Sensation & Perception Flashcards
Absolute threshold
Smallest magnitude of stimulus that can be perceived 50% of the time. Minimum stimulus energy needed to activate the sensory system.
Just noticeable difference
Proposed by Ernst Weber, aka difference threshold. The smallest difference between two stimuli that can be consistently and accurately detected on 50% of trials.
Weber’s law
A mathematical model of the difference threshold stating that the magnitude needed to detect physical change in a stimulus is proportional to the absolute magnitude of that stimulus. Thus, the more intense the stimulus, the greater the change that must be made in it to be noticed.
Signal detection theory
States that there is no absolute threshold. Detection depends on the intensity of the physical energy and internal factors like cost & benefits associated with the detection.
Response bias
Measures how risky the subject is in sensory decision-making; based upon non-sensory factors
Transduction
The translation of physical energy into neural impulses or action potential. Occurs at the receptors - cells specialised for conversion of one kind of energy.
Subliminal perception
Presumed ability to perceive stimulus that is below the threshold of conscious experience
[subliminal messaging & visual priming]
Sensory adaptation
Reduced sensitivity to unchanging stimulus over time
eg: feeling of tongue in the mouth, clothes rubbing against skin
Cornea
Curved transparent layer through which light enters the eye
Pupil
Opening in the eye through which light enters - dilates and constricts based on amount of light
Iris
Coloured part of the eye, consisting of involuntary muscles that control the size of the pupil
Lens
Curvature right behind the iris, to bend and focus light on the retina
Retina
Complex sheet of cells and fibres at the back of the eyeball, contains rods and cones
Fovea
Area in the center of the retina with the highest concentration of cones. Visual acuity highest. Used when we want to see things clearly.
Optic nerve
Bundle of nerves located the back of the eye, carries visual info to the brain
Blind spot
Point in the region of the retina where the optic nerve leaves and blood vessels enter and leave the retina
Duplicity theory of vision / Duplex theory
The theory that vision depends on the activity of two types of receptors: rods and cones
Rods
Allow perception of achromatic colours, used in levels of low light. Not involved in colour vision. 120 million.
Cones
Used to see chromatic and achromatic colours. Responsible for greatest acuity and daylight vision. 6 million.
Trichromatic theory
By Young & Helmhotz - A physiological basis of color vision stating that the retina has 3 types of cones sensitive to different wavelength of light [red, blue & green]
Opponent process mechanism of vision
By Hering - Theory that there are 3 types of cones that have two types of colour receptors each which respond to two different wavelengths.
Blue or Yellow; Red or Green; Black or White
Connection between receptors and optic nerve
Rods and cones connect with bipolar neurons that connect with ganglion cells. Ganglion cells form the optic nerve.
Ganglion cells represent a combination of rods and cones, more rods than cones, ergo cones are more sensitive to fine detail.
Visual pathway in the brain
From the optic chiasm, the information goes to several different places in the brain: the lateral geniculate nucleus of the thalamus, the visual cortex in the occipital lobe, and the superior colliculus
Optic chiasm
The location at the base of the brain at which the optic nerves from the two eyes meet. In humans, the nerve fibres from the nasal half of each retina cross, so that each hemisphere of the brain receives input from both eyes.
Feature detection theory
Proposed by Hubel & Wiesel - certain cells in the cortex are maximally sensitive to certain features of stimuli. Simple, complex & hypercomplex cells.
Rhodopsin
Photochemical made of derivative of vitamin A, retinal and protein, opsin. Present in rods.
Simultaneous brightness contrast
The apparent enhanced difference in brightness resulting from simultaneous stimulation by two stimuli of differing brightness. For example, a grey disk looks darker on a white background than on a black background.
Afterimage
Sensation what appears after a prolong or intense exposure to a stimulus
Terms in depth perception
Monocular cues:
- relative size
- interposition [overlapped object is considered further away]
- height cues
- motion parallax [objects that are closer appear to move faster (in opposite direction) than objects that are further (in same direction)]
- linear perspective
- texture gradient [closer are grainier, farther are smoother]
Binocular cues:
- convergence [brain takes feedback from eye muscles that move inwards when seeing a closer object]
- retinal disparity [retinal points that give rise to different principal visual direction and diplopia] [its also known as stereopsis]
Figure-ground relationship
Dividing the world into two parts: the discrete figure and background against which it stands out
Gestalt laws of perception
Proximity - closer are grouped together
Similarity - sameness grouped together
Good continuation - point connected by a straight or curved line seen as together
Closure - figures seen as more complete than they really are
Common region - same region is seen as together
Law of prägnanz (or good figure)
States that perceptual organization will always be as “good” (i.e., regular, simple, symmetrical, etc.) as possible
Bottom-up processing
Process of object perception that responds directly to components of the stimulus based on features and combines the component to form a whole pattern
Top-down processing
Proposed by Richard Gregory
Object perception guided by memories and expectations to recognise the whole object and then recognise components
It is constructive
Apparent motion
When two or more stationary lights flicker in quick succession they are perceived as one light moving
Phi phenomenon
Induced motion
Stationary light appears to be moving when background is moving
Autokinetic effect
Stationary light in a completely dark room appears to be moving erratically due to no frame of reference
Motion aftereffect
The perception that a stationary object or scene moves following prolonged fixation of a moving stimulus. The illusory movement is in the opposite direction to the movement of the stimulus that induced the effect.
