Angle of Regard Theory
objects appear smaller when the head is tilted up than when held parallel to the ground
Apparent Distance Theory
Earth's terrain causes moon to appear further away and thus bigger at the horizon
two lights blinking on and off will, at the proper frequency, appear to be one light that is moving
if a stationary small light in complete darkness is fixated, it will eventually appear to be moving erratically
after adapting to motion in a particular direction, the visual world appears to be moving in the opposite direction
disorder in which lines of one orientation are in focus while lines of other orientations are not
inability to bring objects into focus during old age
nearest point that someone can bring into focus
the furthest point that someone can bring into focus
someone who does not have a lens
a period of neural plasticity when certain environmental stimuli must be present for normal brain development to occur
pressure changes in a medium that can be detected by auditory organs
Cone of Confusion
the set of all points that could produce a particular time and intensity difference between the two ears
What two factors determine an object's perceived size?
- Retinal size of a stimulus
- Perceived distance to the stimulus
What did Kaufman and Rock find was the best predictor of the size of the moon illusion?
the perceived distance to the horizon
What are the causes of the Phi Effect and the Autokinetic effect?
- Phi Effect: cells some distance apart on the retina can be wired to excite another cell, indicating motion in a particular direction, when they are stimulated with a particular delay between them. The Phi Effect simulates this pattern of stimulation.
- Autokinetic Effect: To compensate for muscular fatigue, the eyes require abnormally strong signals from the brain. These abnormal signals are the same as would be required to track a moving object so the brain assumes the light is moving.
What sort of brain damage can lead to motion blindness?
damage to MT in both hemispheres
M.D. specializing in diagnosing an dtreating disorders of the visual system.
Eye care specialist who measures the refractive state of the eye and tests for certain diseases, and can prescribe lenses.
Person who makes optical instruments and lenses.
Specialist who works with people who have problems with binocular coordination.
What anatomical problems lead to astigmatism and presbyopia?
- Astigmatism: lack of spherical cornea
- Presbyopia: hardening of the lens and weakening of the ciliary muscles
What sort of lens is needed to correct myopia and hypermetropia?
- Myopia: Negative (concave) lens |(
- Hypermetropia: Positive (convex) lens |)
What does acuity measure?
the ability to detect high spatial frequency information (small things)
What do the numerator and denominator mean in the lines of an eyechart?
- Numerator: the distance, in feet, at which the test was conducted
- Denominator: the distance, in feet, at which the critical feature of the test symbol covers one minute of visual angle
What is PRK, LASIK, and Intacts?
- PRK: Epithelial layer of cornea is removed and laser reshapes the cornea.
- LASIK: 25% of cornea is cut into a flap and folded back. A laser reshapes cornea and then the flap is replaced, preserving the epithelial tissue.
- Intacts: Pieces of plastic are placed in cornea to change its shape.
What is the cause and treatment of Cataracts?
- 1. Congenital and inherited at birth
- 2. Aquired by injury or disease
- 3. Old age
- Treatment: Artificial lens implants, or removing lens and using spectacles to correct vision
What is the cause and treatment of Retinitis Pigmentosa?
- Cause: inherited disorder where photoreceptors slowly degenerate, starting with rods in the periphery
- Treatment: none presently, maybe artificial retinas or stem cells
What is the cause and treatment of Detatched Retina?
- Cause: photoreceptors become detatched from the pigment epitheliam
- Treatment: cryotherapy - eye is purposefully injured to create scar tissue that locks retina into place
What is the cause and treatment of Diabetic Retinopathy?
- Cause: Blood vessels serving retina start to leak. New blood vessels sprout across the retina and can cloud the vitreous humor with blood.
- Treatment: Laser photocoagulation - laser ios used to seal the leaks in the blood vessels
What is the cause and treatment of Glaucoma?
- Cause: Aqueous humor is not properly drained, resulting in increased intraocular pressure. This pressure compresses the blood vessels serving the optic nerve and the optic nerve fibers die.
- Treatment: drugs that decrease production of aqueous humor or remove blockage. surgery can also remove blockage
In the Hubel and Wiesel experiments on kitten visual development, how did shutting one fo the kitten's eyes during the critical period affect the eye itself, the LGN cells, and the cells in V1?
- Eye: completely normal
- LGN: Fewer cells devoted to the closed eye, but cells responded normally
- V1: abnormally preferred the open eye
What are two reasons why environmental stimulation might be necessary for normal perceptual development?
- 1. For binocular cells, neural plasticity may allow accomadation due to changing distance between the eyes.
- 2. As a survival mechanim, it may be wise to kill (or repurpose) unused cells.
What is the disadvantage and three advantages of compound eyes?
