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Questions and Answers
What is the primary function of photoreceptors in the retina?
What is the primary function of photoreceptors in the retina?
- To protect the eye from external damage
- To convert light energy into electrochemical signals (correct)
- To focus light on the fovea
- To adjust the size of the pupil
Which part of the eye contains a high concentration of rods?
Which part of the eye contains a high concentration of rods?
- Cornea
- Pupil
- Fovea
- Periphery of the retina (correct)
What is the role of the fovea in the visual system?
What is the role of the fovea in the visual system?
- To provide peripheral vision
- To detect color in bright light
- To focus light directly onto its surface (correct)
- To filter out excess light
What range of wavelengths can humans perceive as visible light?
What range of wavelengths can humans perceive as visible light?
Which characteristic distinguishes rods from cones?
Which characteristic distinguishes rods from cones?
What substance makes up the majority of the eye's volume?
What substance makes up the majority of the eye's volume?
How does the brain perceive environmental stimuli?
How does the brain perceive environmental stimuli?
What happens to light as it enters the eye?
What happens to light as it enters the eye?
What defines viewer-centered perception?
What defines viewer-centered perception?
Which Gestalt principle states that we perceive visual arrays in a way that organizes different elements into a coherent form?
Which Gestalt principle states that we perceive visual arrays in a way that organizes different elements into a coherent form?
What is meant by perceptual constancy in visual perception?
What is meant by perceptual constancy in visual perception?
Which of the following is a monocular depth cue?
Which of the following is a monocular depth cue?
How does object-centered perception differ from viewer-centered perception?
How does object-centered perception differ from viewer-centered perception?
What is the primary function of cones in the retina?
What is the primary function of cones in the retina?
Which Gestalt principle relates to perceiving objects close together as a group?
Which Gestalt principle relates to perceiving objects close together as a group?
Which part of the brain do ganglion cells primarily send signals to after passing through the optic chiasma?
Which part of the brain do ganglion cells primarily send signals to after passing through the optic chiasma?
What is shape constancy?
What is shape constancy?
Where are cones most concentrated in the retina?
Where are cones most concentrated in the retina?
Which system specializes in recognizing parts of objects?
Which system specializes in recognizing parts of objects?
What happens to ganglion cells from the nasal part of the retina at the optic chiasma?
What happens to ganglion cells from the nasal part of the retina at the optic chiasma?
According to bottom-up theories of perception, how does perception begin?
According to bottom-up theories of perception, how does perception begin?
Which theory suggests that all information needed for perception is available in the environment?
Which theory suggests that all information needed for perception is available in the environment?
What aspect of visual information does the primary visual cortex process?
What aspect of visual information does the primary visual cortex process?
What is the role of the optic nerve in vision?
What is the role of the optic nerve in vision?
What are templates in the context of template theories?
What are templates in the context of template theories?
In feature-matching theories, how do we recognize patterns?
In feature-matching theories, how do we recognize patterns?
What do 'feature demons' do in Oliver Selfridge's Pandemonium Model?
What do 'feature demons' do in Oliver Selfridge's Pandemonium Model?
How do recognition by component theories aid in object recognition?
How do recognition by component theories aid in object recognition?
What is a key characteristic of geons in recognition by component theories?
What is a key characteristic of geons in recognition by component theories?
What do top-down theories in perception emphasize?
What do top-down theories in perception emphasize?
What does the concept of 'Constructive Perception' imply?
What does the concept of 'Constructive Perception' imply?
In the process of perception, what are the three main components that influence percept formation?
In the process of perception, what are the three main components that influence percept formation?
What condition is characterized by an impaired ability to recognize human faces?
What condition is characterized by an impaired ability to recognize human faces?
Which type of agnosia involves the inability to pay attention to more than one object at a time?
Which type of agnosia involves the inability to pay attention to more than one object at a time?
What visual deficit arises from damage to the posterior parietal cortex, affecting movement guidance?
What visual deficit arises from damage to the posterior parietal cortex, affecting movement guidance?
Which depth cue is primarily based on the visual perceptual differences between objects as they approach?
Which depth cue is primarily based on the visual perceptual differences between objects as they approach?
What is the only true form of pure color blindness?
What is the only true form of pure color blindness?
Which of the following results in the extreme form of red-green color blindness?
Which of the following results in the extreme form of red-green color blindness?
Which deficit involves individuals who have trouble recognizing what objects are despite their ability to perceive colors and shapes?
Which deficit involves individuals who have trouble recognizing what objects are despite their ability to perceive colors and shapes?
What phenomenon refers to the increased disparity in images sent to the brain as objects approach?
What phenomenon refers to the increased disparity in images sent to the brain as objects approach?
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Study Notes
From Sensation to Perception
- Perception involves recognizing, organizing, and making sense of sensations from environmental stimuli.
- Vision requires light, with the visible spectrum for humans ranging from 380 to 750 nm.
- The eye's cornea protects the external structure, guiding light through the pupil, lens, and vitreous humor to the retina.
- The retina converts light into neural impulses, with the fovea being the region of sharpest vision, containing a high density of photoreceptors.
Photoreceptors
- Rods (approximately 120 million) are responsible for night vision and detect light and dark stimuli, primarily located in the periphery of the retina.
- Cones (about 8 million) enable color perception and are concentrated in the fovea.
Neural Pathway
- Signals from rods and cones are transmitted through bipolar cells to ganglion cells, forming the optic nerve, which connects to the brain.
- At the optic chiasma, some ganglion cell fibers cross to the opposite brain hemisphere.
- Most neural signals (about 90%) transmit to the lateral geniculate nucleus (LGN) of the thalamus before reaching the primary visual cortex (V1).
Perception Approaches
-
Bottom-Up Theories focus on how perception starts with sensory input; examples include:
- Direct Perception: Recognizes that all perceptual information is available in the environment.
- Template Theories: Propose that we store detailed patterns to recognize stimuli.
- Feature-Matching Theories: Involve matching features of stimuli to stored memory features.
- Recognition by Components: Objects recognized by decomposing them into basic geometric shapes (geons).
-
Top-Down Theories highlight the role of cognitive processes, knowledge, and expectations that influence perception.
- Constructive perception emphasizes the active role of the brain in forming perceptions based on experience.
Object and Form Perception
- Viewer-Centered Perception: Changes in perception based on the viewer's position.
- Object-Centered Perception: Recognizes objects as having stable shapes regardless of viewing angle.
- Gestalt Laws describe how we see groups as wholes, governed by principles like proximity, similarity, and closure.
Depth Perception
- Depth Cues help determine distance:
- Monocular cues include texture gradient and relative size.
- Binocular cues involve binocular disparity and convergence.
Perceptual Constancies
- Size Constancy: Perception of consistent object size despite changes in distance.
- Shape Constancy: Perception of consistent object shape despite viewing angle changes.
Deficits in Perception
-
Agnosia: Difficulty in recognizing objects despite normal sensory input, often due to brain damage.
- Simultagnosia: Inability to attend to multiple objects simultaneously.
- Prosopagnosia: Impaired ability to recognize faces.
-
Ataxia: A perceptual deficit impacting the ability to use visual input to guide movements, connected to the posterior parietal cortex.
Color Perception Anomalies
- Color Blindness: Impairments in color vision.
- Achromacy: Complete absence of color vision.
- Dichromacy: Only two color perception mechanisms are functioning; includes:
- Protanopia: A form of red-green color blindness.
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