Sensation and Perception Flashcards
Sensation
The process by which our sensory organs receive stimulus energies from the environment and transduce them into the electrical energy of the nervous system. Stimulation of sensory organs (what our senses do).
Transduction
The transformation of sensory stimulus energy from the environment into neural impulses. Translation of physical energy from the environment to neural signals.
Perception
The neural processing of electrical signals to form an internal mental representation inside your brain of what’s on the outside. Processing, organization, and interpretation of sensory input (what our brains do (internal representation of the world. Experiences can play a role)). May not be what is actually happening or real.
Psychophysics
The study of the relationship between the physical characteristics of environmental stimuli and our mental experience of them (what can we detect? How intense does it have to be? How sensitive are we?).
Absolute Threshold
The minimum amount of stimulation necessary for someone to detect a stimulus half of the time. It isn’t stable (can differ between people or overtime).
Conservative Response Bias
Not giving a response unless you are a hundred percent sure.
Liberal Response Bias
Giving a response even if you are not sure about it in order to do “well”.
Signal Detection Theory
An approach to measuring thresholds that takes into account both the intensity of the stimulus and psychological biases for a more accurate assessment.
Hits
Seeing the stimulus.
Misses
Not seeing the stimulus.
False Alarms
Seeing the stimulus when there is none.
Correct Rejections
Not seeing the stimulus when there is none.
Difference Threshold/Just-Noticeable Difference (JND)
The minimum difference required between two stimuli for an observer to detect a difference half the time (just noticeable difference). Depends on the intensity of the original stimulus.
Weber’s Law
The observation that the likelihood of perceiving a stimulus change is proportional to the magnitude of the stimuli. It’s not about the absolute amount of stimulus that is added/taken away, it’s about the proportion. In order to notice a difference, the two stimuli must differ by a constant proportion (lighting is 8%, object weight is 2%, and sound is 0.3%).
Plasticity of Perceptual Systems
When neurons change their sensitivity and selectivity with experience. Ex. if you got a bee sting when you were young, you may have increased sensitivity for detecting bees buzzing around you.
Adaptation
A phenomenon whereby an individual stops noticing a stimulus that remains constant over time, resulting in enhanced detection of stimulus changes.
Sensory Adaptation
Occurs at the level of sensory receptors.
Perceptual Adaptation
Occurs higher up in the brain.
Aftereffects
Opposing distortions that occur after adaptation (you perceive the opposite of what your senses and brain have adapted to).
Wavelength
The distance between any two consecutive crests or troughs of a wave.
Frequency
The number of cycles per second of a wave.
Amplitude
The height of the crests of a wave.
Pupil
A hole in the iris where light enters the eye. Controls the amount of light that goes in. The black portion of the eye.
Iris
The coloured muscle circling the pupil (aka the eye colour).
Lens
A membrane at the front of the eye that focuses the incoming light on the retina. More focus based on distance (second step of focusing).
Accommodation
Adjustment of the lens’s thickness by specialized muscles in order to change the degree to which it bends light.
Presbyopia
A condition where the lens of the eye becomes less elastic and the eye’s ability to focus via accommodation weakens making it difficult to see things that are too close.
Retina
A surface on the back of the eye that contains the photoreceptor cells, mostly rods than cones that convert light into neural impulses. Used for transduction.
Rods
Photoreceptor cells that primarily support nighttime vision. All have the same type of photopigment. 120 million cells, high sensitivity (act in low light conditions), low acuity (less sharp), primarily in the periphery (outside), black and white vision. Contain only one type of photopigment.
Cones
Photoreceptor cells that are responsible for high-resolution colour vision. Contain one of three varieties of photopigments which allow us to perceive colours (colour vision only occurs in the cones). 5 million cells, low sensitivity (act in high light conditions), high acuity (very sharp), primarily in fovea (the center), colour vision. Contain multiple types of photopigments.
