Developmental psychology.pdf

144 Modes of Awareness
5. The stimuli for hearing are sound waves entering the outer ear, making the
eardrum vibrate. This vibration is carried through the middle ear and into
the cochlea of the inner ear, where a liquid is set in motion, causing the
bending of small hair cells. The movement of these cells arouses nerve
impulses that travel over the auditory nerve to the brain. According to the
place theory of hearing, certain regions of hair cells are especially attuned
to certain vibration frequencies. According to the volley theory, nerve fibers
operate in groups, and the experience of pitch depends upon the frequency
of volleys rather than the frequency of vibration within any individual fiber.
6. Smell plays a subtle role in everyday life, especially in its contribution to
what is usually considered to be taste. The olfactory receptors are located
high in the nostrils and are stimulated only by odorous substances.
7. Gustatory sensitivity at the human level consists of four primary qualities:
salty, sour, sweet, and bitter. The receptors are small cells located in buds
within the walls of the papillae of the tongue. Substances must be soluble to
stimulate them, but olfactory and cutaneous cues are also important in
taste.
8. The primary skin senses, once referred to as the sense of touch, are
pressure, pain, and temperature. Cutaneous sensitivity to light pressure is
mediated by hair follicles and other mechanisms; heavy pressure is perhaps
mediated by the Pacinian corpuscles; and pain sensitivity is mediated by
free nerve endings. No specialized receptors have been identified for
warmth or cold.
Proprioceptive Senses
9. Kinesthetic sensitivity results from activation of receptors in the muscles,
tendons, and joints. Muscular activities and posture therefore provide their
own feedback, which underlies the automaticity of well-established motor
responses.
10. Our sense of balance or equilibrium, such as being right side up or upside
down, is based on activities in the nonauditory labyrinth of the inner ear.
Hair cells in two small chambers, collectively known as the vestibular
system, provide this information.
11. Awareness of linear motion, which is passive motion in a straight line, also
arises through events in the vestibular system, and the only adequate
stimulus is a change in rate of movement. Sensitivity to rotary motion
comes from another part of the nonauditory labyrinth. Hair cells in the
semicircular canals are stimulated to bend one way or the other,
transmitting impulses to the brain. Again, a change in motion is the
adequate stimulus. Vision, kinesthesis, and other sensory systems also
contribute to our sense of passive motion.
Sensation and Perception
12. Awareness usually involves intersensory or multisensory perception. Our
information about the world at any given moment is based on several sense
organs and also upon data previously stored in the brain. The various
sensory systems operate in an interrelated and active manner.
13. Extrasensory perception implies perception without the involvement of any
currently known sense organs. This alleged phenomenon has been
questioned chiefly on the basis of unreliable evidence, problems of
dishonesty, and inadequate research methods.