Sensations can be defined as the passive process of bringing information from the outside world into the body and to the brain. The process is passive in the sense that we do not have to be consciously engaging in a "sensing" process.
How sensation and perception work together: Sensation occurs: sensory organs absorb energy from a physical stimulus in the environment. sensory receptors convert this energy into neural impulses and send them to the brain. Perception follows: the brain organizes the information and translates it into something meaningful.
In order to measure these events, psychologists use THRESHOLDS.
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Threshold - a dividing line between what has detectable energy and what does not. Difference Threshold - the minimum amount of stimulus intensity change needed to produce a noticeable change. the greater the intensity (ex., weight) of a stimulus, the greater the change needed to produce a noticeable change.
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Signal-Detection Theory - detection of a stimulus involves some decision making process as well as a sensory process. Additionally, both sensory and decision making processes are influenced by many more factors than just intensity. Noise - how much outside interference exists. Criterion - the level of assurance that you decide must be met before you take action.
The Nature of Sensory Processes
Sensory Thresholds
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Absolute threshold
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Sensory adaptation
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Difference threshold (just noticeable difference) the minimum amount of stimulus intensity change needed to produce a noticeable change. the greater the intensity (ex., weight) of a stimulus, the greater the change needed to produce a noticeable change.
Visual sense the visual system works on sensing and perceiving light waves. Light waves vary in their length and amplitude.
Structure of The EYE: 1.
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Cornea - the round, transparent area that allows light to pass into the eye. Lens - the transparent structure that focuses light onto the retina. Retina - inner membrane of the eye that receives information about light using rods and cones. The functioning of the retina is similar to the spinal cord - both act as a highway for information to travel on. Pupil - opening at the center of the iris which controls the amount of light entering the eye.
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Rods & Cones - many more rods (approximately 120 million) than cones (approx 6.4 million). cones - visual receptor cells that are important in daylight vision and color vision. the cones work well in daylight, but not in dim lighting. This is why it is more difficult to see colors in low light. most are located in the center of the retina...called the FOVEA, which is a tiny spot in the center of the retina that contains ONLY cones...visual acuity is best here. rods - visual receptor cells that are important for night vision and peripheral vision. the rods are better for night vision because they are much more sensitive than cones.
Are these triangles real? They appear to be, because the brain automatically fills in lines that are missing. But if you block out parts of the picture, the white triangle vanishes.
The black line in the back seems much longer than the one in the front because your brain assumes it is seeing the effects of perspective. When the background is removed, the lines are seen to be equal.
Seeing In Color
Color Vision Theories: 1.
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Trichromatic Theory this theory indicates that we can receive 3 types of colors (red, green, and blue) and that the cones vary the ratio of neural activity (Like a projection T.V.). The ratio of each color to the other then determines the exact color that we see. Opponent-Process Theory color perception depends on the reception of pairs of antagonist colors. Each receptor can only work with one color at a time so the opponent color in the pair is blocked out. Pairs = red-green, blue-yellow, black- white (light-dark).
Auditory sense Sounds are formed when objects vibrate, thus, the sound waves set-up by these vibrating bodies are transmitted through the air to the ear drum.
Process of hearing: 1.
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Outer Ear The concha/pinna is the external ear part that assembles the sound vibrations to the auditory canal/ meatus to the eardrum. Middle Ear The ear drum vibrates and transmits sound waves to the three small bones Hammer(malleus) Anvil(incus) Stirrups(stapes) Inner Ear 2 structures: Sem-circular canal Cochlea which contains the sensitive structure of hearing.
Auditory Phenomena: Dimensions of tone: 2. Pitch – depends on the number of vibrations per second. 4.
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Loudness – correlated with the amplitude of sound waves - the degree of displacement of the vibrations from its source. Timbre – tonal quality of sound and the complexity of vibrations. Noise Musical harmony Resonance – occurs when another object vibrates as the result of regular impulses sent out by another vibrating body. Masking – interference of one sensory stimulus by another.
Theories of Hearing 1.
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Place Theory of pitch – each part of the basilar membrane is so attuned that it responds only to one frequency. Valley Theory – suggests that the frequency of stimulus may be represented by fibers in the auditory nerve responding independently that the frequency is represented by the composite valley. Frequency Theory – assumes that neural impulses arising in the organ of corti are activated by the basilar membrane of vibration rather than the source. Travelling Wave Theory – when a sound of a given frequency enters the ear, a wave travels along the basilar membrane and displaces it at a maximum amount at a certain point.
Olfaction (Odor sense) Gaseous particles which the nose smells in order to be perceived. Smell has more direct route to the brain.