- Disadvantage: very poor acuity
- 1. Allow equal visibility across the entire visual field.
- 2. Always in focus.
- 3. Higher Flicker Fusion Frequency
What is the Flicker Fusion Frequency for humans and for insects?
- Humans: 10-24 Hz
- Insects: 300 Hz
What are two physiological reasons why birds have higher acuity vision than humans?
- 1. Bird photoreceptors are more densely packed than human photoreceptors.
- 2. Birds have much higher ratio of ganglion cells to photoreceptors.
What are the three different ways that nocturnal animals have developed to navigate in the dark?
- 1. Having very sensitive eyes
- 2. Having organs sensitive to heat rather than light
- 3. By using sonar
What is the range of frequencies that bats use for echolcation?
How do bats prevent damage to their eardrums when using their sonar?
suppress the vibration of the eardrum just prior to sending a signal
What visual abilities are best in humans (relative to other animals)?
What is the cause of the Poggendorf Illusion?
Blur by the optic media, lateral inhibition in retina, and processing strategies all affect this illusion.
What is the cause of the Wundt-Hering Illusion?
Large number of small Poggendorf Illusions.
What is the cause of the Ponzo Illusion?
Linear Perspective and Texture Gradients make the top bar appear further away and thus bigger than bottom bar.
What is the cause of the Ames Window Illusion?
Retinal image is consistent with both a trapezoidal window rotating or a rectangular window that switches direction every 180. Because we are use to seeing rectangular windows, our visual system prefers that interpretation.
What is the cause of the Wagon Wheel Illusion?
If frame rate of a movie is out of synch with the rotation of the wheel, the image of the wheel on the retina can be more consistent with the wheel spinning backwards.
What are the units of measuring sound frequency and amplitude?
- Frequency: Hertz (Hz)
- Amplitude: Decibels (dB)
Write the formula for decibels and know what each symbol in the equation means.
- dB=20 log (P/Po)
- dB: Decibels
- P: Pressure of soundwave being measured
- Po: Reference pressure
What are the psychological correlates of frequency and amplitude?
- Frequency: Pitch
- Amplitude: Loudness
To what frequency range is the human auditory system able to respond?
20 Hz - 20,000 Hz
List the three structures of the outer ear.
- Tympanic Membrane
What is the function of the Pinna and the Tympanic Membrane?
- Pinna: Appears to help amplify and localize high frequency sounds
- Tympanic Membrane: Vibrates in response to pressure changes in the atmosphere
What are the functions of the Ossicles?
- 1. Amplify tympanic vibrations
- 2. Protect the ear from loud sounds
What are the functions of the Oval Window, the Basilar Membrane, and the Hair Cells?
- Oval Window: transmit vibrations to the fluid in the cochlea
- Basilar Membrane: vibrates differentially, depending on the frequency of the sound
- Hair Cells: hen the region of the Basilar membrane below a particular hair cell is bent, the hair cells attached to that region release neurotransmitters that stimulates particular neurons in the auditory nerve.
What are the effects of bilateral removal of the auditory cortex?
- 1. Inability to distinguish different tunes
- 2. Inability to distinguish changes in the duration of tones
- 3. Inability to localize sounds
- 4. Inability to determine which ear is being stimulated
Explain Von Bekesy's Place theory of frequency perception.
Different places on the basilar membrane vibrate in response to different frequencies. The hair cells being stimulated by the region with the greatest amount of vibration indicate the frequency that is present.
What is the evidence for the Place theory?
- 1. A strong relationship exists between the frequency of the stimulus and the place of greatest basilar membrane vibration.
- 2. Selective deafness experiments show damage restricted to the hair cells at a particular basilar membrane location.
Explain Rutherford's Frequency theory.
The basilar membrane vibrates at the same frequency as the stimulus. Every time the basilar membrane vibrates, it causes an action potential in the Auditory Nerve. Thus, the rate at which the auditory nerve fires codes the frequency of the stimulus.
When two tones are presented simultaneously, what is perceived if the tones are separated by 1-15 Hz, the tones are separated by mroe than 15 Hz but less than the critical bandwidth, or the tones are separated by more than the critical bandwidth?
- 1-15 Hz: One tone widway in frequency between the two tones is perceived that ossilates in loudness at the same frequency as the difference between the two tones. (beats)
- More than 15 Hz: A single tone midway in frequency between the two tones is perceived but it sounds "rough"
- Critical Bandwidth: Two separate tones are perceived
List the two monaural cues for localizing sounds.
List the two binaural cues.
- Interaural Time Difference
- Interaural Intensity Difference
When is the interaural intensity difference most effective for localizing sounds?
When localizing high frequency sounds
How can we overcome the Cone of Confusion?
Moving our head