1.1 Explain The Functional Limitations Of Sense Organs Case Study
Ch. 5 – Sensory, Attentional and Perceptual Processes
1 Explain the functional limitations of sense organs.
Ans. Our sense organs function with certain limitations. E.g. our eyes cannot see things which are very bright or dim. Our senses function within a limited range of stimulation.
In order to be noticed by the sensory receptor, a stimulus needs to be of a suitable intensity to be noticed by the sensory receptor, i.e. it has to carry a minimum value or weight. The minimum value of a stimulus required to activate a given sensory system is called absolute threshold or absolute limen. E.g. the minimum number of sugar granules required to say that water in a glass is sweet will be the AL of sweetness. The AL varies according to individuals …show more content…
and situations. Hence, the number of sugar granules that may produce the experience of ‘sweetness’ in 50 percent of occasions will be called the AL of sweetness.
Also, in order to notice two stimuli as different from each other, there has to be some minimum difference between the values of those stimuli. The smallest difference in the value of two stimuli that is necessary to notice them as different is called difference threshold or difference limen (DL). The DL is the minimum amount of change in a physical stimulus that is capable of producing a sensation difference in 50 percent of the trials.
2 What is meant by light and dark adaptation? How do they take place?
Ans. The process of getting adjusted to different intensities of light is called ‘visual adapatation’.
Light adaptation refers to the process of adjusting to bright light after exposure dim light. Dark adaptation refers to the process of adjusting to dimly illuminated environment after exposure to bright light.
Process of visual adaptation:
Visual adaptation occurs due to certain photochemical processes. The rods have a photo-sensitive chemical substance called rhodopsin. When light causes the molecules of this substance to break down, light adaptation takes place. On the other hand, when light is removed, rhodopsin is regenerated with the help of vitamin A. This is a time consuming process. Thus, dark adaptation is a slower process than light adaptation.
3 What is colour vision and what are the dimensions of colour?
Ans. Light is described in terms of wavelength, not in terms of colour. The visible spectrum lies in the range of 380-780 nm. Colour is a psychological property of our sensory experience. It is created when our brain interprets the information received from the external world. The sun light is a perfect mixture of seven colours just like a rainbow. The colours observed are violet, indigo, blue, green, yellow, orange and red.
Dimensions of colour:
A person with normal colour vision can distinguish more than seven million different shades of colour. There are three basic dimensions of colour:
1 Hue: Hue refers to the name of the colour. It varies with the wavelength and each colour is identified with a specific wavelength. Chromatic colours like blue, green, red etc. are characterised by hue while achromatic colours like white, grey or black are not characterised by hues.
2 Saturation: It refers to the relative amount of hue of a surface. The light of a single wavelength is highly saturated. As different wavelengths are mixed, the saturation decreased. The colour grey is completely unsaturated.
3 Brightness: It is the perceived intensity of light. It varies across both chromatic and achromatic colours. White has the highest and black has the lowest degree of brightness.
4 How does auditory sensation take place?
Ans. Auditory sensation begins when sound enters our ear and stimulates the chief organs of hearing. Ear is the primary receptor of auditory stimuli. Sound is the stimulus for the ears. Sound is produced by the pressure variations in the external environment. Any physical movement disturbs the air and pushes the air molecules back and forth. This causes changes in pressure which spreads outward in the form of sound waves. The sound waves travel at a rate of about 1,100 ft/sec. When these sound waves reach our ears, they initiate changes that trigger the auditory receptors.
The pinna collects the sound vibrations and carries them to the tympanum through the auditory meatus. From the tympanic cavity, they are transferred to the three ossicles: the malleus, incus and stapes. These ossicles increase their strength and transmit them to the inner ear. Here, the cochlea receives the sound waves. Through these vibrations, the endolymph is set in motion, which in turn vibrates the corti. Finally, the impulses reach the auditory nerve. The auditory nerve reaches the auditory cortex where the impulse is interpreted.
5 Define attention. Explain its properties.
Ans. The process through which certain stimuli are selected from a group of others is called attention.
Properties of attention:
1 Selection: A large number of stimuli impose upon our sense organs simultaneously, but we do not notice all of them at the same time. Only a selected few are noticed. We selectively focus only on one or two of the stimuli at one time.
2 Alertness: It refers to an individual’s readiness to deal with stimuli that appear before him/her. E.g. while participating in a race the participants on the starting line are in an alert state, waiting for the whistle to blow in order to run.
3 Concentration: It refers to focusing of awareness on certain specific objects while excluding others for the moment. E.g. In the classroom, a student concentrates on the teacher’s lecture and ignores all sorts of noises.
4 Search: Here, an observer looks for some specified subset of objects among a set of objects. E.g. A parent looks for his son among innumerable boys and girls when he goes to fetch his son.
6 State the determinants of selective attention. How does selective attention differ from sustained attention?
Ans. Determinants of selective attention:
1 External factors:
The size (large), intensity (bright) and motion (moving) of stimuli are important determinants of attention.
