Unit 5- Sensation and Perception

Question 1

A neuron

Answer 1

A Neuron is a specialized cell that transmits neural impulses or messages to other neurons, glands and muscles. Although neurons may have different shapes and sizes, they are basically the same with common characteristics. When a neural impulse travels down the axon it arrives at the terminal buttons and triggers the secretion of a neurotransmitter.

Question 2

The Axon

Answer 2

is a slender tube that extends from the cell body or Soma and transmits these messages to other neurons or to muscles and glands.

Question 3

Synaptic Terminals

Answer 3

At the end of the axon is a division into tiny branches that end with small swellings

Question 4

Synapse

Answer 4

There is a slight gap between the terminal button and the cell body of the neuron.

Question 5

A neurotransmitter

Answer 5

is a chemical that diffuses across the synapse and stimulates the next neuron, thereby transmitting the message as an impulse from one neuron to the next.

Question 6

Dendrites

Answer 6

There are a number of branches which receive neural impulses or messages from adjacent neurons.

Question 7

Three categories of neurons

Answer 7

Neurons are classified into three (3) categories depending on their general function.
1. Sensory Neurons - transmit impulses received by receptors, to the central nervous system. The Receptors are specialized cells in the sense organs, muscles, skin and joints that detect physical or chemical changes. These
changes are turned into impulses that travel along the sensory neuron.
2. Motor Neurons - carry out-going signals from the brain or spinal cord to muscles and glands.
3. Inter-neurons - receive signals from the sensory neurons and send impulses to other inter-neurons or to motor neurons. These are found only in the brain, spinal cord and eyes.

Question 8

A nerve

Answer 8

is a bundle of elongated axons belonging to hundreds or thousands of neurons. The cell bodies of the neurons are generally grouped together throughout the nervous system.

Question 9

An Action-Potential

Answer 9

is an electro-chemical impulse that travels from the cell body down to the end of the axon. Each action potential is the result of electrically charged molecules in and out of the cell. When an action potential travels down an axon, it causes the terminal buttons to release the neurotransmitters. Neurotransmitters can either excite or inhibit the firing of the following neuron and the message can be passed on.

Question 10

Reflex action

Answer 10

An example of a simple neural circuit is a Reflex Action. A simple withdrawal reflex which is triggered by an unpleasant stimulus like touching a hot pot requires the three types of neurons. Sensory neurons detect the noxious stimulus and convey the message to the spinal cord. Inter-neurons located entirely within the brain and spinal cord, receive the sensory information and in turn stimulate the motor neurons that cause the appropriate muscles to contract.

Question 11

Central Nervous System

Answer 11

The entire nervous system is inter-related even though it is divided. The Central Nervous System includes all the neurons in the brain and spinal cord.

Question 12

Peripheral Nervous System

Answer 12

contains the nerves connecting the brain and spinal cord to the other parts of the body. The peripheral system is further subdivided into the Somatic System which carries messages to and from the sense receptors, muscles and the surface of the body;

Question 13

The Autonomic System

Answer 13

The autonomic nervous system controls glands and the smooth muscles including the heart, the blood vessels and the lining of the stomach and intestines. The autonomic nervous system gets its name from the fact that many of the activities it controls like respiration, and circulation are self-regulatory, even when a person is asleep or unconscious. The autonomic nervous system is further subdivided into the sympathetic and parasympathetic nervous systems.

Question 14

Sympathetic and Parasympathetic system

Answer 14

The Sympathetic System is typically active during times of arousal and the Parasympathetic System is associated with rest. Most nerve fibres connecting various parts of the body to the brain are gathered at the spinal cord where the bony spinal vertebrae protect them.

Question 15

Sensory and Motor nerves

Answer 15

The Sensory Nerves of the somatic system transmit information about external stimuli from the skin, muscles and joints to the central nervous system, which allows us to feel pain, pressure, and changes in temperature. The Motor Nerves of the somatic system carry impulses from the central nervous system to the muscles where they initiate action.

Question 15

The Brain

Answer 15

There are many different ways the brain can be subdivided. One way is in two similar mirror image halves. These two symmetrical right and left halves control the side of the body opposite to their location. The Left Hemisphere generally controls the right side of the body and the Right Hemisphere of the brain, the left side of the body. Thus, damage to the right side of the brain is typically indicated by functional difficulties in the left side of the body. Lateralization is the dominance of one hemisphere of the brain in a specific function. For example, for most people, language is lateralized in the left hemisphere.