Phenomena of Olfaction
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The stronger the sensation of odor, the more it somes in contact with the organ of smell. Olfactory Adaptation – occurs after being subjected to the same kind of odor for a specific time. Impaired Olfactory Sensitivity – This is the effects of smoking, colds, etc. blocking the odor which comes incontact with epithelial cells.
Theories of Olfaction 1.
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Traditional theory – odorous substances give off gaseouos particles which stimulates the nose. Radiation Theory – states that the Olfactory Receptors radiate a variety of wave-length bands and that different vapors, when entering the nostrils, absorb different bands.
Gustation (Taste Qualities)
Stimuli of taste are soluble substances in the saliva. Composed of 4 known taste qualities which are: 3. Sweet 4. Salty 5. Sour 6. bitter
The Tongue
Circumvallate Papillae – for bitter taste (back of the tounge)
Fungiform Papillae – sour ans sweet (sides and tips)
Gustatory Phenomena
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The sense of taste is further complicated by the fact that one taste may counteract by the other. Doesn’t only involve the sense of taste but also sensations like pressure, warmth, cold, pain, and odors. Gustatory sense is usually affected by the other senses. Sensations of the taste buds are carried to the central nervous system by 3 cranial nerves: Facial Glosso-Pharyngeal Vagus nerves
Somesthesia (skin sense)
4 different skin senses 2. Pressure 3. Touch 4. Temperature 5. Pain These senses differ from the sensitivity of stimulation within certain areas of the body/skin.
Relative Frequencies of Skin sense in descending order: 1.
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Pain – the immediate stimulus of pain is injury to tissues. Pressure – greatly varies for different parts of the body. - caused by the deforming/bending of the skin.
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Cold – temperature ranges from 10 to 30C
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35 to 70C
Phenomenon of Somesthesia:
Adaptation to pressure is rapid while pain is rather slow.
Perception Perception can be defined as the active process of selecting, organizing, and interpreting the information brought to the brain by the senses.
Gestalt Principles of Perceptual Organization 1.
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figure-ground - this is the fundamental way we organize visual perceptions. When we look at an object, we see that object (figure) and the background (ground) on which it sits. simplicity/pragnanz (good form) - we group elements that make a good form. However, the idea of "good form" is a little vague and subjective. Most psychologists think good form is what ever is easiest or most simple.
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proximity - nearness=belongingness. Objects that are close to each other in physical space are often perceived as belonging together. similarity - As you probably guessed, this one states that objects that are similar are perceived as going together. continuity - we follow whatever direction we are led. common fate - elements that move together tend to be grouped together. closure - we tend to complete a form when it has gaps.
Illusions an incorrect perception caused by a distortion of visual sensations.
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Reversible Figures - ambiguous sensory information that creates more than 1 good form.
The shaded circles seem to form an X made of spheres. But if you rotate the image 180°, the same circles form an X made of cavities, since the brain assumes that light comes from above.
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Impossible Figures objects that can be represented in 2dimensional pictures but can not exist in 3dimensional space despite our perceptions.
THE PERCEPTION OF PAIN Pain is an unpleasant yet important function for survival: warning system (but not all pain is needed for survival).
There are two different pathways to the brain on which pain can travel: 2.
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fast pathways - registers localized pain (usually sharp pain) and sends the information to the cortex in a fraction of a second. EX. - cut your finger with a knife.
slow pathways - sends information through the limbic system which takes about 1-2 seconds longer than directly to the cortex (longer lasting, aching/burning).
Factors in Pain Perception 1.
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expectations - research shown that our expectations about how much something will hurt can effect our perception. Melzack - indicated that believing that something will be very painful helps us prepare for it. personality - people with negative types of personalities often have more pain. mood - bad moods, angry, unhappy, etc, can lead to the experience of increased pain. So, it seems that our brains can regulate, control, determine, and even produce pain.
THEORIES OF PAIN PERCEPTION 1.
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Gate Control Theory (Melzack & Walls, 1965) - incoming pain must pass through a "gate" located in the spinal cord which determines what information about pain will be sent to the brain. So, it can be opened to allow pain through or closed to prevent pain from being perceived. The Gate - actually a neural network controlled by the brain. Located in an area of the spinal cord called the Substansia Gelatinosa. There are two types of nerve fibers in this area: large - sends fast signals and can prevent pain by closing the gate. small - sends slower signals which open the gate. So - when pain occurs it is because the large fibers are off and the small are on, opening the gate. Since the gate is controlled by the brain, he factors discussed earlier (expectations, mood, personality) influence the functioning of the gate.