[waterfall effect]
Perceptual constancies
Tendency to perceive aspects of world as unchanging even if sensory input shifts
Size constancy
Tendency for the perceived size of an object to remain constant despite variations in the size of its retinal image
Shape constancy
Tendency for the perceived shape of an object to remain constant despite variations in the shape of its retinal image
Light/brightness constancy
Tendency for the perceived lightness of an object to remain constant despite changes in illumination
Colour constancy
Tendency for the perceived color of an object to remain constant despite changes in the spectrum of light falling on it
Illusion
When perception yields false interpretation of reality
Theory of misapplied constancy
When looking at illusions, we interpret certain cues as suggesting that some parts are further away than others
Size-distance invariance
When estimating size of an object, we take into account the size of the image casted on the retina and apparent distance
Cocktail party phenomenon
Ability to focus on a single voice in a noisy environment
Selective attention
Attending to certain aspects of the environment while others are moved to the background. Maximize info from object of focus and reduce sensory interference from others.
Perceptual learning
An increase in the ability to extract information from the environment as a result of experience or practice with the stimulation coming from it
Perception can be molded through learning. Eg: People who work at a certain job - ability to pick up on slightest change in stimuli compared to others. Blind people.
Perceptual cognitive styles
Dimensions that determine variation in perceptual style:
- degree to which their perceptions are flexible or constricted; more flexible has wider focus of attention and less affected by interfering influences and less dominated by internal needs
- field dependence or independence; dependent people find it hard to break down what is perceived to elements and emphasize whole over parts
Structure of the ear
Pinna in the outer ear picks up energy which travels through the auditory canal into the eardrum.
Oscillation of the membrane of the eardrum moves 3 small bones called ossicles. Now the vibration is carried from middle ear to cochlea in inner ear. Energy is amplified in middle ear.
Cochlea contains 3 fluid-filled canals: vestibular canal, cochlear canal, tympanic canal
The fluid in the cochlea cause hair cells to have a bending motion. This bending motion transducts mechanical energy into nerve signals. These signal go to the auditory nerve, into the brain.
Inattentional blindness
Unattended stimulus doesn’t register itself in individual’s consciousness
Human eye is capable of perceiving ____ nanometers
700-400
Myopia
Near-sightedness
Hyperopia
Far-sightedness
Seat of light sensitive photoreceptors
Retina
Human ear can hear _____ Hz
20-20,000
Frequency theory by Ernest Rutherford
Rate of firing of auditory neurons is equal to the frequency of the sound waves
If a neuron fires at a rate of 100, the frequency is also 100 Hz.
Place theory of pitch perception by Helmholtz
Specific points in the cochlea, fluid waves peak depending on the frequency of the waves which also influence the bending of the hair cells
2 types of hearing loss
Nerve deafness: Damage of receptors in the inner ear or auditory nerve usually due to loud noise
Conduction deafness: Related to the problems of the mechanical systems (outer and middle ear) which are responsible for transmitting sound waves to the cochlea.
Proprioception
Sense of body position
Kinesthesis
Sense of movement
Intense stimuli are received by pain receptors called _____, which are found at the ends of nerves that extend from the spinal cord to the skin.
Nociceptors
Gate control theory
The hypothesis that the subjective experience of pain is modulated by large nerve fibers in the spinal cord that act as gates, such that pain is not the product of a simple transmission of stimulation from the skin or some internal organ to the brain. Rather, sensations from pain receptors have to pass through these spinal gates to the brain in order to emerge as pain perceptions.
The status of the gates, however, is subject to a variety of influences (e.g., drugs, injury, emotions, possibly even instructions coming from the brain itself), which can operate to shut them, thus inhibiting pain transmission, or cause them to be fully open, thus facilitating transmission.
