4 th Edition Copyright 2004 Prentice Hall3-1 Psychology Stephen F. Davis Emporia State University...

Copyright 2004 Prentice Hall 3-1

4th Edition

PsychologyStephen F. Davis

Emporia State University Joseph J. Palladino

University of Southern IndianaPowerPoint Presentation by H. Lynn Bradman

Metropolitan Community College-Omaha


4th Edition

Sensation and Perception

Chapter 3


Sensation, Perception and Psychophysics

• Sensation refers to stimulation or activation of the receptors.

• Sensations are the basic building blocks of perception, the process of interpreting or making sense of our sensory input.



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

• Transduction is the process by which the receptors change the energy they receive into a form that can be used by the nervous system.

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



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

• Weber’s law relates the amount of change in a stimulus and the conscious experience of change in the stimulus.



• Fechner studied:– The smallest amount of energy that could be

detected 50% of the time (the absolute threshold)

– The smallest change that could be detected 50% of the time (the differential threshold or Just Noticeable Difference (Jnd).


Sensory Systems

• The visual receptors, the rods and cones, respond to a limited range of light waves, the visible spectrum.


Sensory Systems

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


Sensory Systems

• The cones have greater acuity, respond to color, and have a higher threshold for activation.

• The rods have lower acuity, respond to black and white and shades of gray, and have a lower threshold.


Sensory Systems


Sensory Systems

• The visual receptors are located in the retina at the back of the eye.

• To reach the receptors, light waves pass through several other structures in the eye, as well as several layers of retinal cells.


Sensory Systems


Sensory Systems

• Two theories of color vision have been formulated.

• 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.


Sensory Systems

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

• Monochromats are unable to see color.


Sensory Systems

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

• 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.


Sensory Systems


Sensory Systems

• The pitch or frequency of a sound wave is determined by the location of the hairs that are activated (Place theory) and the rapidity with which the basilar membrane vibrates ( theory).


Sensory Systems

• Hearing disorders can result from damage to the bones of the middle ear (conduction deafness), the inner ear, especially the hair cells (sensodneural deafness), or the auditory nerve and auditory cortex (central deafness).


Sensory Systems

• The chemical senses include the sense of taste (gustation) and the sense of smell (olfaction).


Sensory Systems

• Molecules in solution stimulate taste.• Hairs, located on structures known as

taste buds, serve as the receptors.• Although receptors may respond to

several tastes, each one is maximally sensitive to one of four tastes salty, sweet, sour, or bitter.


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; as a result, many of our memories involving odors are highly emotional.


Sensory Systems

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

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

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


Perception

• Perception is the process of organizing and making sense of the stimuli in our environment.

• Our motives help determine which stimuli we perceive.


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.


Perception

• To attract our attention, stimuli should be more colorful, larger, and louder than other stimuli in our environment.


Perception

• The ability to discriminate among shapes and figures is known as pattern perception.

• The feature analysis theory states that we perceive the elements of an object and then combine them to produce our perception of the object (bottom-up processing).

• Other research has shown that we perceive the object before we perceive its elements (top-down processing).


Perception

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


Perception

• The Gestalt psychologists demonstrated that we actively organize our perceptual world into meaningful groups or wholes.

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

• Additional principles for the grouping of stimulus elements are proximity, similarity, good continuation, and closure.


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.


Perception

• Parallel, as opposed to sequential, processing appears to characterize much of our perceptual activity.

• Parallel processing is seen in visual search, in which a target stimulus must be distinguished among a group of distractors.


Perception

• Perception may be influenced by the social context.

• For example, the Ebbinghaus illusion is influenced by the type of social stimuli used.


Paranormal Phenomena

• Extrasensory perception (ESP) refers to the occurrence of experiences or behaviors in the absence of an adequatestimulus.

• Such occurrences are considered to be paranormal, or beyond our normal sensory abilities.

• Clairvoyance, telepathy, precognition, and psychokinesis are examples of paranormal phenomena

4 th Edition Copyright 2004 Prentice Hall3-1 Psychology Stephen F. Davis Emporia State University...

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