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

1. Linear Perspective- cue in which 2 parallel lines extend into the distance
2. 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
3. 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
4. Aerial Perspective- haziness that surrounds objects that are farther away from the viewer, causing the distance to be perceived as greater
5. Texture Gradient- tendency for textured surfaces to become smaller and finer as distance from the viewer increases
6. Motion Parallax- close objects move by more quickly than objects farther away
7. 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

1. 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
2. Binocular Disparity- the difference in images between the two eyes, which is greater for objects that are close and smaller for distant objects