experimentally using an instrument that presents two or more lights in succession. For the experience of this illusion, Wertheimer had reported that having an appropriate level of brightness, size, spatial distance, and temporal proximity of different lights was important. Without these, the points of light do not appear to move. They appear as one dot or as different dots appearing one after the other without any experience of movement.

The experience of illusions indicates that people do not always perceive the world as it is; Instead, they become involved in its construction, sometimes based on the properties of the stimuli and sometimes based on their experiences in a particular environment. This point will be further clarified in the following section.

Sociocultural influences on perception

Several psychologists hI have studied the processs of perception in different socio-cultural contexts. The questions they try to answer with these studies are: Is the organization of perception carried out uniformly by people living in different cultural contexts? Are perceptual processes universal or do they vary depending on the cultural environment? Since we know that people living in different parts of the world look different, many psychologists argue that their way of perceiving the world must be different in some way. Let's examine some studiesIt relates to the perception of illusory figures and other visual materials.

You are already familiar with Müller-Lyer and vertical-horizontal illusion figures. Psychologists have used these numbers with different groups of people living in Europe, Africa and many other places. Segall, fieldell and Herskovits conducted the most comprehensive study of illusion susceptibility, comparing samples from remote African villages and Western urban settings. It was found that African subjects showed higher susceptibility to the horizontal-vertical illusion, while Western subjects showed higher susceptibility to the Muller-Lyer illusion. Similar results have also been reported in other studies. The African subjects living in dense forests regularly experienced verticality (e.g. long trees) and developed a tendency to overestimateYou thereWesterners living in environments characterized by right angles developed a tendency to underestimate the length of lines marked by enclosing (e.g. arrowhead). This conclusion has been confirmed in several studies. It suggests that perceptual habits are learned differently in different cultural settings.

In some studies, people living in different cultural settings were given images to identify objects and interpret the depth or other events depicted on them. Hudson conducted a key study in Africa and found that people who had never seen images had great difficulty recognizing the objects depicted in them and interpreting depth cues (such as overlap). Informal home instruction and regular exposure to images were indicated as necessary to maintain the ability to perceive image depth. Sinha and Mishra have conducted several studies of image perception using a variety of images with people from different cultural backgrounds, including hunter-gatherers living in forests, farmers living in villages, and people working and living in cities. His studies indicate that the interpretation of images is strongly linked to people's cultural experiences. While people can generally recognize familiar objects in images, those less exposed to images have difficulty interpreting actions or events depicted in them.

Summary