Chapter 3 Psych 1 Online Stud 1199408234400754 3[1]

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4th Edition

Sensation and Perception

Chapter 3

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Sensation, Perception and Psychophysics

• Vision

• Hearing

• Taste

• Smell

• Body position

• Movement

We receive and process information about:

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Sensation, Perception and Psychophysics

• Sensation refers to stimulation or activation of the receptors.

• Perception is the organization of what you have sensed.

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Sensation, Perception and Psychophysics

• Receptors for each sensory system respond to only one type of environmental stimulus.

• Transduction – physical properties are converted to a form we can perceive.

• Adaptation occurs when continued presentation of the same stimulus results in a loss of sensitivity.

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Sensation, Perception and Psychophysics

• Psychophysicists, such as Ernst Weber and Gustav Fechner, studied the relationship between the mind and the body.

• Weber: Just noticeable difference (jnd) – The smallest amount of energy that must be added or subtracted to detect change 50% of the time

• Absolute Threshold

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Sensory SystemsVision

• Light waves differ in terms of wavelength (hue) or color, anplitude (intensity), and saturation (purity).

• The psychological counterpart of wavelength is color.

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Sensory SystemsVision

• Saturation = “trueness” of only one hue.

• Amplitude = intensity.

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Additive and Subtractive Processes of Color Mixing

• Radiant light is visible energy emitted by an object• Reflected light is light waves that are reflected from

objects

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Sensory SystemsVision

• Sensory systems of the eye consists of Rods and Cones. –The cones have greater acuity, respond to color, and have a higher threshold for activation.About 120 million per eye.

–The rods have lower acuity, respond to black and white and shades of gray, and have a lower threshold.About 7 million per eye.

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Sensory SystemsVision

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Sensory Systems

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Sensory SystemsVisual Pathways

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Two theories of color vision

• The trichromatic theory proposes that there are three different types of cones;

• The opponent-process theory argues that color-sensitive cells are arranged in pairs.

• Both theories are supported by research findings.

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Opponent-process Theory

Pairs of Yellow-Blue and Red-Green Cones

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Color Blindness

• Dichromats lack the ability to see one of the three primary colors.

• Monochromats are unable to see color.

IshiharaPlate

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Sensory SystemsAudition

• Audition is initiated by the movement of molecules in the air.

• Varies by wavelength (frequency), amplitude (intensity), and purity (timbre)

• Vibration of the eardrum starts a chain reaction that results in movement of fluid in the inner ear and the bending of specialized hair cells, which are the receptors for hearing.

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Sensory Systems

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Hearing Disorders

Conduction deafness

Sensorineural deafness

Central deafness

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Sensory SystemsGustation

• Molecules in solution stimulate taste.

• Hairs on taste buds, serve as the receptors.

• Each receptors may respond to several tastes, but each one is maximally sensitive to one of four tastes salty, sweet, sour, or bitter. Some people add metallic and alkaline

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Gustation

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Sensory Systems

• Molecules in the air stimulate the sense of smell.

• Hairs located in the nasal cavity serve as the receptors.

• Olfaction has a direct connection to the limbic system [next]

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Sensory Systems Vestibular Sense

• The vestibular sense enables us to adjust to different bodily movements.

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Sensory Systems Kinesthetic Sense

• The kinesthetic sense allows us to determine the position of our extremities.

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Sensory SystemsCutaneous Senses

• Mechanoreceptors• Nocioreceptors• Thermoreceptors

Cutaneous receptors for pressure, pain, and temperature are located in the skin.

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Perception

• We engage in selective attention because we cannot process all of the stimuli we encounter.

• Dichotic listening experiments study divided attention.

• With practice we can learn how to divide our attention effectively.

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PerceptionSize Constancy

• We experience perceptual constancies when our perception of an object does not change, even though the retinal image.

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Shape Constancy

Perception of shape remains constant even though image on retina changes.

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Depth Perception and Binocular Disparity

Close objects translate very fast (brush) and distant objects pass very slow (mountains).

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Gestalt Principles of Perception

• We actively organize our perceptual world into meaningful groups or wholes.

• The figure-ground relation is one of the most basic perceptual organizations.

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Gestalt Principles of Perception

Proximity

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Perception

• Perceptual hypotheses are inferences about the nature of the stimuli we sense.

• Perceptual illusions and ambiguous figures may cause us to develop incorrect perceptual hypotheses.

• Hermann grid

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Ames Room

In the Ames Room, even the size of a familiar object (such as a person) is perceived largely distorted, because the misleading geometry generates an incorrect frame of reference

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Zener Cards

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Skeptics

Zener Cards, ESP, Telekinesis