Ch. 5: Sense perception pt. I Flashcards
Sensation
The detection of physical stimuli and transmission of that information to the brain
Perception
The brain’s processing, organization, and interpretation of stimuli received through sensation.
Bottom-up processing
based off of sensory input
Top-down processing
Processing sensory input s.t. the interpretation of sensory information is mostly governed by past experiences, expectations, etc., rather than the stimuli’s signals themselves
Transduction
Sensory receptors receive stimulation depending on the sense that they correspond to, and then translate of the physical properties of stimuli into neural impulses sent to the brain.
Quantitative vs. qualitative sensory information
Qualitative is what type of information of a certain sense was detected (ie. sweet vs. sour), while quantitative is how strong it was.
Absolute threshold
The minimum intensity of a stimulus for someone to detect it 50% of the time
Difference threshold and Weber’s law
minimum change in intensity for someone to detect the change. The bigger the stimulus, the bigger the difference must be for someone to notice it, which is Weber’s law.
Signal Detection Theory
This theory says that detection of a stimulus is not an objective process. It is a subjective decision dependent on: sensitivity to the stimulus in the presence of distractions from other stimuli, and the criteria used to make the judgement from ambiguous information (ie. the context that implies the consequences of a false positive vs. false negative)
Sensory adaptation
A decrease in sensitivity to a constant level of stimulation
Synthesia
Rare disorder where a person’s senses are linked. ie. they can taste colors, or when seeing a certain number, it has a color even though it is printed in black and white.
Extraordinary sense perception
The sense that something is about to happen and then it happening. It was mathematically proved to just be a coincidence, rather than an actual sense.
Process of seeing
Light first passes through the cornea, which is eye’s thick transparent outer layer, which focuses incoming light. The light then hits the lens, where it is bent further inward and focused to form an image on the retina. The retina contains receptors that then transduce light into neural signals.
The iris
The circular muscle that can contract or expand to let in less or more light into the eye.
Accommodation
The process where muscles behind the iris change the shape of the lens. They flatten it to focus on far objects and thicken it to focus on nearer objects. As people get older, the lens hardens and becomes more difficult to focus.
Rods vs. cones
Rods respond at extremely low levels of light and are primarily responsible for night vision. Rods don’t support color vision and are poor at detecting details. On the other hand, cones are less sensitive to low levels of light, and are primarily responsible for color vision and detail in vision.
Light transduction
Photopigments in the retina are protein molecules that become unstable and split apart when light hits them. The splitting of photopigments alters the membrane potential of photoreceptors, which triggers action potentials in downstream neurons. Cells in the middle layer then pick up these signals and perform a complicated series of computations that then converge to the ganglion cells. Ganglion cells are the first neurons in the visual pathway with axons, and are the first to generate action potentials. These signals then travel along the axons which are clumped together as the optic nerve and travel to the thalamus and then to the occipital lobe.
Approx. how many rods and cones does a retina hold
about 120 million rods and 6 million cones.
The fovea
Near the center of the retina, cones are densely packed in a region called the fovea. For the rest of the retina, their concentration slowly fades nearer the outer rim. Conversely, no rods are in the fovea, and rods have higher concentration closer to the rim.
Optic chiasm
half the axons of both optic nerves cross to the opposite side of the brain because the left side of each eye goes to the right brain and the converse for the left brain.
Ventral stream vs. dorsal stream
The lower stream of visual stimulus is the ventral stream, which is specialized in the perception and recognition of objects. The upper stream is the dorsal stream which is key for determining where an object is and relating it to other objects in a scene.
object anosia
Rare condition that is usually the result of damage to the prefrontal cortex, that causes people to be unable to identify objects
trichromatic theory
Says color vision is the result of the interactions of three different types of cones, which are receptive to red, green, or blue color waves. The theory posits that from these three, the rest of the colors we see are built from their interaction
opponent process theory
According to this theory, red and green are opposite colors, as are blue and yellow. This is inspired from when staring at a red image for a long period of time and then looking away, there is a green afterimage, and similarly for blue and yellow. The theory is that the red photopigments get tired while staring at red, and since the green receptors are not tired, the afterimage becomes green. It is theorized that the perception of “oppositeness” of red and green and blue and yellow is a consequence of processes in the ganglion cells which, for the red and green case, are excited by long wavelengths (red), and inhibited by medium ones (green).
List and define the 3 dimensions of color
hue, saturation, and lightness. Hue is determined by the wavelength, saturation is the purity of the color, and lightness is the color’s perceived intensity
The Gestalt perceptual grouping rules:
Proximity, Similarity, continuity, closure, and illusory contours.
Binocular depth cues (what they are + list 2)
available from both eyes and contribute to bottom-up processing. Includes stereoscopic vision and convergence.
Monocular depth cues (what they are + list 6)
available from each eye and provide organizational information for top-down processing. Includes: Occlusion, relative size, familiar size, linear perspective, texture gradient, and position relative to horizon.
Stereoscopic vision
The ability to determine distances to and between objects based on the angles that object makes with each eye
Convergence
The way the eye muscles turn the eyes inward when we look at nearby objects. The brain knows how much our eyes are converging and uses this information to determine distances
Occlusion
a nearby object blocks a faraway object
Relative size
far off objects project a smaller retinal image than close objects.
Familiar size
Because we know how objects are normally sized, we can tell how far away they are based on their size of retinal images.
Linear perspective
seemingly parallel lines converge at infinity
Texture gradient
as a uniformly textured surface recedes, its texture continuously becomes denser.
Position relative to horizon
all else being equal, objects below the horizon that appear higher in the visual field seem further away, and visa versa for above the horizon.
Motion aftereffects + what they give evidence for
when you gaze at a moving image for a long time and then look at a stationary scene. The stationary scene will temporarily look like it is moving in the opposite direction as the moving image. These give strong evidence for the existence of motion-sensitive neurons in the brain
Stroboscopic movement
how movies work
Object constancy
our brain tends to view objects as constant even if there exists perceptual data that might indicate otherwise.
What sensory input in the eye usually determines our perception of an object’s size?
The size of a retinal image.