Question 15

Chromosomes and genes

Answer 15

Natural selection operates on genes, which are segments of deoxyribonucleic acid (DNA) molecules that form the fundamental hereditary unit. The genes we received from our parents and transmit to our offspring are carried by chromosomes-structures in each cell body. Each gene gives the cell coded instructions directing them to perform a specific function. Genes exist in pairs so a child receives half from each parent’s total genes. Two human beings, even siblings are extremely unlikely to inherit the same set of genes (except for multiples e.g. twins). Either genes of a gene pair can be dominant or recessive. When both members of a gene pair are dominant, the individual manifests the form of the trait specified by these dominant genes. If one is dominant and the other recessive, the dominant gene determines the form of the trait. Only if the genes contributed by both parents are recessive then the recessive trait is expressed. e.g. blue eyes, albinism, and haemophilia. Of special psychological interest are diseases as Huntington’s Disease (HD) and Phenylketonuria (PKU), both of which involve deterioration of the nervous system and associated behavioural and cognitive problems. Single genes determine some traits, but many genes contribute to most human characteristics - they are polygenetic. What happens to this genetic potential depends on environmental conditions, e.g. genes may predispose a person to schizophrenia but the environment in which he/she grows up in shapes the actual outcome.

Question 16

Genes, Behaviour and Evolution

Answer 16

All biological organisms have evolved over millions of years and environmental factors have played important roles in shaping the organisation and functions of the nervous system. The field of Behaviour Genetics combines the methods of genetics and psychology to study the inheritance of behavioural characteristics. It is known that the physical characteristics like hair, eye colour and height are inherited. Behavioural Geneticists study the degree to which psychological characteristics like mental ability, emotional stability and temperament are passed from parent to offspring. Social context also powerfully modulate the nature and pattern of behaviour.

Question 17

Define sensation

Answer 17

A sensation is a detection of simple stimuli, such as brightness, color, warmth and sweetness. It is a passive process of bringing information from the outside world into the body and to the brain. The process is passive as we do not have to be consciously engaging in the sensing process.

Question 18

When does sensation occur

Answer 18

A sensation occurs - when the sensory mechanisms (the visual, the auditory, the gustatory, the olfactory and the somatosensory systems) absorb energy from a physical stimulus in the environment. The sensory receptors convert this energy into neural impulses and send them to the brain.

Question 19

Different senses

Answer 19

The different senses include touch - which involves pressure, temperature and pain; vision, hearing, smell, and taste.

Question 20

Define sensitivity

Answer 20

The more intense a stimulus, the more strongly it affects the relevant sense organ. A basic way of assessing the sensitivity of a sensory modality is to determine the absolute threshold.

Question 21

Absolute Threshold

Answer 21

is the minimum magnitude of a stimulus that can be reliably discriminated from no stimulus at all. Our sensory modalities are extremely sensitive to the presence of or a change in an object or event.

Question 22

Characteristics of sensory modalities

Answer 22

Two characteristics are common to all sensory modalities. Sensitivity describes sensory modalities at a psychological level and Sensory Coding describes sensory modalities at a biological level

Question 23

Sensory coding

Answer 23

How stimuli are transmitted from the sensory receptors to the brain. Each sense responds to a certain kind of stimulus - light energy for vision, mechanical energy for hearing and touch; chemical energy for taste and smell. Sensory modality must first perform Transduction - the translation of physical energy into electrical signals that can make their way to the brain. This is accompanied by specialized cells in the sense organs called Receptors. For example the receptors for vision are located in the thin layer of tissue on the inside of the eye, the receptors for hearing are fine hair cells located deep in the ear and the vibrations in the air bend these hair cells to create neural impulses. A receptor is a specialized neuron. When activated passes it passes an electrical signal to connecting neurons. The signal travels until it reaches its receiving area in the cortex, with different sensory modalities sending signals to different receiving areas. Somewhere in the brain the electrical signal results in the conscious sensory experience.

Question 24

Properties of any stimulus

Answer 24

Two properties of any stimulus are its Intensity or how strong the stimulus is, and its Quality or what the stimulus is like. It would also be useful to know the duration, location and time of onset of the stimulus. Each of our sensory systems provides some information about these attributes. The receptors and their neural pathways to the brain must therefore code for all these qualities especially intensity and quality.
Coding for the quality of a stimulus is more complex.