Visual Transduction
When cells convert light energy into electrical energy.
Nearsightedness/Myopia
When faraway objects are projected too far in front of the fovea.
Farsightedness/Hyperopia
When a near object is shown too far in the back of the eye.
Optic Nerve
A bundle of axons that converge from the retina and transmit action potentials to the brain.
Blind Spot
An area in the middle of the visual field where there are no photoreceptors and no information can be received. The brain tries to fill in the blanks using the information from the surrounding regions of the retina.
Fovea
A small pit in the center of the retina that is densely packed with cones.
Foveation
A process in which eyes are trained to move constantly in order to focus different stimuli directly onto the fovea.
Acuity
The sharpness or specificity of perception supporting the discrimination of stimuli. The cones specialize in acuity, supporting daytime vision when light is abundant and we see things in high-resolution colour.
Sensitivity
The ability simply to detect a stimulus is present. The rods provide more sensitivity, primarily supporting nighttime vision when light is limited and we see things in grainy shades of gray.
Achromatic Colours
White, black, and any shade of gray (do not result in a distinct colour or chromatic experience).
Trichromatic Theory
A theory of colour perception stating that three types of cone cells, each most sensitive to a specific wavelength of light, work together to produce our perception of a multicoloured world. We have three kinds of cones (L, M, S).
Colour-Blindness
Often results from a deficiency in one of the three types of cones.
Dichromacy
Having only two cones.
Monochromacy
A rare condition in which individuals are born with only one kind of cone. Have no colour perception (see all wavelengths as various shades of gray).
Opponent-Process Theory
A theory of colour perception stating that information from the cones is separated into three sets of opposing or opponent channels in the ganglion cell layer. Bipolar cells combine inputs from different cone types. Ganglion cells respond in an antagonistic way to oppose pairs of wavelengths (ex. activated by red but inhibited by green).
Primary Visual Cortex
The visual sensory receiving area in the occipital lobe.
Retinotopically
A way to describe the organization of the primary visual cortex. The adjacent portions of the retina connect with adjacent areas of the visual cortex.
Feature Detectors
Specialized cells in the visual cortex that respond to basic features such as lines, edges, and angles.
Visual Association Cortex
The region of the brain where objects are reconstructed from prior knowledge and information collected by the feature detectors.
Prosopagnosia
A visual disorder in which individuals are unable to recognize the identity of faces. It is not due to a deficit in vision, language, or intelligence.
Ventral Pathway/Visual Stream
Travels along the temporal lobe. Specialized to address the “what” questions. Damage to this pathway impairs object recognition. Recognizes objects, conscious perception of details attaching meaning to what we see. Conscious perception and awareness.
Dorsal Pathway/Visual Stream
Joins the parietal lobe. Specialized to address the “where” and “how” questions of object recognition. It supports location, depth, and motion and thus influences how we interact with objects. Locates objects spatially. Performs simple actions (head and eye movements, reaching). Largely below conscious awareness.
Akinetopsia
A deficit in perceiving motion such that those with this condition experience the world as a series of static snapshots rather than a continuous flow of events.
Phi Phenomenon
A visual illusion in which the flashing of separate images in rapid succession is perceived as fluid movement.
Gestalt Psychology
A school of psychological thought that attempted to explain how various elements group together to form objects, arguing that perception is more than a simple piecing together of building blocks. How we group visual information to form perceptions (the whole is greater than the sum of the parts).
Binocular Cues
Depth information gathered from the separation between an individual’s two eyes. Results from seeing with both eyes.
Binocular Disparity
The magnitude of difference between the images projected on an individual’s two eyes.
Monocular Cues
Depth information that can be gathered by only one eye (available to either eye alone).
Size Constancy
The phenomenon whereby the brain adjusts its perception of distance in order to perceive an object’s actual size as constant, taking into account changes in retinal size.
Colour Constancy
The phenomenon whereby the brain adjusts its perception of colour to hold it constant taking into account changes in lighting conditions.
