Perception

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Perception is the mental process of interpreting the information received by the sense organs from the environment. Sensation is a physical process, whereas, perception is a psychological process. For example, upon smelling the scent of roses, a sensation is the scent receptors in the body detecting the odor of roses, but the perception may be "Mmm, this smells like roses."

Introduction

Perception is a set of psychological processes that help us understand the world around us. We encounter numerous stimuli every second through our sensory organs. It brings about awareness and interpretation of our environment. It involves selection, organization, and interpretation of the sensory information based on one's previous experiences, needs, aspirations and even considering other's experiences.

In the Western tradition perception and inference, or experience and reason, are widely recognized as the two sources of knowledge, while in India six sources (shad pramanas) are widely recognised as valid sources of knowledge.

Sensation

Sense organs are the primary sources for gathering information from the world around us and providing it to the mind for further processing. Sense organs receive the reflection emanating from the objects which are then reflected in the inner mind. A stimulus is a detectable input from the environment.

Sensory receptors are specialized neurons that respond to specific types of stimuli. When sensory information is detected by a sensory receptor, sensation has occurred. For example, light that enters the eye causes chemical changes in cells that line the back of the eye. These cells relay messages, in the form of action potentials to the central nervous system.

Sensory Organs

It is well known that the five major senses are vision, hearing (audition), smell (olfaction), taste (gustation), and touch (somatosensation). They contain sense receptors which are specialized cells unique to each sense organ and respond to specific forms of stimulation. However, a combination of sensations are generally evoked, for example, when one takes a bite into a crisp apple, one can hear the sound of crunch, get the taste of sweetness, feel the smooth skin of the fruit, see the red color of the skin and smell the aroma of apple.

Fundamental Human Senses

Sense	Perceptual Experience	Stimulus	Sense Organ	Sensation
Sight	Vision	Light waves	Eye	Colors, patterns, textures, forms
Hearing	Audition	Sound waves	Ear	Music, noise, voice, tones
Touch	Tactile	External touch	Skin	Touch, cold, warmth, pain, mechanical compression
Smell	Olfactory	Volatile substances, Aerosols (Chemical)	Nose	Odours both pleasant and unpleasant, strong and mild
Taste	Gustation	Soluble solutions, Liquids (Chemical)	Tongue	Taste of sweet, salt, bitter etc.

Somesthesis - the mechanical senses

Somesthesis refers to the mechanical senses that provide information about

• balance (the vestibular sense)
• body position and movement (proprioception and kinesthesia)
• pain (nociception)
• temperature (thermoception)

Kinesthesis is a term applied to communicating information about movement and location of body parts and receptors for these are found in joints and ligaments.

Vestibular or equilibratory sense is concerned with the sense of balance and knowledge of the body position. Receptors for this sense are in semicircular canals and vestibular sacs found in the inner ear. The vestibular organ monitors head and eye movements.

Process of Sensation

It involves three steps.

1. Reception: The process of receiving information in the form of light, heat or other physical energy by the sense organs having specialized sensory receptor cells is called reception. The minimum amount of physical energy needed to produce a sensory experience in a receptor cell is called 'absolute threshold.' For example, the tick of a watch six meters or twenty feet away can be heard under quiet conditions. A message below that threshold is said to be 'subliminal'; such a message is processed but a person is not consciously aware of it. The minimum difference that a person can detect between two stimuli 50% of the time is termed as 'just noticeable difference threshold'. Examples include the noticeable difference in the pressure on the arm, and differences in the volume of music.
2. Transduction: The conversion of received physical energy or sensory stimulus energy into electric impulse or action potential is known as transduction. The electric impulses are the 'readable' forms of sensory information.
3. Transmission: The electric impulses travel from the source sensory organ to the brain for interpretation via the nerve fibers.

Psychophysics is a study of the relationship between the physical characteristics of stimuli and the psychological experience with them. Sensory system is used to detect events happening in our environment.

Definition of Perception

An awareness about the external stimuli gathered by the sense-organs is the result of a higher mental process called 'perception'. An immediate interpretation of a sense impression is called a perception. It helps us interpret the world around us and in making an appropriate decision in simple and complex situations and stimuli. Perception is a process of selecting, organizing, and interpreting the sensory information based on previous experiences, other's experiences, needs or expectations.

Responding to a stimulus presented to one sense by perceiving a fact which could only be directly presented to another sense is exemplified also by such common expressions as that the stone ‘looks heavy,’ or that the bell 'sounds cracked.’ All this goes to show that we read meaning into the things that strike our sense organs. In other words, we perceive those things. As Woodworth states it: “We see things not as they are but as we are.”

