UNIT 2 SENSATION AND PERCEPTION*
Structure
2.0 Learning Objectives
2.1 Introduction
2.2 Sensation
2.2.1 Human Senses and Physical Energy
2.2.2 Process of Sensation
2.3 Our Senses
2.3.1 Vision
2.3.1.1 Visual Acuity
2.3.1.2 Blind Spot
2.3.2 Hearing
2.3.3 Smell
2.3.4 Taste
2.3.5 Skin Senses
2.3.6 Kinesthetic Sense
2.4 Perception: Nature and Scope
2.5 Stages of Perception
2.6 Theoretical Approaches to Perception
2.7 Laws of Perceptual Organization: Gestalt Principles
2.8 Factors Affecting Perception
2.8.1 Effect of Motivation or Need and Set as Perceptual Determinants
2.8.2 Effect of Expectation or Perceptual Expectancy
2.8.3 Effect of Emotions
2.8.4 Effect of Stimulus Characteristic
2.8.5 Effect of Experience
2.8.6 Effect of Culture
2.9 Perception of Depth and Distance
2.9.1 Monocular Cues
2.9.1.1 Relative Size
2.9.1.2 Texture Gradient
2.9.1.3 Arial Perspective (atmospheric) or Haze
2.9.1.4 Linear Perspective
2.9.1.5 Interposition/Occlusion
2.9.1.6 Accommodation
2.9.1.7 Motion Parallax
2.9.2 Binocular Cues
2.9.2.1 Retinal Disparity (binocular parallax)
2.9.2.2 Covergence
2.10 Movement Perception
* Dr. Arti Singh, Academic Associate of Psychology, IGNOU, New Delhi and Dr. Meetu Khosla,
Associate Professor of Psychology, Daulat Ram College, Delhi University, New Delhi. [Sensation,
adapted from BPC 001, (Professor G.P Thakur, Department of Psychology, M.G. Kashi Vidyapeeth, 37
Varanasi)]
,Perception, Learning 2.11 Size Perception
and Memory
2.12 Error in Perception : Illusion
2.13 Summary
2.14 Key Words
2.15 Review Questions
2.16 References and Suggested Readings
2.17 Reference for Figure
2.18 Online Resources
2.0 LEARNING OBJECTIVES
After reading this unit, you will be able to:
differentiate between sensation and perception;
explain the nature of perception and its scope;
explain the process of perception;
identify the factors affecting perception;
describe the laws of perceptual organization;
summarize the most common types of perceptual constancies; and
explain the basis of perceptual illusion.
2.1 INTRODUCTION
In Block 1, you learned that psychology is the scientific study of behavior and mental
processes. Now in this unit, you will take a closer look of a very important mental
process, that is sensation and perception. Understanding the process of sensation
and perception is very important and psychologists are working closely with experts
in applying the principles to diverse areas like defence, robotics, health, and sports.
So, to understand the process, consider the following example:
You walk in a flower garden and see a beautiful rose, the word comes out from
your mouth ‘how beautiful’, or you walk by the side of a river and see a crocodile,
recognise it and escape. In our daily life we distinguish between two objects, although
the world has dazzling array of objects like humans, animals, houses, plants, etc.
But how do we really do it? How do we know the world around us? Have you
ever thought on this issue? If not, it does not matter!
2.2 SENSATION
The Scottish philosopher Thomas Reid (1710-1796) first distinguished between
sensation and perception. It was explained that sensations are the activities of sense
organs as they are experienced in the consciousness. While as, perception is dependent
on sensation and, different from sensation in that the perceiver is aware of objects
or events in his or her environment. Thus, sensation is the awareness due to stimulation
of a sense organ and perception is the organization and interpretation of sensations.
There are six senses, seeing (eyes), hearing(ears), smelling(nose), touching(skin),
38
taste (tongue), and sense the orientation of body’s positions (proprioception and
,kinesthesia). Our sensory receptors provide us with a variety of visual, tactile, auditory Sensation
and olfactory information. Every sense accomplishes the process of transduction, and Perception
that is the stimuli is detected by the receptor cells, which is then converted to electrical
impulses and then carried to the brain.
Thus, the processes through which we come to experience the stimuli present in the
environment are known as sensation and perception. Human senses translate physical
energy into electrical signals by specialised receptor cells and transmit to our brain via
specialised sensory nerves through which information about our environment is received.
