Sensation & Perception Ch. 3

Sensation- the process that occurs when special receptors in the sense organs are activated, allowing various forms of outside stimuli to become neural signals in the brain
Transduction- the process of converting outside stimuli, such as light, into neural activity
Sensory Receptors- neurons that transduce physical energy into neural impulses
Sense Organs: eyes, ears, nose, skin, taste buds
Just Noticeable Difference- smallest amt of diff between a standard stimulus intensity and another stimulus; detectable 50% of the time
Absolute Threshold- lowest stim intensity required for detection; 50% of the time

Habituation & Sensory Adaptation

Habituation- brain tendency to stop attending to constant stimulation
Sense Adaptations- sensory receptors become less responsive to repeated presentations of the same stimulus
Signal Detection Theory- provides a method for assessing the accuracy of judgements or decisions under uncertain conditions; used in perception research and other areas. An individual’s correct “hits” and rejections are compared against their “misses” and “false alarms”
Microsaccades- tiny constant, unconscious, eye movements; prevents sensory adapt to visual stimuli

Psychological Aspects to Light

Brightness- determined by wave amp of the wave-higher=brighter, lower=dimmer
Color (Hue)- determined by wave length
Saturation- color purity; mixing black or gray
Visual Accommodations- the change in the thickness of the lens as the eye focuses on objects that are far away or close

Structures of the Eye

Cornea- focuses light
Aqueous Humor- clear fluid nourishes eye
Pupil- the hole light courses through
Lens- finishes focusing process
Visual Accommodation- change in len’s thickness as focuses on objects
Vitreous Humor- jelly-like fluid
Retina- eye component that contains the visual receptors. 3 layers of neurons: ganglion, bipolar, and photoreceptors-visual sense receptors that respond to various light waves
Rods- concentrated at ends of retina; non-color sensitivity to low levels of light, night and peripheral vision
Cones- concentrated at center of retina; color, day, and sharpness vision
Blind Spot- area in the retina where axons of the retinal ganglion cells exit the eye to form the optic nerve; insensitive to light

How the Eyes Work

Dark Adaptation- recovery of sensitivity to stimuli in darkness after exposure to bright lights
Light Adaptation- recovery of sensitivity to stimuli in light exposure to darkness

Color Vision

Trichromatic Theory- proposes three types of cones: red, blue, and green; based on relative firing rates of the three cones, does not acc for non-color, color blindness, after-images
Opponent-Process Theory- proposes 4 primary colors with cones arranged in competing pairs: red/green, blue/yellow, black/white (location- lateral geniculate thalamus)
Monochrome Colorblindness- absence of or dysfunctioning cones
Red/Green Colorblindness- not working

Sound

Wavelength- interpreted as frequency or pitch (high, medium, and low)
Amplitude- interpreted as volume (soft or loud)
Purity- timbre (richness in tone)
Hertz- cycles of waves per second; a measurement of movement of frequency

Structure of the Ear

Auditory Canal- tunnel from pinna to eardrum
Eardrum- vibrates when struck by sound waves; causes 3 bones to vibrate (hammer, anvil, stirrup)
Cochlea- snail-shaped structure of inner ear that is filled with fluid; includes basilar membrane
Organ of Corti- contains receptor hair cells for sense of hearing
Hair Cells- auditory receptors where sound waves become neural impulses
Auditory Nerve- bundle of axons from hair cells in the inner ear
Pitch- corresponds to sound waves frequency; high frequencies=higher pitches
Place Theory- different pitches based on stimulations of hair cells in different locations on the organ of corti

Theories of Pitch

Frequency Theory- pitch is related to vibration speed in basilar membrane (100 Hz and lower)
Volley Principle- frequencies above 100 Hz cause hair cells (auditory neurons) fire in a volley pattern (taking turns firing)

Taste

Taste Buds- taste receptor cells in mouth
Gustation- sense of taste
5 Basic Tastes: sweet, sour, salty, bitter, brothy (umami)

Smell

Olfaction- sense of smell
Olfactory Bulbs- brain areas receive information from olfactory receptor cells (1,000+)

Somesthetic Senses

Proprioception- awareness of where the body and body parts are located in relation to each other in space and to the ground
Somesthetic Senses- the body senses consisting of the skin senses, the kinesthetic sense, and the vestibular senses
Gate-Control Theory- pain signals must pass through a “gate” in the spinal cord
Kinesthetic Sense- senses the position and movement of the body we are aware of only on introspection
Vestibular Senses- the awareness of the balance, position, and movement of the head and body through space in relation to gravity’s pull

Perception and Constancies

Perception- experiences at any given moment are interpreted and organized in some meaningful fashion
Size Constancy- same size regardless of distance
Shape Constancy- interpreting shape being constant regardless when its shape changes on the retina
Brightness Constancy- perceiving brightness of objects as the same even when the light conditions change

Gestalt Principles

Figure-Ground- tendency to perceive objects or figures as existing on a background
Reversable figures- visual illusions in which the figure and ground can be reversed

Gestalt Principles of Grouping

Similarity- the tendency to perceive objects that look similar to each other as being part of the same group
Proximity- the tendency to perceive objects close to each other as being part of the same grouping; physical or geographical nearness
Closure- tendency to complete figures that are incomplete
Continuity- the tendency to perceive things as simply as possible with a continuous pattern rather than with a complex, broken-up pattern
Contiguity- the tendency to perceive 2 things that happen close together in time as being related

Development of Perception

Depth Perception- the ability to perceive the world in three dimensions
Perceptual Set (Expectancy)- the tendency to perceive things a certain way because of previous experiences or expectations influence those perceptions
Top-Down Processing- the use of preexisting knowledge to organize individual features into a unified whole
Bottom-Up Processing- the analysis of the smaller features to build up to a complete perception

Monocular Cues

Monocular Cues (Pictorial Depth Cues)- perceiving depth with one eye only
Binocular Cues- cues for perceiving depth based on both eyes

Linear Perspective- cue in which 2 parallel lines extend into the distance
Relative Size- monocular depth perception cue; perception that occurs when objects that a person expects to be of a certain size appear to be small, and are, therefore, assumed to be much farther away
Interposition- the assumption that an object that appears to be blocking part of another object is in front of the second object and closer to the viewer
Aerial Perspective- haziness that surrounds objects that are farther away from the viewer, causing the distance to be perceived as greater
Texture Gradient- tendency for textured surfaces to become smaller and finer as distance from the viewer increases
Motion Parallax- close objects move by more quickly than objects farther away
Accommodation- the brain’s use of information about the changing thickness of the lens of the eye in response to looking at objects that are close or far away

Binocular Cues

Convergence- rotation of eyes in their sockets to focus on a single object; resulting in greater convergence for closer objects and lesser convergence if objects are distant
Binocular Disparity- the difference in images between the two eyes, which is greater for objects that are close and smaller for distant objects