Note for PSYC 329 with Professor Petersonm at UA
Note for PSYC 329 with Professor Petersonm at UA
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Date Created: 02/06/15
Psych 329 Exam 1 Grading Rubric Below are the components of each question that would constitute full credit 1 Discuss quotsparse codingquot with respect to specificity coding and distributed coding Define all terms 8 points Graded by leanMarie Zpts define sparse coding Zpts define speci city coding 2 pts de ne distributed coding Zpts discuss how sparse coding relates to specificity and distributed coding 2 What is the magnitude estimation procedure and what does it reveal regarding how perceived intensity grows relative to physical intensity 8 points Graded byeanMarie 4pts 7 definediscuss the magnitude estimation procedure need to point out that it is a psychophysical method in which the subject assigns numbers to a stimulus that are proportional to the subjective magnitude ofthe stimulus 4pts discuss how perceived intensity grows relative to physical intensity need to point out that there is no one to one correspondence between perceived intensity and physical intensity it varies based on the stimulus Some ofyou used the examples of shock and light to describe this which I gave credit for 3 What does the illustration below illustrate Does it show that we have a distorted picture in our brains 8 points Graded byleanMarie RETINA VISUAL CORTEX 4 pts It illustrates the cortical magnification factor The circle in the middle represents the relative number of ganglion cells devoted to representing the fovea in the retina on the left and in the visual cortex on the right A brief definition of the Cortical Magni cation factor is good m one can also say that the center circles represent the relative AREA in the retina and the visual cortex devoted to processing the fovea not the rel number of neurons The cones are small and packed into the fovea and there39s virtually a onetoone relationship between cones and cortical cells The rods however have a many to one connection scheme 4 pts No we don39t have a picture in our brains Once light energy is transduced by the receptors it39s all electrical signals from there on in The magnification of the representation of the fovea accounts in part for our visual acuity 4 Brie y discuss whether we have direct access to objects in the world or whether perception is indirect 8 points Graded by IeanMarie 8 pts We perceive the world through our senses Naive realism is not correct A brief example or two supporting why na39ive realism is not correct I was generous here trying to give as much credit as possible for answers that hinted at or suggested this main point 5 What is nearsightedness Where does the lens of a nearsighted eye focus the image What is one cause of nearsightedness 6pts Graded by Ryan Answer Nearsightedness is the inability to see distant objects clearly 2pts The lens focuses the image in front of the retina 2pts Causes ofnearsightedness include for example an elongated eyeball or excessive curvature of the cornea 2pts Essays ZOQoints each Spend 10 minutes on each 6 When we want to see stars better at night should we look with our central vision or out of the corner of our eyes Iustify your answer with reference to a distribution of rod vs cone receptors b acuity vs sensitivity define these terms c low vs high convergence define these terms Graded by Ryan Example answer necessary elements highlighted To see stars we should look out of our peripheral vision This is because the distribution of receptors in the retina is such that rods dominate in the periphery There are some cones in the periphery but only cones exist in the fovea where our central vision is focused The reason rods are preferable is because they have a higher sensitivity to light compared to cones This means that they can respond to a lower amount of light than a cone in the fovea could One reason for this increased sensitivity is that rods have a large amount of convergence onto their downstream targets from a broad area of the retina which allows for a higher probability that light within this region will be detected The problem with this set up however is that since the downstream cells cannot tell where in the broad receptive field the light has hit the acuity provided by these cells is low Cones however have a very low convergence to downstream cells such that there is only a very small region where light can hit in order to stimulate a given pathway This instead allows for detailed information acuity of where the light has been received Thus given the reasons for the increased sensitivity of rods peripheral vision would be more effective at seeing them 7 Is it true that subliminal stimuli are never perceived In your answer discuss how thresholds are determined and how absolute threshold is defined Define all terms related to the class 20 pts Graded by IeanMarie 5pts No it is not true that subliminal stimuli are never perceived 5 pts How are thresholds determined basic overview ofprocedure 5pts Method oflimits adjustment constant stimuli mentioneddescribed 5pts Definition of absolute threshold 8 The picture below illustrates the simultaneous contrast illusion A Brie y describe the illusion and the conditions that produce it B Explain why the illusion occurs with reference to the relative firing rates of neurons with receptive fields A and B Be sure to identify the type of receptive field illustrated by A and B Graded by Ryan Example answer necessary elements highlighted AThe illusion of simultaneous contrast arises when two regions emitting light with identical characteristics are surrounded by a darker region in one case and a lighter region in another case The illusion arises because the region surrounded with darker contrast appears lighter than the identical region surrounded by lighter contrast BIn this example we are assuming that with an increase in firing rate comes an increase in the subjective experience of lightness That being the case as shown in the illustration we should consider the neural firing rates of neurons with receptive fields spanning the border of the two contrasts Both of these neurons are coding for the subjective color that we perceive the inner box to be as the receptive field falls mostly within this region Give that these are oncenter offsurround receptive fields light hitting the center will increase their firing rate while light hitting their surround will decrease their firing rate Given that the majority of each receptive field is receiving identical stimuli from the inner gray boxes the difference in firing rate must be entirely due to the portion of the inhibitory region of the receptive field that falls on the surrounding contrast In A the darker color is stimulating the inhibitory region less and therefore the cell is being less inhibited and its firing rate should be relatively high thus coding for a lighterpercept In B on the other hand the inhibitory region is being stimulated by a lighter contrast and therefore increasing the inhibition on the neuron in consideration This will cause the firing rate of this neuron to be low relative to the rate ofneuron A and therefore the center box ofA will appearto us to be brighter than B m a
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