Question 25

Means of coding

Answer 25

The primary means of coding the intensity of a stimulus is via the number of neural impulses on each unit and time - that is the rate of neural impulses. In general, the greater the intensity of the stimulus, the higher the neural firing rate, and the greater the firing rate, the greater the perceived magnitude of the stimulus.

Question 26

the brain could distinguish between information for different sensory modalities

Answer 26

Johannes Müller (1825) suggested that the brain could distinguish between information for different sensory modalities like light and sound-because they involve different sensory nerves. We now know that the brain codes the qualitative differences between sensory modalities according to the specific neural pathways involved. Neural pathways originating in different receptors terminate in different areas of the cortex. For example we can distinguish between sweet and sour tastes because each kind of taste has its own nerve fibres.

Question 27

What does a sensory system use to code the quality of a sensation

Answer 27

A sensory system may also use the pattern of neural firing to code the quality of a sensation. A particular fibre may respond maximally to a sweet taste, but it may respond to other tastes at varying degrees. One fibre may respond best to sweet tastes, less to bitter tastes and even less to salty tastes. A sweet tasting stimulus would thus lead to activity in a large number of nerve fibres, with some firing more than others. This might be the neural pattern of coding for a sweet taste while a different pattern would be the code for bitter tastes.

Question 28

Vision

Answer 28

is the most finely tuned sense that can obtain information for humans at a distance. Smell and hearing are also capable of gathering information for us at a distance.

Question 29

What is the physical stimulus for vision

Answer 29

Light is a form of electromagnetic energy that emanates from the sun and the rest of the universe. Electromagnetic energy also includes radio and tv waves, x-rays, ultra-violet and infrared rays. These all travel at varying wavelengths; our eyes are sensitive to only a small portion of electromagnetic energy.

Question 30

Retina

Answer 30

a thin layer of tissue at the back of the eyeball.

Question 31

Cornea

Answer 31

which is the transparent surface of the eye,

Question 32

Pupil

Answer 32

is a circular opening whose diameter varies in response to the level of light presented.

Question 33

How do we see or form images

Answer 33

For the image forming systems light is reflected from the object to form an image on the retina The image forming system consists of the cornea, the pupil and the lens. Light enters the Cornea and rays are bent inward by it to begin the formation of the image. At different distances the Lens changes shape to focus on an object. The lens completes the process of focusing the light on the retina. The lens becomes more spherical for near objects and flatter for far ones. The Pupil, a circular opening whose diameter varies in response to the level of light presented. It is largest in dim light and smallest in bright light, which helps enough light to pass through the lens to maintain image quality at different light levels.

Question 34

Transduction

Answer 34

At the retina, where these other components focus the image, the Transduction systems take over

Question 35

Two types of receptors

Answer 35

Rods and cones

Question 36

Rods

Answer 36

are specialised for seeing at night - they operate low intensities and lead to low resolution, colourless sensation.

Question 37

Cones

Answer 37

are best for seeing during the day - they respond to high intensities and result in high-resolution sensations that include colour.

Question 38

Fovea

Answer 38

When we want to see the details of an object we move our eyes so that the object is projected onto the Fovea, which is a small region at the centre of the retina. At the fovea is the most densely packed group of receptors. The high- density fovea is therefore the highest resolution part of the eye that is best at seeing details.

Question 39

Tranduscing light

Answer 39

For the receptors to transduce the light reflected off an object into electrical impulses the rods and cones must contain chemicals that absorb light. This absorption of light starts the process that eventuates in a neural impulse

Question 40

After transduction and ganglion cells

Answer 40

Once transduction is completed the electrical impulses must make their way to the brain via connecting neurons. Some of these are called Ganglion Cells with long axons which come together to form the Optic Nerve that leads to the brain.

Question 41

The blind spot

Answer 41

At the optic nerve are no receptors so at this region we are blind. This is called the blind spot.

Question 42

Deafness

Answer 42

Most people consider the sense of hearing as second in importance to vision. Deafness however, is more likely to create social isolation than blindness. Although our eyes transmit more information to our brains, our eyes are used for some of the most important forms of social communication.

Question 43

The Outer Ear or Pinna

Answer 43

functions as an outside, reverse megaphone designed to collect and bring sounds into the internal parts of the ear. The location of the outer ear, on either side of the head helps with sound location. This is the process by which we identify the origins of a sound. Wave patterns in the air enter the ear at a slightly different time permitting the brain to use the discrepancy to locate the place from which sound is originating.

