Sensation & Perception

SENSES - Sensation is the stimulation of the sense organs & perception is the selection, organization and interpretation of sensory input.
1. psychophysics – the study of how physical stimuli are translated into psychological experience.
  1. The gustatory receptors are taste buds that line the trenches around tiny bumps on the tongue called papillae. Physical stimuli are chemical senses dissolved in the mucous in the nose. Receptors for smell are called olfactory cilia, hair in the nasal.
2. Sensory adaptation is the gradual decline in sensitivity to prolonged stimulation.
3. Properties of sound - 1. Wavelength or frequency – pitch., measured in Hertz (Hz). Humans only hear from 20 – 20,000 Hz, but usually 2000-4000 Hz. 2. Wave amplitude – corresponds to the psychological quality of loudness. It is measured in decibels (dB) After 120 dB it is painful. 3. Wave purity or mixture – timbre or complexity of the sound wave.
4. SENSE OF TOUCH - Nerve fibres that carry incoming messages from the outside world go to the spinal cord and then the brain stem where they cross to the opposite side of the brain. Tactile signals then pass through the thalamus to the somatosensory cortex in the parietal lobe.
  1. Pain - The fast pathway uses myelinated neurons and registers localized pain in a fraction of a second. The slow pathway uses unmyelinated neurons and lets us know about less localized, longer lasting aches and burning pain that comes later.
Absolute threshold - Is for a specific type of sensory input which is the minimum of stimulation that an organism can detect
JND - Fechner’s law states that the amount of your sensory experience is proportional to the number of JND’s that the stimulus is above absolute threshold. Weber found that the size of a JND is a constant proportion of the size of the initial stimulus and is known as Weber’s fraction.
THE EYE - The pupil constricts in bright light and dilates in dim light. The lens is structured with muscles attached to it that focuses on the light. The retina is the neural tissue lining the inside back surface of the eye; it absorbs light. Cones are specialized visual receptors that play role in daylight vision and colour vision. Rods are specialized visual receptors that play role in night vision and peripheral vision and are sensitive to dim light.
1. Signals to the brain - The optic nerve is a collection of axons that connect the eye with the brain.
2. Theories - Hermann von Helmholtz, stated that the human eye has three types of receptors with differing sensitivities to different light wavelengths, specifically, red, blue, and green. Ewald Hering proposed the opponent process theory that colour perception depends on receptors that make opposite responses to three pairs of colours: blue/yellow, red/green, and black/white.
Processing - Botom-up processing – used in feature analysis. Start at parts and build toward the whole. Top-down processing – brain uses this also like reversible figures or when we perceive a word before we know all the individual letters.
THE EAR - There are 3 parts 1. Outer ear – sound is conducted by vibration of air molecules. The main part is the Pinna. 2. Middle ear - sound is conducted by vibration of movable bones (smallest bones in body) called the hammer, anvil, and stirrup, known together as the ossicles. . Inner ear – sound is conducted by waves in a fluid which are then converted into neural signals and sent to the brain.

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Sensation & Perception

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	Created by heavenstaar about 9 years ago