Chapter 4: Sensation & Perception Flashcards
Sensation
Simple stimulation of a sense organ; basic registration of sound, light, pressure, odor, taste, etc.
Perception
Occurs in the brain as sensation is registered there; characterized by organization, identification, interpretation, and a general mental representation of the sensation
Transduction
When sense receptors convert physical signals from the environment into neural signals that are sent to the CNS.
Each sensory organ can only transduce physical signals into their specific type of neural signals, which is why rubbing your eyes is perceived as color
Sensory adaptation
Sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current unchanging conditions
Multisensory
An event that stimulates multiple senses at the same time
Psychophysics
Methods that systematically relate the physical characteristics of a stimulus to an observer’s perception
Absolute threshold
The minimal intensity needed to just barely detect a stimulus in 50% of trials; related to sensitivity and acuity
Psychometric function
The graph that shows the absolute threshold for a stimulus
Sensitivity
How responsive we are to faint stimuli
Acuity
How well we can distinguish between two very similar stimuli
Just noticeable difference (JND)
The minimal change in a stimulus that can just barely be detected; depends on the sense being measured and the intensity of the original stimulus (Standard (S))
Weber’s Law
For every sense domain, the change in a stimulus that is just noticeable is a constant ratio of the standard stimulus, over a range of standard intensities
Signal Detection Theory (SDT)
A way of analyzing data from psychophysics experiments that measures an individual’s perceptual sensitivity while also taking noise, expectations, motivations, and goals into account
Perceptual sensitivity
How effectively the perceptual system represents sensory events
What two factors impact whether or not a stimulus is perceived?
1) The strength of the sensory evidence for that stimulus
2) The decision criterion
Decision criterion
The amount of evidence necessary for the perceptual system to “decide” that the stimulus is present; liberal criterion and conservative criterion
Hit
Stimulus is present and detected
Miss
Stimulus is present and not detected
False alarm
Sensory is not present but is detected
Correct rejection
Stimulus is not present and is not detected
Liberal criterion
Not much sensory evidence is required
Conservative criterion
Stronger sensory evidence is required
Visual acuity
Ability to see fine details; receptors in eyes respond to wave lengths of light energy; spatial acuity and temporal acuity
Spatial acuity
Ability to distinguish between two features close together in space
Temporal acuity
Ability to distinguish between two features close together in time
The three physical properties of light waves
Length, amplitude, purity
Light wave length
Distance between the crests of the waves; impacts hue/color
Light wave amplitude
Distance between the crest and trough; impacts brightness
Light wave purity
Saturated vs. desaturated; impacts richness of color
Front of eye functions
Focuses and controls amounts of light entering eye
Retina location and function
Inner surface of eye where light is transduced
Accommodation
The process by which the eye maintains a clear image on the retina; ciliary muscles adjust the thickness of the lens
Myopia
Nearsightedness; accommodation is shifted closer
Hyperopia
Farsightedness; accommodation is shifted farther away
Photoreceptors
Rods and cones
Rods
- respond to dim illumination and shapes
- active only under low-light conditions
- about 120 million per eye
- located on the periphery of the retina
Cones
- detect color (red, green, blue)
- operate under daylight conditions
- detect fine detail
- about 6 million per eye
- primarily in the fovea
Fovea
Small region of densely packed cones at the center of the retina; no rods so vision is clearest here
Blind spot
A location in the visual field that produces no sensation on the retina
Area V1
The part of the occipital lobe that contains the primary visual cortex
Color
Our perception of light wavelengths on the visible spectrum
Trichromatic color representation
The pattern of responding across the three types of cones that provides a unique code for each color: long cones are red, medium cones are green, short cones are blue
Opponent Process Theory
Problem with cones that means that all color experiences arise from three systems with two opponent elements:
- red-green
- blue-yellow
- black-white
Stimulation of one color of a pair will inhibit the other
Three types of cone problems
- Color deficiency/blindness
- Color-opponent system (Opponent Process Theory)
- Color afterimage
Visual receptive field
The region of the visual field to which each neuron responds; V1 has a small receptive field, meaning that it only responds to small parts of the visual field
Area A1
The primary auditory cortex in the temporal lobe
Hearing
The detection of sound waves or changes in air pressure unfolding over time
The three physical properties of sound waves
Frequency, amplitude, timbre/complexity
Sound wave frequency
The distance between crests of each wave; our perception of pitch:
- low frequency means low pitch
- high frequency means high pitch
Sound wave amplitude
The height measured between each crest and trough; our perception of volume:
- high amplitude is loud
- low amplitude is quiet
Sound wave complexity
How many frequencies are present; our perception of timbre:
- simple, one frequency, pure tone
- complex, mix of frequencies
Three main ear divisions
Outer ear, middle ear, inner ear
Outer ear parts
Pinna, auditory canal, eardrum
Middle ear parts
Ossicles (malleus, incus, stapes)
Inner ear parts
Cochlea, basilar membrane
Two main types of hearing loss
- conductive hearing loss
- sensorineural hearing loss
Conductive hearing loss
Damage to eardrum
Sensorineural hearing loss
Damage to cochlea, hair cells, or auditory nerve
Cochlear implant
Electronic device that replaces the function of hair cells
The two chemical sense
- olfaction: smell
- gustation: taste
How are olfaction and gustation connected?
