Midterm 1 Flashcards
What is Plato’s theory of forms?
we can never be sure of what our senses are telling us, we can only be certain of reasoning
What is anamnesis?
- Our immortal souls are made of left-overs of a greater “cosmos-soul” that had universal knowledge
- We lost this knowledge when our souls were incarnated in our imperfect bodies
- We must recover this knowledge by trying to “remember” what we “forgot”
Who is John Locke?
- Empiricist
- Tabula rasa: humans are blank pieces of papers on which experience leaves its mark
- Experience –> simple ideas –> complex ideas
Who is David Hume?
- Empiricist
- Inference of necessary cause and effect (B has to follow A) relationship is invalid, but psychologically we believe there is cause and effect
- Beliefs are caused by psychological “habits”
Who is Immanuel Kant?
Critique of pure reason
- We may never really know the thing-in-itself (Noumenon)
- All we know is the impression that the noumenon exerts on our senses (Phenoumenon)
Who is Thomas Bayes?
- Perception is the process of inferring what’s out there in the world based on the input of our senses
- Sensation is the input; perception is a probabilistic inference that integrates that sensation with our prior knowledge of the world
- At each stage, feedforward information coming from lower levels is merged with inferred knowledge coming from higher levels
What is the just noticeable difference (JND)?
the smallest change in a stimulus that can be detected.
What is discriminability?
How easy it is to notice a small difference in terms of physical intensity
- Higher weber fraction (ex: 0.3) means lower discriminability
- High discriminability = NO NOISE
What is the difference threshold?
The smallest difference you can perceive BETWEEN TWO STIMULI
What is the absolute threshold?
the smallest level of stimulus that can be detected, usually defined as at least half the time
What is noise in perception?
whichever physiological or psychological processes that can influence our perception of that external stimulus in an unpredictable manner
What is the method of constant stimuli?
several intensities are systematically tested in a random order
What is the method of limits?
ascending/descending cycles; change in direction when a “yes” or a “no”
What is the method of adjustment?
let the participant increase/decrease intensity in order to identify the threshold
What is the staircase method?
go back as soon as there is a change in response
What is sensitivity?
the capacity to detect a sensory signal when there is one
What is transduction?
the physical stimulus interacts with a specific receptor located on a peripheral sensory neuron and causes the neuron to fire (the stimulus is transduced into an electrical signal)
What is transmission?
when action potential occurs; sodium enters the cell, depolarizing it to open more voltage-gated sodium channels down the axon
What is a photon?
a quantum of visible light (or other form of electromagnetic radiation) demonstrating both particle and wave properties
What is accomodation?
the process in which the lens changes its shape, thus altering its refractive power
What is the retina?
a light-sensitive membrane in the back of the eye that contains rods and cones
What is a diopter?
Measures the focusing force of the lens
- the reciprocal (1 divided by) of the focal length
What is the focal length?
distance between the lens and the point at which light rays converge (the focus)
What is emmetropia?
the happy condition of no refractive error
What is myopia?
when light is focused in front of the retina and distant objects cannot be seen sharply (nearsightedness)
What is hyperopia?
when light is focused behind the retina and near objects
What is presbyopia?
a form of hyperopia associated with old age- eventually the lens will lose its elasticity
What is astigmatism?
unequal curving of one or more refractive surfaces of the eye, usually the cornea
- multiple focal points
What is the optic disk?
The white circle where the arteries and veins that feed the retina enter, and where the axons of the ganglion cells leave the eye towards the brain
- The portion of the retina contains no photoreceptors and is therefore “blind”
What is the macula?
The dark spot that’s situated in the center of eye (immediately behind your lens)
- It contains a high density of photoreceptors and is responsible for central vision
What is the visual angle of an object?
corresponds to the size of the object on the retina, not its actual size
What is the photopic system?
Responsible for daytime vision, has acuity, and very low sensitivity
- If there isn’t a lot of light, the system won’t function properly
What is the scotopic system?
Low acuity, very sensitive to light
- If you don’t have a lot of light, it will still allow you to see
What is dark adaptation?
The process by which sensitivity to low light is increased in the visual system
What is the cone-rod break?
Number of active pigments in rods is equal to the number of pigments in cones
- Rods will continue to gain more
What is maximum sensitivity?
the reservoirs for both rods and cones are full
What is the receptive field?
the region on the retina in which stimuli influence a neuron’s firing rate
What are p ganglion cells?
Connect to the parvocellular pathway
- Receive input from midget bipolar cells
What is the parvocellular pathway?
involved in fine visual acuity, color, and shape processing, poor temporal resolution but good spatial resolution
What are m ganglion cells?
Connect to the magnocellular pathway
- Receive input from diffuse bipolar cells
What is the magnocellular pathway?
Involved in motion processing, excellent temporal resolution but poor spatial resolution
- Larger receptive fields than parvocellular
What does high convergence mean?
projects onto the same retinal ganglion cell (less sensitivity)
What is acuity?
sharpness of vision
What is one unit of arc?
One unit of arc corresponds to one degree
-There are 60 minutes in a degree (or in a unit of arc).
What is spatial frequency?
Cycles of a grating per unit of visual angle (in degrees)
- Aka the number of times a pattern repeats per unit area
What are Koniocellular cells?
very small cells in between the manocellular and parvocellular sections
What is contralateral representation?
left LGN receives info from the right visual field and vice versa
What are diffuse bipolar cells?
receives input from multiple photoreceptors
What are midget bipolar cells?
receives input from a single cone