Bottom-Up Processing
Taking individual bits of sensory info and using them to construct a perception.
Top-Down Processing
Perceptions that are influenced by our expectations or prior knowledge.
McGurk Effect
What we see can influence what we think we hear ex. when the auditory component of one sound is paired with the visual component of another sound, it changes our perception of the sound.
Light
Electromagnetic radiation waves. Humans can see 390 nm to 750 nm.
Sclera
The white portion of the eye.
Cornea
Focuses the light, where light first hits.
Brain
Used for perception.
Photopigments
Change shape when absorbing light affecting the release of glutamate. The glutamate sends signals to adjacent bipolar cells (sensory neurons) and ganglion cells. Signal then travels to the brain via optic nerve (blind spot).
L
Red cones, long wavelengths.
M
Green cones, medium wavelengths.
S
Blue cones, short wavelengths.
Colour Blindness/Dichromacy
When people have fewer cones of a certain type than they should.
Deuteranomaly
Problems or missing M cones. Not seeing green properly.
Protanopia
Problems or missing L cones. Not seeing red properly.
Tritanopia
Problems or missing S cones. Not seeing blue properly.
Afterimages
When you look at an image for a long time then look away, you will see the opposing colours ex. if you stare at a red image and look away you will see a green image.
Visual Perception and the Brain
Information from the left visual field goes to the right side of the brain and vice versa regardless of which eye sees it. Information crosses sides at the optic chiasm. Optic nerve first connects with thalamus then travels to V1 (primary visual cortex (occipital lobe)). Involves cortical magnification (more information is received by the cones rather than the rods due to having more neurons) and the association cortex.
Blindsight
People who are cortically blind (damage to the occipital lobe) can still respond to visual stimuli that they can’t consciously see.
Superior Colliculus
An older evolutionary pathway that connections the information entering the retina directly to the dorsal visual stream.
Hollow Face Illusion
A study where people were able to accurately flick off targets in the hollow face. Visual action track (dorsal) isn’t fooled by the illusion we experience through the visual perception track (ventral) (deep down they knew that the mask was caved in). Our hands know what we don’t consciously perceive.
The Case of Dr. P
A man who mistook his wife for a hat. Was a distinguished musician that started to have difficulties recognizing faces and tried to put his wife’s head on as a hat and couldn’t tell that there was a problem. His speech was fine, meaning that his temporal lobe was still functioning. Was diagnosed with visual agnosia. Hypothesized tumor or degeneration of visual association cortex.
Visual Agnosia
An impairment in recognition of visually presented objects.
Gestalt Psychology Aspects
1) Proximity
2) Similarity
3) Continuity (we look for continuous lines and group the objects in that way)
4) Closure
5) Connectedness
Depth Perception
The ability to see objects in three dimensions although the image that strikes the retina is two-dimensional. Develops early in life (ex. visual cliff experiment).
Relative Size
A monocular cue. Objects that are farther away project smaller retinal images. Judges distance based on how large an object appears compared to other objects of known sizes.
Elevation/Relative Height
A monocular cue. Items that are higher in the visual field are perceived as being further away. Above the horizon line, objects that are higher are perceived as closer.
Interposition
A monocular cue. If one object partially obscures another, it is perceived as closer.
Linear Perspective
as parallel lines recede into the distance, they appear to get closer together (coverage at the vanishing point). The more lines converge, the greater the perceived distance. (One point perspective drawings)
Relative Motion (Movement Direction)
Objects in front of fixation point seem to move backwards and objects behind the fixation point seem to move forward.
Relative Motion (Movement Speed)
Close objects move fast and further objects move slower.
Retinal Disparity
A binocular cue. The difference between objects is projected on the two eyes. Objects further away from our line of focus appear at increasingly different locations on the retinas.
Ames Room
A room that appears to be normally shaped at one location so when a person moves, they appear to become much larger.