Novel and moderately complex stimuli easily get into our focus.
Human photographs are easily paid attention to as compared to photographs of inanimate objects.
Sudden and intense stimuli have an immediate capacity to draw attention.
2 Internal factors:
Motivational factor: It relates to our biological and social needs. E.g. When we are hungry, we notice even a faint smell of food.
Cognitive factors: It includes factors like interest, attitude and preparatory set.
Difference between selective attention and sustained attention:
1 Selective attention is concerned mainly with the selection of a limited number of stimuli or objects from a large number of stimuli. Sustained attention is concerned with concentration.
2 Selective attention refers to our limitation of dealing with only a few stimuli at a given moment of time. Sustained attention refers to our ability to maintain attention on an object or event for longer durations.
3 The determinants of selective attention are external factors like size, intensity, motion, novelty, complexity, intensity, etc., internal factors like motivation and cognition. The determinants of sustained attention are sensory modality, clarity of stimuli, temporal uncertainty and spatial
uncertainty.
7 What is the main proposition of Gestalt psychologists with respect to perception of the visual field?
Ans. The prominent Gestalt psychologists are Kohler, Koffka, and Wertheimer. According to them, we perceive different stimuli as an organised ‘whole’ which carries a definite form. The form of an object lies in its whole, which is different from the sum of their parts. The Gestalt psychologists also indicate that our cerebral processes are always oriented towards the perception of a good figure (pragnanz). This is the reason why we perceive everything in an organized form. Thus, according to the Gestalt psychologists, human beings perceive the world in organised wholes rather than in discrete parts.
The structure of the ear can be divided into three main segments:
(Figure)
1 External ear: It contains two main structures – (i) pinna (ii) auditory meatus
Pinna:
It is a cartilaginous funnel-shaped structure.
It collects sound waves from surroundings.
Auditory meatus:
It is a canal protected by hair and wax.
It carries sound waves from pinna to the tympanum or ear drum.
2 Middle ear:
It starts with the tympanum, a thin membrane highly sensitive to sound vibrations.
The tympanum is followed by the tympanic cavity. It is connected to the pharynx with the help of the Eustachian tube.
The Eustachian tube maintains the air pressure in tympanic cavity.
From the cavity, the sound vibrations pass to three ossicles:
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
These ossicles increase the intensity of sound vibrations about ten times and send them to the inner ear.
3 Inner ear:
It has the structure known as membranous labyrinth.
The membranous labyrinth is
1 Explain the functional limitations of sense organs.
Ans. Our sense organs function with certain limitations. E.g. our eyes cannot see things which are very bright or dim. Our senses function within a limited range of stimulation.
In order to be noticed by the sensory receptor, a stimulus needs to be of a suitable intensity to be noticed by the sensory receptor, i.e. it has to carry a minimum value or weight. The minimum value of a stimulus required to activate a given sensory system is called absolute threshold or absolute limen. E.g. the minimum number of sugar granules required to say that water in a glass is sweet will be the AL of sweetness. The AL varies according to individuals …show more content…
and situations. Hence, the number of sugar granules that may produce the experience of ‘sweetness’ in 50 percent of occasions will be called the AL of sweetness.
Also, in order to notice two stimuli as different from each other, there has to be some minimum difference between the values of those stimuli. The smallest difference in the value of two stimuli that is necessary to notice them as different is called difference threshold or difference limen (DL). The DL is the minimum amount of change in a physical stimulus that is capable of producing a sensation difference in 50 percent of the trials.
2 What is meant by light and dark adaptation? How do they take place?
Ans. The process of getting adjusted to different intensities of light is called ‘visual adapatation’.
Light adaptation refers to the process of adjusting to bright light after exposure dim light. Dark adaptation refers to the process of adjusting to dimly illuminated environment after exposure to bright light.
Process of visual adaptation:
Visual adaptation occurs due to certain photochemical processes. The rods have a photo-sensitive chemical substance called rhodopsin. When light causes the molecules of this substance to break down, light adaptation takes place. On the other hand, when light is removed, rhodopsin is regenerated with the help of vitamin A. This is a time consuming process. Thus, dark adaptation is a slower process than light adaptation.
3 What is colour vision and what are the dimensions of colour?
Ans. Light is described in terms of wavelength, not in terms of colour. The visible spectrum lies in the range of 380-780 nm. Colour is a psychological property of our sensory experience. It is created when our brain interprets the information received from the external world. The sun light is a perfect mixture of seven colours just like a rainbow. The colours observed are violet, indigo, blue, green, yellow, orange and red.
Dimensions of colour:
A person with normal colour vision can distinguish more than seven million different shades of colour. There are three basic dimensions of colour:
1 Hue: Hue refers to the name of the colour. It varies with the wavelength and each colour is identified with a specific wavelength. Chromatic colours like blue, green, red etc. are characterised by hue while achromatic colours like white, grey or black are not characterised by hues.