Question 44

Sound

Answer 44

Sound is the movement of air molecules brought about by the vibrations of an object. Sound travels through the air in wave patterns arriving at the outer ear in the form of wave vibrations and funnel into the Auditory Canal. This is a tube like passage that leads to the eardrum. The Eardrum operates like a miniature drum vibrating when sound waves hit it

Question 45

Middle Ear

Answer 45

The more intense the sound the more the eardrum vibrates. These vibrations are then transmitted into the Middle Ear. This chamber contains three (3) bones, named because of their shapes Hammer/ Mallues, Anvil/ Incus and Stirrups/Stapes. These bones one function is to transmit vibrations only with an increased strength from the eardrum to the Oval Window. The middle ear therefore acts as a tiny amplifier making us aware of sounds that would otherwise go unnoticed.

Question 46

The Inner Ear

Answer 46

is the portion of the ear that changes the sound vibrations into a form that allows them to be transmitted to the brain. It also contains the organs that allow us to locate our position and determine how we are moving through space. When sound enters the inner ear through the oval window, it moves into the Cochlea, a coiled tube filled with fluid that looks something like a snail. Inside is the Basilar Membrane a structure that runs through the centre of the cochlea dividing it into an upper and lower chamber. It is covered with hair cells. When they are bent by vibrations entering the cochlea, the neural message is transmitted to the brain.

Question 47

Bone Conduction/ Why you sound different to yourself than to other people who hear your voice

Answer 47

There is an additional method of entry for sound that is Bone Conduction. Because the ear rests on a maze of bones within the skull the cochlea is able to pick up subtle vibrations that travel across the bones from other parts of the head (& body). One of the ways you hear your own voice is through bone conduction. This explains why you sound different to yourself than to other people who hear your voice.

Question 48

Physical Aspects of Sound

Answer 48

Physical Aspects of Sound
. Frequency- this is the number of wave crests that occur in a second. With very low frequencies there are relatively few crests and therefore slower up and down wave cycles per second. Pitch is the characteristic that makes sounds high or low. Higher frequencies translate into higher pitches.
Timbre is what makes a particular sound unique from another sound. For instance, it is the difference between a guitar and a piano playing the same note at the same volume.
Tone refers to sound that can be recognized by its regularity of vibration.

Question 49

Theories of Sound

Answer 49

The Place Theory of Hearing
The Frequency Theory of Hearing

Question 50

The Place Theory of Hearing

Answer 50

The Place Theory of Hearing sound affects different areas of the basilar membrane depending on the frequency of the sound waves. The part of the basilar membrane that is nearest to the oval window is the most sensitive to higher frequency sounds. While the part that is nearest to the cochlea’s inner end is most sensitive
to low frequencies. The place theory of hearing suggests that different areas of the basilar membrane respond to different frequencies.

Question 51

The Frequency Theory of Hearing

Answer 51

suggests that the entire basilar membrane acts like a microphone by vibrating as a whole in response to a sound. The nerve receptors send out signals that are tied directly to the frequency of the sound to which we are exposed. The number of nerve impulses is a direct function of the sound frequency. The higher the pitch of a sound and therefore the greater the frequency of its wave crests the greater the number of impulses that are transmitted up the auditory nerve to the brain. Because our eyes and ears are so important to us in our day-to-day lives, many efforts have been made to develop replacements for individual who suffered ir-repairable damage to these organs.

Question 52

Balance

Answer 52

Several structures of the ear are related more to our sense of balance than our hearing. The Semi circular Canals of the inner ear consist of three tubes containing fluid that sloshes around through them when the ear moves signalling rotational or angular movement of the brain. The pull of our bodies caused by acceleration forward, backward; or up and down motion, as well the constant pull of gravity is sensed by the Otholiths. These are tiny motion sensitive crystals within the semi-circular canals. When we move these crystals shift like sands on a windy beach.