The study of sensation is related to the initial contact between organism and the physical
environment focusing on different forms of sensory stimulation and the input registration
by the sense organs (e.g. the eyes, ears, nose, tongue and skin). Perception is the
process through which we interpret and organise the received information so as to
produce our conscious experience of objects and their relationship. In this process,
physical energy, such as light, sound waves, heat emanating from objects, is transformed
by the concerned sense organs into a code and transferred to and interpreted by the
brain. The line between the two terms sensation and perception, therefore, is somewhat
arbitrary. Sensation typically refers to the direct reception and transmission of messages,
whereas perception refers to the active process of integrating and organising these
sensations.
The relationship between various forms of sensory stimulation (electro-magnetic,
pressure, sound waves) and their registration by sense organs (eyes, tongue, skin, ears)
is the process of sensation. This definition of sensation has the following components:
i) involvement of sense organs of the organism.
ii) presence of stimulus of stimuli in the physical environment
iii) constructing knowledge out of raw material, and
iv) initial contact, i.e. contact without meaning
Take an example: you encounter the pleasant fragrance of a rose. You get the fragrance
through the sense organ ‘nose’. Rose is the stimulus present in the physical environment.
You feel something and it is constructing knowledge out of raw stimulus material. You
just have the initial contact without clear cut knowledge of source, i.e. rose. Feeling up
to this stage is sensation. Imagine some other example of similar nature and try to
understand the meaning of sensation. Sensation is the starting point of knowledge of
presence of any object around us.
2.2.1 Human Senses and Physical Energy
The beautiful sight of sun-rise, the intense “crack” of start of an old motor-cycle, the
smooth touch of a skin of body, the summer heat, the intense cold, the foul odor, the
sweet taste, all these are experienced by us. But how? These are all through different
sense organs. Our sense organs-eyes, ears, skin, nose and tongue – provide sensations
of vision, hearing, skin senses, smell and taste. Physical energy emanates from objects
such as light, sound waves, heat and touch. These physical energies provide different
types of sensations when presented as stimuli. You have known here two things, that is
(i) our senses include vision, hearing, skin senses, smell and taste, (ii) physical energies
emanates from objects such as light, sound waves, heat and touch. In the absence of
physical energies as stimuli, sensation normally does not take place.
2.2.2 Process of Sensation
The process of sensation is very easy to understand. Physical energy, such as light, 39
,
Structure
2.0 Learning Objectives
2.1 Introduction
2.2 Sensation
2.2.1 Human Senses and Physical Energy
2.2.2 Process of Sensation
2.3 Our Senses
2.3.1 Vision
2.3.1.1 Visual Acuity
2.3.1.2 Blind Spot
2.3.2 Hearing
2.3.3 Smell
2.3.4 Taste
2.3.5 Skin Senses
2.3.6 Kinesthetic Sense
2.4 Perception: Nature and Scope
2.5 Stages of Perception
2.6 Theoretical Approaches to Perception
2.7 Laws of Perceptual Organization: Gestalt Principles
2.8 Factors Affecting Perception
2.8.1 Effect of Motivation or Need and Set as Perceptual Determinants
2.8.2 Effect of Expectation or Perceptual Expectancy
2.8.3 Effect of Emotions
2.8.4 Effect of Stimulus Characteristic
2.8.5 Effect of Experience
2.8.6 Effect of Culture
2.9 Perception of Depth and Distance
2.9.1 Monocular Cues
2.9.1.1 Relative Size
2.9.1.2 Texture Gradient
2.9.1.3 Arial Perspective (atmospheric) or Haze
2.9.1.4 Linear Perspective
2.9.1.5 Interposition/Occlusion
2.9.1.6 Accommodation
2.9.1.7 Motion Parallax
2.9.2 Binocular Cues
2.9.2.1 Retinal Disparity (binocular parallax)
2.9.2.2 Covergence
2.10 Movement Perception
* Dr. Arti Singh, Academic Associate of Psychology, IGNOU, New Delhi and Dr. Meetu Khosla,
Associate Professor of Psychology, Daulat Ram College, Delhi University, New Delhi. [Sensation,
adapted from BPC 001, (Professor G.P Thakur, Department of Psychology, M.G. Kashi Vidyapeeth, 37
Varanasi)]
,Perception, Learning 2.11 Size Perception
and Memory
2.12 Error in Perception : Illusion
2.13 Summary
2.14 Key Words
2.15 Review Questions
2.16 References and Suggested Readings
2.17 Reference for Figure
2.18 Online Resources
2.0 LEARNING OBJECTIVES
After reading this unit, you will be able to:
differentiate between sensation and perception;
explain the nature of perception and its scope;
explain the process of perception;
identify the factors affecting perception;
describe the laws of perceptual organization;
summarize the most common types of perceptual constancies; and
explain the basis of perceptual illusion.