2 Saturation: It refers to the relative amount of hue of a surface. The light of a single wavelength is highly saturated. As different wavelengths are mixed, the saturation decreased. The colour grey is completely unsaturated.
3 Brightness: It is the perceived intensity of light. It varies across both chromatic and achromatic colours. White has the highest and black has the lowest degree of brightness.
4 How does auditory sensation take place?
Ans. Auditory sensation begins when sound enters our ear and stimulates the chief organs of hearing. Ear is the primary receptor of auditory stimuli. Sound is the stimulus for the ears. Sound is produced by the pressure variations in the external environment. Any physical movement disturbs the air and pushes the air molecules back and forth. This causes changes in pressure which spreads outward in the form of sound waves. The sound waves travel at a rate of about 1,100 ft/sec. When these sound waves reach our ears, they initiate changes that trigger the auditory receptors.
The pinna collects the sound vibrations and carries them to the tympanum through the auditory meatus. From the tympanic cavity, they are transferred to the three ossicles: the malleus, incus and stapes. These ossicles increase their strength and transmit them to the inner ear. Here, the cochlea receives the sound waves. Through these vibrations, the endolymph is set in motion, which in turn vibrates the corti. Finally, the impulses reach the auditory nerve. The auditory nerve reaches the auditory cortex where the impulse is interpreted.
5 Define attention. Explain its properties.
Ans. The process through which certain stimuli are selected from a group of others is called attention.
Properties of attention:
1 Selection: A large number of stimuli impose upon our sense organs simultaneously, but we do not notice all of them at the same time. Only a selected few are noticed. We selectively focus only on one or two of the stimuli at one time.
2 Alertness: It refers to an individual’s readiness to deal with stimuli that appear before him/her. E.g. while participating in a race the participants on the starting line are in an alert state, waiting for the whistle to blow in order to run.
3 Concentration: It refers to focusing of awareness on certain specific objects while excluding others for the moment. E.g. In the classroom, a student concentrates on the teacher’s lecture and ignores all sorts of noises.
4 Search: Here, an observer looks for some specified subset of objects among a set of objects. E.g. A parent looks for his son among innumerable boys and girls when he goes to fetch his son.
6 State the determinants of selective attention. How does selective attention differ from sustained attention?
Ans. Determinants of selective attention:
1 External factors:
The size (large), intensity (bright) and motion (moving) of stimuli are important determinants of attention.
Novel and moderately complex stimuli easily get into our focus.
Human photographs are easily paid attention to as compared to photographs of inanimate objects.
Sudden and intense stimuli have an immediate capacity to draw attention.
2 Internal factors:
Motivational factor: It relates to our biological and social needs. E.g. When we are hungry, we notice even a faint smell of food.
Cognitive factors: It includes factors like interest, attitude and preparatory set.
Difference between selective attention and sustained attention:
1 Selective attention is concerned mainly with the selection of a limited number of stimuli or objects from a large number of stimuli. Sustained attention is concerned with concentration.
2 Selective attention refers to our limitation of dealing with only a few stimuli at a given moment of time. Sustained attention refers to our ability to maintain attention on an object or event for longer durations.
3 The determinants of selective attention are external factors like size, intensity, motion, novelty, complexity, intensity, etc., internal factors like motivation and cognition. The determinants of sustained attention are sensory modality, clarity of stimuli, temporal uncertainty and spatial
uncertainty.
7 What is the main proposition of Gestalt psychologists with respect to perception of the visual field?
Ans. The prominent Gestalt psychologists are Kohler, Koffka, and Wertheimer. According to them, we perceive different stimuli as an organised ‘whole’ which carries a definite form. The form of an object lies in its whole, which is different from the sum of their parts. The Gestalt psychologists also indicate that our cerebral processes are always oriented towards the perception of a good figure (pragnanz). This is the reason why we perceive everything in an organized form. Thus, according to the Gestalt psychologists, human beings perceive the world in organised wholes rather than in discrete parts.
The structure of the ear can be divided into three main segments:
(Figure)
1 External ear: It contains two main structures – (i) pinna (ii) auditory meatus
Pinna:
It is a cartilaginous funnel-shaped structure.
It collects sound waves from surroundings.
Auditory meatus:
It is a canal protected by hair and wax.
It carries sound waves from pinna to the tympanum or ear drum.
2 Middle ear:
It starts with the tympanum, a thin membrane highly sensitive to sound vibrations.
The tympanum is followed by the tympanic cavity. It is connected to the pharynx with the help of the Eustachian tube.
The Eustachian tube maintains the air pressure in tympanic cavity.
From the cavity, the sound vibrations pass to three ossicles:
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
These ossicles increase the intensity of sound vibrations about ten times and send them to the inner ear.
3 Inner ear:
It has the structure known as membranous labyrinth.
The membranous labyrinth is