Question 53

Smell

Answer 53

The volatile molecules given off by a substance are stimuli for smell. The molecules leave the substance, travels through the air and enters the nasal passage way. The molecules must also be soluble in fat because the receptors for smell are covered with a fat like substance. The receptors for smell are located high on the nasal cavity. When the Cilia or hair like structures of these receptors come into contact with volatile molecules, an electrical impulse results. The impulse travels along nerve fibres to the olfactory bulb, a region in the brain that lies just below the frontal lobes. The olfactory bulb in turn is connected to the olfactory cortex on the inside of the temporal lobes. There is a direct connection between the olfactory bulb and the part of the cortex known to be involved in the formation of long-term memory. A distinctive smell can be powerful in retrieving an old memory.

Question 53

Taste

Answer 53

The sense of taste seems to be satisfied with only four (4) basic receptor cells. These specialised cells are sweet, sour, salt and bitter. Every other taste is simply a combination of these 4 basic qualities. The receptor cells for taste are located on the taste buds, which are distributed across the tongue. The distribution is uneven and certain areas of the tongue are more sensitive than others. The tip of the tongue is most sensitive to sweetness. Only the sides are very sensitive to sour tastes. The rear specialises in bitter tastes and salt is located along the sides of the tongue. Since different taste areas on the tongue correspond to different areas in the brain, neurons responding to sour and bitter tastes are located in a different region as compared to sweet tastes. In contrast, salt tastes stimulate neurons that are distributed across the entire area of the brain.

Question 54

The Somatosenses

Answer 54

The Somatosenses / Skin Senses
Traditionally touch was thought to be a single sense, today it includes three (3) distinct skin senses:
Pressure
Temperature
Pain

Question 55

Pressure

Answer 55

The stimulus of sense pressure is physical pressure on the skin. We can discriminate among variations in pressure over the surface of the body. Some parts of the body are more sensitive than others in sensing the intensity. The lips, nose and cheeks are the most sensitive. The difference in the sensing of pressure is closely linked to the number of receptors that respond to the stimulus at each of those locations. Sensations of pressure only occur when the skin is actually moving. The pressure detector responds only when being bent. Sensation of pressure ceases when movement ceases.

Question 56

Temperature

Answer 56

The stimulus for temperature is the temperature of our skin, the receptors are on the neurons just below the skin. Different sensory endings produce sensations of warmth and coolness. Detectors for coolness appear to be closer to the surface of the skin. In the transduction stage cool receptors generate a neural impulse when there is a decrease in skin temperature. Warm receptors generate an impulse when there is an increase in temperature. Because maintaining body temperature is crucial to survival, we must be able to detect small changes in our skin temperature.

Question 57

Pain

Answer 57

Of all our senses none captures our attention as pain. It is hard to ignore. We will be at risk without a sense of pain. Some people are born with a rare genetic disorder called Congenital Insensitivity to Pain, which makes them unable to feel pain and they typically die young due to tissue deterioration resulting from wounds that could have been avoided had they been able to feel pain. Pain is a complex sensation involving not only the intense sensory stimulation but also an emotional component.

Question 58

Two types of pain

Answer 58

Phasic Pain or the type of pain we feel immediately upon receiving an injury. It is bright and sharp.
Tonic Pain is the deep dull pain that sometimes follows. It is longer lasting pain occurring after an injury has occurred. Different types of axons mediate these two (2) types of pain. They have their own neural pathways eventually reaching different parts of the cortex. Pain or the fear of pain is one very strong motivator of human behaviour.

Question 59

The Gate Control Theory of Pain

Answer 59

According to this theory the sensation of pain requires not only that pain receptors on the skin be active, but also that neural gateways in the spinal cord are open. This allows for the signals from the pain receptors to be transmitted to the brain. Because the neural gateway can be closed by signals sent down the cortex, the perceived intensity of pain can be reduced by the person’s mental state. In other words “mind over matter”.

Question 60

Internal Senses

Answer 60

Sensory endings located in our internal organs, bones, joints and muscles convey painful neural and in some cases pleasurable sensory information e.g. the pain of arthritis and the pleasure of a warm drink descending to our stomach. Muscles contain special sensory endings and another set of stretch detectors consist of spindle shaped receptors called
spindle muscles. These inform the brain changes in muscle length. The brain uses this information from muscles and joints to keep track of the location of body parts and to control muscular contractions.

Question 61

Perception

Answer 61

is the detection of objects (both animate and inanimate), their locations, their movements and their backgrounds. It is the active process of selecting, organizing, and interpreting the information brought to the brain by the senses.