Smell and taste work together to produce flavor; stimuli borne in the air provides smell and is soluble in saliva to provide taste
How does sense of smell work?
Odorant molecules travel through the nose to the olfactory epithelium where they bind to olfactory receptor neurons (ORNs) that initiate the sense of smell
Which two approached regulate the connection between sense of smell and emotional/social behavior?
Object-centered approach and valence-centered approach
Object-centered approach
Info about the identity of odor object is quickly accessed from memory, which triggers a emotional response
Valence-centered approach
Emotional response comes first and provides a basis for determining the identity of the odor
Pheromones
Chemicals that may affect sexual behavior
Synesthesia
Linking the stimuli of one sense to another unrelated sense
Ventriloquist Illusion
The phenomena of “believing” our visual system over our auditory system
Visual streams
The two functionally distinct pathways of the visual processing system:
- ventral (lower) stream
- dorsal (upper) stream
Ventral visual stream
Travels across the occipital lobe into the lower levels of the temporal lobes; these brain areas represent the object’s shape and identity, therefore it is also called the “what” pathway
Dorsal visual stream
Travels up from the occipital lobe to the parietal lobes; these brain areas identify where an object is and how it’s moving, but is also crucial for guiding actions such as aiming and reaching, therefore called “where” pathway or “perception for action” pathway
Binding problem
How the brain links features together so that we see unified objects in our visual world rather than free-floating or mis-combined features
Parallel processing
The brain’s capacity to perform many activities at the same time
Illusory conjunction
A perceptual mistake whereby the brain incorrectly combines features from multiple objects
Feature-integration theory
The idea that focused attention is not required to detect the individual features that make up a stimulus (color, shape, size, etc.), but it is required to bind those individual features together
Attention
The active and conscious processing of particular information
Perceptual constancy
Even as aspects of sensory signals change, perception remains constant
Perceptual contrast
Although the sensory information from two things may be very similar, we perceive the objects as different
What are the two different components to recognition?
Modular view and conceptual knowledge
Modular view
The idea that specialized brain areas detect and represent faces, houses, body parts, etc.
Conceptual knowledge
The idea that our preexisting knowledge about an object is present when we recognize an object
Perceptual organization
The process of grouping and segregating features to create whole objects organized in meaningful ways; connected to Gestalt psychology
What are the six perceptual grouping rules?
Simplicity, closure, continuity, similarity, proximity, common fate
Simplicity
The visual system selects the simplest or most likely interpretation of an object
Closure
We tend to fill in missing elements of a visual scene in order to perceive separate parts as a whole
Continuity
We tend to group together edges of contours that have the same orientation (this is good continuity)
Similarity
Regions that are similar in color, shape, texture, etc. are seen as belonging to the same object
Proximity
Objects that are close together tend to be grouped
Common fate
Elements of a visual object that move together are seen as parts of a single moving object
Monocular depth cues
Aspects of a scene that yield info about depth when viewed with only one eye
What are the five monocular depth cues?
Relative/familiar size, linear perspective, texture gradient, interposition, relative height
Relative/familiar size
Used to perceive distance when the size of an object is known
Linear perspective
The phenomena where parallel lines seem to converge as they recede
Texture gradient
How textures look more detailed up close and more uniform from far away
Interposition
When one object partially blocks another, we know which one is closer
Relative height
Objects that are close tend to be lower in the visual field, while objects that are farther tend to be higher
Binocular disparity
The difference in the retinal images of the two eyes; this provides depth perception
Apparent motion
Perception of movement as a result of alternating signals appearing in rapid succession in different locations (i.e., digital traffic signs with the arrows)
Change blindness
When people fail to detect changes in the visual details of a scene because the visual world is too rich for us to take everything in
Inattentional blindness
A failure to perceive objects that are not the focus of attention
Cochlea
Fluid-filled tube containing cells that transduce sound vibrations into neural impulses
Basilar membrane
A structure in the inner ear that divides the cochlea length-wise; moves up and down in time with vibrations relayed from the ossicles and transmitted through the oval window
Inner hair cells
Specialized auditory receptor neurons embedded in the basilar membrane and stimulated by moving cochlear fluid
Which two functions help the brain determine pitch?
Place code and temporal code
Place code
The brain uses info about the relative activity of hair cells across the basilar membrane to help determine pitch
Temporal code
The brain uses the timing of action potentials in the auditory nerve to help determine pitch
Haptic perception
Active exploration of the environment by touching and grasping objects with our hands
Tactile receptive field
The small patch of skin to which each receptor is sensitive
Thermoreceptors
Nerve fibers that sense cold and warmth and respond when skin temperature changes
A-delta fibers
Axons that transmit sharp initial pain
C fibers
Axons that transmit long-lasting, dull, persistent pain
Referred pain
When sensory info from internal and external areas converges on the same nerve cells in the spinal cord, causing us to sometimes feel internal pain as external
Gate-Control Theory
Signals arriving from pain receptors in the body can be stopped by interneurons in the spinal cord via feedback from the skin or from your brain
Proprioception
Your sense of body position
Vestibular system
The three fluid-filled semicircular canals and adjacent organs located next to the cochlea in each inner ear; maintains balance along with hair cells
Olfactory bulb
Brain structure located above the nasal cavity and beneath the frontal lobes; axons from ORNs extend to here
Olfactory sensitivity
The ability to detect odors
Olfactory acuity
The ability to discriminate among odors
