Understanding Sensation, Perception, and Sensory Processes
Sensation: The process by which sensory receptors capture, transduce, and transmit information to the brain.
Attention: The process by which individuals select certain stimuli.
Perception: The cognitive process by which individuals shape sensitive information into meaningful objects.
The Basic Processes:
- Receptor Cells: Specialized cells that respond to a particular type of energy (e.g., auditory, touch, smell, taste).
- Doctrines of Specific Nerve Energies: A one-to-one relationship between the stimulation of specific nerves and sensory outcomes.
Sensory Thresholds:
- Absolute Threshold: The minimum intensity of a stimulus that must be present for it to be detected.
Extrasensory Perception: This refers to extraordinary perception, including:
- Clairvoyance: Awareness of an event or unknown object.
- Telepathy: Knowledge of the thoughts or feelings of someone else.
Visual System:
- Cornea: The transparent membrane covering and protecting the front of the eye.
- Pupil: A small opening in the iris through which light enters.
- Iris: The colored part of the eye that contracts or relaxes.
- Lens: The transparent part of the eye within the pupil that focuses light (proximity/roundness, remoteness/flattens).
- Retina: The coating of the eye that contains receptor cells sensitive to light.
- Fovea: The area where central visual field images are focused most sharply.
Receiver Cells:
Cells in the retina that are sensitive to light. Visual receptors include rods and cones.
Receptor Cells:
- Bipolar Cells: Relay relevant information from the receptor cells.
- Ganglion Cells: Receive information from the bipolar cells (axons form the optic nerve).
Adaptation:
- Dark Adaptation: Increases the sensitivity of rods and cones in low light.
- Light Adaptation: Decreases the sensitivity of rods and cones in bright light.
Brain-Eye Connection:
- Optic Nerve: A bundle of ganglion cell axons that carry nerve messages from each eye to the brain.
- Optic Chiasm: The point near the base of the brain where some fibers of the optic nerve from each eye cross to the other side of the brain.
Hearing: The interpretation that our brain makes of the ebb and flow of air molecules hitting our eardrum.
Sound:
- Sound Waves: Changes in pressure caused when air or liquid molecules collide and then depart.
- Frequency: The number of waves measured in cycles per second, expressed in Hertz (Hz). Frequency determines pitch.
- Amplitude: The magnitude (height) of a sound wave that determines volume, measured in decibels (dB).
- Overtones: Tones resulting from sound waves that are multiples of the basic tone.
- Timbre: The quality or texture of sound, caused by overtones.
Hearing Mechanism:
- Eardrum: Sound waves strike it.
- Middle Ear: Contains three tiny bones: the hammer, anvil, and stirrup, which transmit vibrations to the inner ear.
- Basilar Membrane: A diaphragm in the cochlea containing receptor cells, including hair cells (in the organ of Corti).
- Auditory Nerve: Connects the ear to the brain, providing information to both sides of the brain.
Theories of Hearing:
- Place Theory: The brain determines pitch based on the location of stimulation on the basilar membrane.
- Frequency Theory: The frequency of hair cell discharge in the cochlea determines pitch.
- Temporal Theory: The overall pattern of discharge corresponds to the frequency of the sound wave.
Smell: The detection of common odors is triggered by olfactory binding proteins (OBPs), which bind with molecules transported by air. These molecules activate receptors in the olfactory epithelium, and the axons project directly to the olfactory bulb. Women generally have a better sense of smell than men.
Anosmia: The complete loss of the ability to smell.
Taste: The receptor cells are located in taste buds, which are housed in the papillae of the tongue. The chemicals in the foods we eat are dissolved in saliva and come into contact with taste receptors.
Laws of Perception:
- Bottom-Figure Principle: The mind “knows” when a stimulus is organized in a way that stands out against a background.
- Similarity: When there are several elements of different classes, there is a tendency to group those that are similar.
Nearness: When parts of a whole receive the same stimulus, they coalesce into groups based on minimal distance.
Pregnancia, Fitness, or Simplicity: The tendency to perceive stimuli as regular, simple, symmetrical, orderly, and understandable, which aids in memorization.