Question 62

Example of sensation and perception

Answer 62

According to these definitions, seeing the color red is a sensation but seeing a red apple is a perception. Similarly, seeing a movement is a sensation, but seeing a baseball coming toward us and realizing that we need to move to the left to catch it is a perception

Question 63

How does perception occur

Answer 63

when the brain organizes the information and translates it into something meaningful.

Question 64

Attention

Answer 64

\Whatever the task only a tiny portion of the incoming stream of information is relevant to it. If the vast majority is irrelevant this implies that the sensory system and the brain must have some means of screening the incoming information. Only the information relevant to the task at hand is allowed through and irrelevant information is filtered out. The sum total of all these filters. We direct our attention to objects of interest to us by physically reorienting our sensory receptors e.g. with vision this means moving our eyes until the object of interest falls on the fovea.
Attention is multi-modal meaning it can move within a modality or between modalities. We are consciously unaware of and remember little if anything about non-attended information. There is now considerable evidence that our perceptual system processes non-attended stimuli to some extent, even though those stimuli rarely reach consciousness. Therefore, lack of attention does not block messages entirely; rather it Attenuates them much like a volume control that is turned down but not off.

Question 65

Perceptual Organisation

Answer 65

We do not just passively resolve to visual stimuli that happen to fall on our retinas, instead we actively try to organise and make sense of what we see. Perception is a constructive process by which we go beyond the stimuli that are presented to us and attempt to construct a meaningful situation.

Question 66

Gestalt Laws of Organisation

Answer 66

German psychologists discovered a number of important principles that are valid for the interpretation of visual and auditory stimuli.

Closure - groupings are usually made in terms of enclosed or complete figures rather than open ones.

Question 67

Proximity

Answer 67

elements that are closer together are grouped together.

Question 68

Similarity

Answer 68

elements that are similar in appearance are grouped together.

Question 69

Simplicity

Answer 69

this is the overriding Gestalt Principle. When we observe a pattern we perceive it in the most basic, straightforward way we can. Two (2) objects that form a whole is the simplest combination.

Question 70

Perception of stimuli

Answer 70

Perception of stimuli in our environment goes well beyond the individual elements that we sense, instead it represents an active construction process carried out within the brain. There, bits and pieces of sensation are put together to make something greater and more meaningful than the separate elements. The whole therefore is quite different from the sum of the individual elements.

Question 71

Perceptual Constancy

Answer 71

is a phenomena in which physical objects are perceived as constant despite changes in their appearance or in the physical environment.
Perceptual Constancy occurs not just in terms of size but with shape and colour as well. The image on our retina varies as a plane approaches, flies overhead, and disappears, yet we do not perceive the plane as changed in shape; instead we perceive it as unchanging despite the physical variations that occur.

Question 72

Perception and Communication

Answer 72

In living our lives and communicating with each other our perception of reality is less important than reality itself. Some would argue that there IS no ultimate reality, only the illusion of our perceptions.
Our perceptions are influenced by:
physical elements - what information your eye or ear can actually take in, how your brain processes it.
environmental elements - what information is out there to receive, its context.
⚫ learned elements - culture, personality, habit: what filters we use to select what we take in and how we react to it.

Question 73

Perception in Intrapersonal relationships

Answer 73

What influences your interpersonal perceptions?
Your underlying belief that as far as personality go, some characteristics must accompany others and therefore when you see one characteristic in someone you expect to see certain others.
When you label others as being a certain way, this can create a self-fulfilling prophecy which can influence the behaviour of others.
You may perceive what you want to see instead of what exists. -We tend to want to see consistent information. When perceiving, we look for consistent info and tend to ignore inconsistent info. Stereotypes, or fixed impressions of a group of persons may influence your perception of individual members of that group. You may judge them as members of the group and not as an individual.

Question 74

Increasing Accuracy in Interpersonal Perception

Answer 74

How might you increase your accuracy in perception?
Perceive critically: For example, recognize your role in perception, avoid early conclusions, and avoid mind reading.
Check your perceptions: describe what you see or hear and ask for confirmation.
Reduce uncertainty: For example, by lurking before actively participating in an Internet chat group, collecting information about the person or situation, interacting and observing the situation.
Be culturally sensitive: recognize the differences between you and others and also the differences among people from another culture.