2.1 INTRODUCTION
In Block 1, you learned that psychology is the scientific study of behavior and mental
processes. Now in this unit, you will take a closer look of a very important mental
process, that is sensation and perception. Understanding the process of sensation
and perception is very important and psychologists are working closely with experts
in applying the principles to diverse areas like defence, robotics, health, and sports.
So, to understand the process, consider the following example:
You walk in a flower garden and see a beautiful rose, the word comes out from
your mouth ‘how beautiful’, or you walk by the side of a river and see a crocodile,
recognise it and escape. In our daily life we distinguish between two objects, although
the world has dazzling array of objects like humans, animals, houses, plants, etc.
But how do we really do it? How do we know the world around us? Have you
ever thought on this issue? If not, it does not matter!
2.2 SENSATION
The Scottish philosopher Thomas Reid (1710-1796) first distinguished between
sensation and perception. It was explained that sensations are the activities of sense
organs as they are experienced in the consciousness. While as, perception is dependent
on sensation and, different from sensation in that the perceiver is aware of objects
or events in his or her environment. Thus, sensation is the awareness due to stimulation
of a sense organ and perception is the organization and interpretation of sensations.
There are six senses, seeing (eyes), hearing(ears), smelling(nose), touching(skin),
38
taste (tongue), and sense the orientation of body’s positions (proprioception and
,kinesthesia). Our sensory receptors provide us with a variety of visual, tactile, auditory Sensation
and olfactory information. Every sense accomplishes the process of transduction, and Perception
that is the stimuli is detected by the receptor cells, which is then converted to electrical
impulses and then carried to the brain.
Thus, the processes through which we come to experience the stimuli present in the
environment are known as sensation and perception. Human senses translate physical
energy into electrical signals by specialised receptor cells and transmit to our brain via
specialised sensory nerves through which information about our environment is received.
The study of sensation is related to the initial contact between organism and the physical
environment focusing on different forms of sensory stimulation and the input registration
by the sense organs (e.g. the eyes, ears, nose, tongue and skin). Perception is the
process through which we interpret and organise the received information so as to
produce our conscious experience of objects and their relationship. In this process,
physical energy, such as light, sound waves, heat emanating from objects, is transformed
by the concerned sense organs into a code and transferred to and interpreted by the
brain. The line between the two terms sensation and perception, therefore, is somewhat
arbitrary. Sensation typically refers to the direct reception and transmission of messages,
whereas perception refers to the active process of integrating and organising these
sensations.
The relationship between various forms of sensory stimulation (electro-magnetic,
pressure, sound waves) and their registration by sense organs (eyes, tongue, skin, ears)
is the process of sensation. This definition of sensation has the following components:
i) involvement of sense organs of the organism.
ii) presence of stimulus of stimuli in the physical environment
iii) constructing knowledge out of raw material, and
iv) initial contact, i.e. contact without meaning
Take an example: you encounter the pleasant fragrance of a rose. You get the fragrance
through the sense organ ‘nose’. Rose is the stimulus present in the physical environment.
You feel something and it is constructing knowledge out of raw stimulus material. You
just have the initial contact without clear cut knowledge of source, i.e. rose. Feeling up
to this stage is sensation. Imagine some other example of similar nature and try to
understand the meaning of sensation. Sensation is the starting point of knowledge of
presence of any object around us.
2.2.1 Human Senses and Physical Energy
The beautiful sight of sun-rise, the intense “crack” of start of an old motor-cycle, the
smooth touch of a skin of body, the summer heat, the intense cold, the foul odor, the
sweet taste, all these are experienced by us. But how? These are all through different
sense organs. Our sense organs-eyes, ears, skin, nose and tongue – provide sensations
of vision, hearing, skin senses, smell and taste. Physical energy emanates from objects
such as light, sound waves, heat and touch. These physical energies provide different
types of sensations when presented as stimuli. You have known here two things, that is
(i) our senses include vision, hearing, skin senses, smell and taste, (ii) physical energies
emanates from objects such as light, sound waves, heat and touch. In the absence of
physical energies as stimuli, sensation normally does not take place.
2.2.2 Process of Sensation
The process of sensation is very easy to understand. Physical energy, such as light, 39
,