Process of Perception

As a child sensations are not completely processed to ascribe meanings except those such as necessities say hunger. For example in an adult, a noise may arouse questions of what it may be until satisfactory answer is obtained, a meaning or significance has to be given. However, the same noise would probably startle a baby, but the sound would have no significance for him. We say the child will learn the meaning of such sound stimuli later on. This shows that a large part of human development is learning to understand the significance of the things we experience. It is only as we learn to interpret things, to read meaning into them, that we grow mentally. Broadly, the process of perception involves three steps, when a stimulus is encountered.

1. Selection

Selection is the first stage of perception. At a given time, due to various factors, the human brain consciously or unconsciously, processes only some stimuli ignoring the others. For example, when engaged in deep conversation we tune out of many sounds in the background and do not register them. The selected stimulus becomes the "attended stimulus."

Subsequent to selecting the stimulus the interpretation depends on how the information is organized for processing. Selection is influenced by some factors like attention, motivation etc.

2. Organization

It is the second stage of perception. It refers to the way sensory information is organized, interpreted, and consciously experienced. In this stage, stimuli are arranged mentally in a meaningful pattern, thus, organizing the information received. This process occurs unconsciously explained by certain principles such as those of Gestalt. Perception involves both bottom-up and top-down processing. Bottom-up processing refers to the fact that perceptions are built from sensory input. On the other hand, how we interpret those sensations is influenced by our available knowledge, our experiences, and our thoughts. This is called top-down processing.

Bottom-Up Processing	Top-down Processing
Process of perception is direct	Process of perception is indirect
Perception is a data driven process i.e., stimuli carries sufficient information to be interpreted meaningfully not relying on person's experiences.	Perception is an experience driven process i.e., stimuli does not carry sufficient information to be interpreted meaningfully thus requiring to rely on person's experiences.
J J Gibson was one of the strongest advocate of this view.	Richard Gregory was the strongest advocate of this view.

3. Interpretation

In this third stage of the process of perception, meaning is assigned to the organized stimulus. Interpretation and assigning meaning to the stimuli is based on one's own experiences, expectations, needs, beliefs, other's experiences and other factors. This stage is subjective in nature and the same stimuli can be interpreted differently by different individuals.

Factors affecting sensation and perception

Sensory Adaptation

Although our perceptions are built from sensations, not all sensations result in perception. In fact, we often don’t perceive stimuli that remain relatively constant over prolonged periods of time. This is known as sensory adaptation.

Imagine a person entering a classroom having an old analog clock. Upon first entering the room, he can hear the ticking of the clock; as he engages in conversation with classmates or listens to professor greet the class, he shall no longer be aware of the clock ticking. The clock continues to tick, and that stimulus continues to affect the sensory receptors of the person's auditory system even as time passes. The fact that he no longer perceives the sound demonstrates sensory adaptation and shows that while closely associated, sensation and perception are different. When exposed to a stimulus over a period of time there will be a diminished sensitivity to it. Constant and persistent exposure to a stimulus may make a person unresponsive to it. For example, the water in a hot tub is hot initially and after a certain period of time it no longer seems as hot. So is the case with band aid which cannot be senses after wearing it for a while.

Attention

Attention plays a significant role in determining what is sensed versus what is perceived. Imagine a party full of music, chatter, and laughter. When one is absorbed in an interesting conversation with a friend, and he/she gets tuned out all the background chatter or conversations which can be termed as noise. On interruption the person would probably be unable to answer what song was just played. Failure to notice something that is completely visible because of a lack of attention is called inattentional blindness.

Selective Attention: One of the most important functions of attention is selectivity. The selected stimulus of interest is the one on which total attention is focused, while ignoring other relevant stimuli.

Sustained Attention: Some activities involve prolonged attention such as a computer game, or gazing at the radar screen. It is the ability to attend a stimulus for a longer period of time without being distracted.

Motivation

Motivation can also affect perception. For example, while expecting a really important phone call and, taking a shower, a one thinks that one can hear the phone ringing, only to discover that it is not so. This is how a motivation or expectation to detect a meaningful stimulus can influence our perception. It can shift our ability to discriminate between a true sensory stimulus and background noise. It is common experience that when we feel hungry, our attention tends to catch the smell of food easily than when we are not hungry. Hunger is a motivation influencing our perception.

Cultural influence

The shared experiences of people within a given cultural context can have pronounced effects on perception. For example, Marshall Segall, Donald Campbell, and Melville Herskovits (1963) published the results of a multinational study in which they demonstrated that individuals from Western cultures were more prone to experience certain types of visual illusions than individuals from non-Western cultures, and vice versa.

