Chapter 4: Sensation and Perception 4.1-4.3 (Visual) Flashcards
Sensation
simple stimulation of a sense organ; basic registration of light, sound, pressure, odor, taste as parts of your body interact with the physical world
Perception
organization, identification, and interpretation of a sensation in order to form a mental representation
Transduction
sense receptors convert physical signals from the environment into neural signals that are sent to the CNS
Sensory adaptation
sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current (unchanging) conditions
Psychophysics
methods that systematically relate the physical characteristics of a stimulus to an observer’s perception
Absolute threshold
minimal intensity needed to just barely detect a stimulus in 50% of the trials
Sensitivity
how responsive we are to faint stimuli
Acuity
how well we can distinguish two very similar stimuli
Just noticeable difference (JND)
minimal change in a stimulus that can just barely be detected
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)
way of analyzing data from psychophysics experiments that measure an individual’s perceptual sensitivity while taking noise, expectations, motivations, and goals into account
Decision criterion of SDT
(1) strength of the sensory evidence for that stimulus (2) the amount of evidence necessary for your perceptual system to “decide” that the stimulus is present
Visual acuity
ability to see fine detail
Properties of light waves
Length (hue or what we perceive as color), amplitude (brightness), purity (saturation or richness of color)
Accommodation
process by which the eye maintains a clear image on the retina
Two types of photoreceptor cells in the retina
Contain light-sensitive proteins that absorb light and transduce it into electrical signals: Cones (color, fine detail, normal daylight) and Rods (night vision, low-light)
Fovea
an area of the retina where vision is clearest and there are no rods
Blind spot
location in the visual field that produces no sensation on the retina
Layers of the retina
photoreceptor cells beneath a layer of transparent neurons called bipolar and retinal ganglion cells
Bipolar cells
collect electrical signals from rods and cones and transmit them to the outermost layer of the retina
Retinal ganglion cells (RGCs)
they organize the signal from bipolar cells and send them to the brain
Lateral geniculate nucleus (LGN)
located in the thalamus of each hemisphere, from where visual signals travel to area V1 at back of the brain
Area V1
part of the occipital lobe that contains the primary visual cortex
Visible spectrum
rainbow of hues and accompanying wavelengths
Types of cones
Sensitive to red (long wavelengths), green (medium wavelengths), blue (short wavelengths) light
Color vision deficiency or color blindness
Genetic and sex-linked disorder in which one, two, or all three cone types are missing
Color-opponent system
pairs of cone types (channels) work in opposition: L-cone against M-cone, S-cone against M-cone; explains color afterimage
Visual receptive field
region of the visual field to which each neuron responds
Two visual streams or pathways
Ventral (lower) stream and dorsal (upper) stream; functionally distinct
Ventral stream, the “what” pathway
travels across occipital lobe into lower levels of the temporal lobes and includes brain areas that represent an object’s shape and identity
Dorsal stream, the “perception for action” pathway
travels up from the occipital lobe to the parietal lobes (including some middle and upper levels of temporal lobes) and includes brain areas that identify where an object is and how it’s moving
Binding problem
how the brain links features together so that we see unified objects in our visual world rather than free-floating or miscombined features
Parallel processing
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 e.g. color and shape
Feature-integration theory
focused attention is not required to detect the individual features that make up a stimulus but it is required to bind those features together
Attention
active and conscious processing of particular information
Perceptual constancy
as aspects of sensory signals change, perception remains constant
Perceptual contrast
although sensory information from two things may be very similar, we perceive the objects as different
Perceptual organization
process of grouping and segregating features to create whole objects organized in meaningful ways
Gestalt principles of perceptual grouping
Simplicity, closure, continuity, similarity, proximity, common fate
Dimensions in the retinal image
Length and width
Monocular depth cues
aspects of a scene that yield information about depth when viewed with only one eye
Binocular depth cues (binocular disparity)
the difference in retinal images of the two eyes to provide information about depth; farther object mapped in similar location in the retina
Apparent motion
perception of movement as a result of alternating signals appearing in rapid succession in different locations
Spacial acuity
ability to distinguish two features that are very close together in space
Temporal acuity
ability to distinguish two features that are very close together in time
Change blindness
when people fail to detect changes to the visual details of a scene
Inattentional blindness
failure to perceive objects that are not the focus of attention
Filling-in
our perceptual system uses visual information around the blind spot to fill in area occupied by it
Synesthesia
Coupling of two or more senses in around 4% of population
Additive color mixing (lights)
Mixing different amounts of visible light waves (primarily red, blue, and green) becomes closer to white as more is added
Subtractive color mixing (paints)
Absorbing/subtracting some light wavelengths and reflecting others (primarily cyan, magenta, and yellow) until it becomes black (all absorbed, none reflected)
Types of monocular depth cues
linear perspective, texture gradient, interposition, relative size, familiar size, relative height
Binocular rivalry
two dissimilar images are presented simultaneously to each eye and perception alternates
3D anaglyph images
creating depth perception using binocular disparity
Visual-form agnosia
impairment in recognition of visual objects due to damage in lateral occipital cortex (ventral)
Mcgurk effect
effect in which conflicting visual and auditory components of a speech stimulus result in illusory percept