Question 75

Selective Attention

Answer 75

is a process of discriminating between what is important and what is irrelevant and is influenced by motivation. It is necessary as one’s eyes cannot absorb all the visual stimuli around them. Selective attention is given to relevant visual stimuli. e.g. Students in a class should focus on what the teacher is saying and what is being presented. Students walking into the classroom may focus on people in the classroom, what the teacher is wearing etc.
Visual scanning, takes the form of fixations - brief periods during which the eyes are relatively stationary, separated by saccades (quick jumps of the eye from one place to another). Visual fixations are not random, but occur at the areas of the scene which contain the most information. An example of this can be observed when a person looks at a face, many fixations are observed on the eyes, nose and mouth features that most efficiently distinguish one face from another.

Question 76

Perceptual Expectancy

Answer 76

is how we perceive the world

Question 77

Psychophysics

Answer 77

is the study of how physical stimuli are translated into psychological experience. The systematic study of the relationship between the physical characteristics of the stimuli and the sensation they produce. In order to measure these events, psychologists use THRESHOLDS

Question 78

Thresholds

Answer 78

A threshold is a dividing line between what has detectable energy and what does not. e.g. some rooms have automatic light sensors. When people have not been in a room for a while, the lights go out. Difference Thresholds holds the minimum amount of stimulus intensity change needed to produce a notable change. The greater the intensity (e.g. weight) of a stimulus the greater the change needed to produce a notable change

Question 79

Signal Detection Theory

Answer 79

Theory states that detection of a stimulus involves some decision making process as well as a sensory process. Both sensory and decision making processes are influenced by many more factors than just intensity. e.g. you are having a party and order delivery, you need to pay attention so that you detect the appropriate signal (door bell) as there is a lot of noise at the party.

Question 80

Sight and Vision

Answer 80

The visual system performs a remarkable job. It works on sensing and perceiving light waves. Light waves vary in length and amplitude. We take for granted that in a quick glance we can recognize what there is to see: people, objects, landscape in depth and color.

To perceive distance, the retina is a vital part of the human eye. The retina is a two dimensional surface on to which a three dimensional world is projected. It reflects height and width, but depth information is lost and must be reclaimed with the assistance of depth cues. Depth cues are Binocular and Monocular and there are also muscular cues to be taken into account in examining visual perception.

Question 81

Binocular cues

Answer 81

is a term of reference to cues in relation to the use of both eyes. Humans have two eyes, rather than just one. This enables one, using the tool of binocular disparity, to perceive depth. Binocular disparity is the difference in view seen by each separate eye and provides one with two separate sets of information to judge depth with. Binocular cues are of limited usefulness, as it can only serve the observer to judge depth in objects that are relatively close.

Question 82

Monocular Cues

Answer 82

are useful in the perception of far away objects e.g. mountains and tall buildings. Some monocular cues are relative size, relative height, perspective, shading and shadows and relative motion.

Question 83

Muscular Cues

Answer 83

are also called accommodation. The eyes accommodate or converge to bring a target or object into visual focus. The muscles which are attached to the lens perform the focusing, contraction and expansion of the pupil (of the eye) all to aid in the effort of accommodation.

Question 84

Continuity

Answer 84

states that we follow where we are led. Dots in a smooth curve appear to go together more than jagged angles.

Question 85

Difference between sensation and perception (long version)

Answer 85

Sensations are usually taken for granted. They concentrate on the reception of information coming to a person from the environment. Stimuli are picked up and conducted to the perceptual systems of the human body through the presence and actions of receptors. Sensory receptors are the eyes, ears, nose, tongue and skin. Sensation may be classified into the following types – visual sensation, gustave sensation, auditory sensation, olfactory sensation and the sensation of touch, primarilary those of pressure and pain. Sensation is composed of transmission of information about one’s environment.

Perception is concerned with the transduction of the information obtained via sensation. Transduction refers to the changing of energy from one form to another and is the way information from environmental stimuli is processed. It is the neural activity that follows sensation and incorporates both the process of transduction and the process whereby the presence of stimuli leading to neural activity through transmission. These two processes occur instantaneously. Perception may be of the following types visual, olfactory, auditory and the perceptions of touch, especially with regards to pressure and pain.

Question 86

Difference between sensation and perception (short difference)

Answer 86

SENSATION IS CONCERNED MORE WITH TRANSMISSION AND PERCEPTION IS CONCERNED MORE WITH TRANSDUCTION. BOTH THESE PROCESSES ARE VITALLY LINKED TO EACH OTHER AND ARE NECESSARY FUNCTIONS OF THE HUMAN BODY.