One such illusion that Westerners were more likely to experience was the Müller-Lyer illusion. The lines appear to be different lengths, but they are actually the same length. These perceptual differences were consistent with differences in the types of environmental features experienced on a regular basis by people in a given cultural context. People in Western cultures, for example, have a perceptual context of buildings with straight lines, what Segall’s study called a carpentered world (Segall et al., 1966). In contrast, people from certain non-Western cultures with an uncarpentered view, such as the Zulu of South Africa, whose villages are made up of round huts arranged in circles, are less susceptible to this illusion (Segall et al., 1999).

Personality

Children described as thrill seekers are more likely to show taste preferences for intense sour flavors (Liem, Westerbeek, Wolterink, Kok, & de Graaf, 2004), which suggests that basic aspects of personality might affect perception. Furthermore, individuals who hold positive attitudes toward reduced-fat foods are more likely to rate foods labeled as reduced fat as tasting better than people who have less positive attitudes about these products (Aaron, Mela, & Evans, 1994).

Gestalt Principles of Perception

In the early 20th century, three German psychologists Max Wertheimer, Wolfgang Köhler and Kurt Koffka proposed new principles for explaining perception called as Gestalt principle. According to these psychologists, the process of perception does not involve perceiving an array of stimuli as an object but it involves our tendency to seek a form or pattern in it. The literal meaning of the word Gestalt is form or configuration. The basic premise of Gestalt psychology is that ‘whole is different from the sum of its part’. Based on this basic premise, Gestalt psychologists proposed a number of principles or laws to explain the process of perceptual organisation i.e., how we perceive smaller units of stimuli as a whole, having a particular pattern.

Figure-ground Relationship

According to this Gestalt principle, we tend to segment our visual world into figure and ground. Figure is the object or person that is the focus of the visual field, while ground is the background.

The other factors which determine perceptual grouping are:-

(a) Proximity: All other factors being equal, stimuli that are near one another tend to be grouped together. For example, if four stand near one another and a fifth 10 feet away, the adjacent four will be seen as a group and the distant fifth as an outsider. Events that are close in time and space are also perceived together.

(b) Similarity: Stimuli that are similar in size, shape or color tend to be grouped together.

(c) Continuity: Perception tends toward simplicity and continuity. Even if there are dots in a circular fashion, the person will see them as a complete circle.

(d) Closure: It is the tendency to complete a figure that is incomplete but has a consistent overall form. (e) Common region: Stimuli that are found within a common area tend to be seen as a group.

Illusions

Under certain circumstances, there is a tendency to misinterpret certain sensory experiences which we call as an illusion.

1. Vertical distances are perceived as greater than mathematically equal horizontal distances. A vertical line looks longer than the horizontal line upon which it is standing. A high hat will look higher than it really is on account of this illusion.
2. Filled or divided space appears greater than empty or undivided space.
3. Contrast affects our interpretation of sensations. For example, vinegar tastes very sour after eating sugar, bliss is greater if we have been despondent, a disappointment is keener if we have been keyed to a high pitch of expectancy. A famous example is the Muller-Lyer illusion of two arrows having lines facing outwards and inwards but the distance between the arrow points is the same.
4. The apparent direction of a line is influenced by the presence of other lines.
5. Illusions of area
6. Illusions of perspective

Extra Sensory Perception

Extra sensory perception is the ability to perceive objects or events in ways that cannot be explained by known sensory capacities. The study of extra sensory perception phenomena is termed as Parapsychology. Events that seem to lie outside the region of accepted scientific laws are called psi-phenomena.

An example of extrasensory perception is when a person intuitively ‘feels’ that his brother who is in another city is not well. Another example could be when you just ‘know’ that an earthquake is going to happen in your city.

Clairvoyance is the ability to perceive events or gain information in ways that appear unaffected by distance or normal barriers. Telepathy refers to the perception of another person’s thoughts or the ability to read someone else’s mind. Pre-cognition is termed as the ability to predict or perceive future events accurately. Psycho-kinesis refers to the ability to exert influence over inanimate objects by will-power (mind over matter). Very rarely we find persons are able to move objects only through concentration but without touching them. A few psychologists strongly believe in extrasensory perception but a majority does not subscribe to it.

Perception Vs Pratyaksha Pramana

In the Indian tradition, it is the self-as-knower which involves the cognitive structures and processes operating within the individual at any given time. In cognitive terms, I am the way I get to know the world.

In Indian philosophy, the terms nirvikalpa and savikalpa have been used to describe two distinct forms of perception. It is common in most schools of Indian thought to describe perception and cognition (samjñana) among babies as nirvikalpa pratyaksa, meaning that infants do not have the ability to perceive diversity or distinction, or to construe or imagine. In other words, individuals develop the ability to make meaningful distinctions, construe, and imagine (savikalpa pratyaksa), i.e., the capacity to “reason,” as they grow up.