What is the Difference Between Sensation and Perception

• What is the difference between sensation and perception? - Sensation: can categorize things o Visual form agnosia: inability to recognize common objects - Perception: having conscious awareness of properties of objects , can happen without sensation • Differentiate between “top-down” and “bottom-up” processing and their relation to knowledge. - “bottom-up” processing: process based on the stimuli, how the stimuli activates the sensory systems as is - “top-down” processing: influenced from knowledge (what we bring into the perceptual process) change our perception • What “underdetermined” problems does the visual system solve? - Recovering the useful structure of the physical world from the physical stimulation that hits our receptors - Determining the nature of this recovery and how it is accomplished • What is the problem with studying qualia empirically? - We can’t really measure qualia in terms of relationships between a stimulus and a perception because it happens in one’s head • What are theoretical construct and operational definitions? What is an example? - Theoretical construct: entities that we’re interested in but can’t observe (happiness, sadness, experience of color) - Operational definitions: external behavior that stands in to measure the construct we’re interested in (self rate happiness with a scale from 1-10, find the blue berry, what picture makes you saddest, reaction time) • What is the criterion of falsifiability? - Must be falsifiable on the basis of some physical observation • What is psychophysics? Describe the general psychophysical methods (method of limits, method of constant stimuli, method of adjustment, adaptive staircase) and how threshold is obtained from these methods. - Psychophysics: the study of defining quantitative relationships between mental experience and physical events - Absolute threshold: the smallest stimulus that can just be detected (a drop of perfume in a house, a teaspoon of sugar in a gallon of water) - Difference threshold: the smallest difference between 2 stimuli that we’re able to tell apart o Methods of limits ▪ Present the stimuli to participant in an order of intensity until the participant can’t identify it (Ex: light gradient) o Method of constant stimuli ▪ Present stimuli with intensities in random order (ex: different shades of light) o Method of adjustment ▪ Participant adjust the intensity of the stimulus (like using a knob) until he/she can’t detect it (ex: volume) o Adaptive staircase ▪ Stimuli intensity adjusts based on participants response - Magnitude estimation: measure how people quantify perceived difference between 2 stimuli o Response expansion: perceived magnitude increases more quickly than stimulus intensity (ex: electric shock) o Response compression: perceived magnitude increases more slowly than stimulus intensity (ex: brightness) • What are Marr’s levels of analysis? What question is asked at each level? Which are more and less abstract? - Computational: what does the system do? What problem is it solving? (most abstract) - Algorithmic: what steps does it take? (less abstract, more concrete) - Implementation: how are the steps instantiated in the system/brain? (most concrete) • What is the mind body problem, dualism, materialism? - Mind body problem: what is the relationship between the mind (the mental) and the physical body (matter) - Dualism: humans have both minds and body/brain separate from each other - Materialism: matter is the only reality, mind = brain • What are the major concepts in psychophysics? • What is accommodation? - Eyes when relaxed will form a crisp image of object on the retina (far point), if move object closer then far point will get shifted and image moves to back of retina eyes accommodate to change shape of lens to form sharp image using ciliary muscles • Explain why the “blind spot” exists, and why we are not usually aware of it. - “blind spot” – where the optic nerve leaves the eye (exists because there’s no receptors here) - Usually not aware because blind spot is not in macula where shapr image is formed, and the brain “fills in” the spot • Understand the spectral sensitivity of different receptors and how it relates to absorption spectrum. • Identify the key components of neurons. - Neurons – basic cellular units for processing information (100s of million in nervous system) - Components: o Dendrite – receiving input messages from neurons o Cell body o Axon/nerve fiber – outputting messages to other neurons • Define propagated response, and discuss how this is related to measuring activity in a single neuron. - Action potential is a propagated response – once triggered, signal travels down the axon without decreasing in size allow transmitting signals over long distances • Describe depolarization, hyperpolarization, inhibition and spontaneous firing rate. - Depolarization: caused by neurotransmitters as an excitatory synaptic potential increasing voltage close to the threshold of triggering an action potential - Hyperpolarization: inhibitory synaptic potential decreasing the voltage farther from threshold of triggering action potential - Spontaneous firing rate: • What is neural convergence? How does it relate to acuity in rods and cones? - Neural convergence: when a number of neurons synapse onto a single neuron (rods and cones synapse onto a ganglion cell) - Rods have higher convergence than cones - But cones have higher acuity than rods • Define and understand lateral inhibition. - Lateral inhibition: • What is a neural circuit? How does this concept relate to lateral inhibition and convergence? - Neural circuit: groups of neurons that are interconnected and will fire together as the result of stimulation neural convergence: how a number of neurons synapse onto a single neuron • Know the major differences between rods and cones. (e.g. sensitivity, acuity, color, distribution of the rods and the cones.) • What is the doctrine of specific nerve energies? - Nature of sensation depends on which sensory fibers are stimulated not how the fiber is stimulated - More specific later on: activation of target area in cortex was critical in experiment • Be able to describe the major events in vision from the distal stimulus to perception, and at what stage in the perceptual process these events occur. - When we see an object in the environment (distal stimulus), an image of the object is form by light reflecting from one of each point of the object onto our retina, a membrane at the back of the eye that contains light-sensitive receptors. This is also the proximal stimulus as the light energy from the object directly stimulates our visual sensory system. The cornea accounts for 80% of the eyes’ focusing power, and light refracted from the cornea enters through the pupil and iris dilates to regulate the input on both eyes (pupillary light reflex). When our eyes are relaxed, the far point is where the sharp image is created on the retina. As we move the object closer, our eyes will accommodate by changing the shape of the lens to re-create the sharp image. However, we will reach the near point as the closest we can bring an object and keep it in focus as it’s the most our ciliary muscles can constrict. Presbyopia is when our lens become harder and less flexible that ciliary muscles become weakened. Myopia (nearsightedness – can’t see distant objects) is when lens are too curved (eyeball is too long). Hyperopia (farsightedness – can’t see close objects) is when lens are not curved enough or eyeball is too short. • What does it mean to have an inverted eye? What is a feature of the eye that makes this less of a problem? • Describe all of the parts of the eye and what they do.