Attention and perception part 2 unit 9 Flashcards
What sources of information allow us to perceive depth and size?
Environmental information: Includes cues from light, shadows, and other visual details in the surroundings.
Physical sensations: Arise from eye movements and adjustments (e.g., muscle tension when focusing on near vs. far objects).
Why is perceiving depth from a 2D retinal image challenging?
A single retinal image doesn’t inherently contain depth information; it represents the world in two dimensions. The brain must process and interpret this flat image to reconstruct a 3D perception of objects’ distances and locations.
What is the cue approach to studying depth perception?
It examines information in the retinal image that provides cues about object depth.
How does experience influence our use of depth cues?
With repeated exposure, we learn to associate certain visual patterns with depth. For instance, overlapping objects suggest one is closer than the other, and this understanding becomes automatic over time.
What are the three main types of depth cues?
Oculomotor cues – Based on eye position and muscle tension.
Monocular cues – Use visual information from one eye.
Binocular cues – Use visual information from both eyes.
What are oculomotor cues?
Depth cues based on the sensations we feel from the movements of our eyes and the tension in the muscles controlling them. These cues are especially useful for detecting depth at close distances.
What is convergence, and how does it provide depth information?
A:
Convergence is the inward movement of the eyes when focusing on nearby objects.
The convergence angle (the angle at which both eyes align on the object) changes with the distance:
Closer objects require more inward eye movement, creating stronger physical sensations.
These sensations are processed by the nervous system to calculate the object’s distance.
How does accommodation contribute to depth perception?
Accommodation refers to changes in the shape of the eye’s lens to focus on objects at different distances:
For closer objects, the lens becomes thicker.
For distant objects, the lens flattens.
The ciliary muscles controlling these changes produce tension, which the nervous system interprets as depth information.
Between convergence and accommodation, which provides stronger depth information?
Convergence provides stronger depth cues than accommodation because it produces more pronounced physical sensations.
Both cues are most effective for objects located within an arm’s length.
Why are oculomotor cues limited in detecting distant objects?
The physical sensations from convergence and accommodation become less noticeable as the distance increases.
For objects further than an arm’s length, we rely on other cues like monocular and binocular cues for depth perception.
What are monocular cues?
Depth cues that can be obtained using just one eye. They include pictorial cues (depth information from still images) and motion cues (depth information from movement).
What is occlusion, and how does it provide depth information?
Occlusion occurs when one object blocks another from view.
The object doing the blocking is perceived as closer, while the partially or fully hidden object is seen as further away.
Occlusion provides relative distance but not precise measurements of how far apart objects are.
How does relative height inform depth perception?
Objects higher in the visual field (closer to the horizon) are generally perceived as further away.
However, this reverses for objects above the horizon: higher objects appear closer, and lower ones appear further away.
Your horizon line is the key reference:
Above the horizon: Higher objects seem farther away.
Below the horizon: Lower objects closer to the horizon seem farther away.
What is the role of familiar size in depth perception?
Familiar size relies on prior knowledge of an object’s typical size to judge distance.
Example: If two coins of known sizes appear the same on the retina, the smaller coin (e.g., 1 cent) is judged to be closer than the larger coin (e.g., 50 cents).
How does relative size work as a depth cue?
When two objects are known to be of equal size, the smaller object in the retinal image is perceived as further away.
Larger objects in the visual field are interpreted as closer.
What is perspective convergence, and how does it aid depth perception?
Parallel lines appear to converge as they recede into the distance (e.g., railway tracks).
The point of convergence indicates greater distance, helping us perceive depth in 2D images.
Converging lines towards a point in a 2D image produces the perception that objects closer to the point of convergence are more distant than objects further from the point of convergence
How does atmospheric perspective contribute to depth perception?
Distant objects appear less sharp and slightly blue-tinted due to particles (dust, water, air) scattering light.
This cue helps judge objects at far distances.
What is a texture gradient, and what information does it provide?
A texture gradient occurs when equally spaced objects appear closer together as they recede into the distance.
This gradual change in texture helps us perceive depth.
A texture gradient happens when objects or patterns that are equally spaced appear closer together as they get farther away from you.
making closer objects appear larger and more spread out, while distant ones look smaller and denser
How do shadows inform depth perception?
Shadows provide clues about an object’s position relative to a surface (e.g., resting or hovering).
They also reveal the three-dimensional shape of objects (e.g., spheres appearing round due to shading).
Shadows create depth and make objects appear more three-dimensional instead of flat.
What are motion cues, and how do they differ from pictorial cues?
Motion cues are depth cues derived from movement, either of the observer or objects in the environment.
Unlike pictorial cues, they require changes over time to infer depth and distance.
What is motion parallax, and how does it create depth perception?
Motion parallax occurs when nearby objects move faster across the visual field than distant objects as you move.
Example: When looking out of a car window, trees near the road seem to move faster than distant mountains.
Why do close and distant objects move at different speeds during motion parallax?
The retinal image of closer objects shifts across a larger distance in the same period compared to distant objects.
Greater speed is associated with closer objects.
What are deletion and accretion, and how do they provide depth information?
Deletion: Occurs when an object is covered as you or other objects move.
Accretion: Occurs when an object is uncovered during movement.
These effects help determine relative distances between objects.
How can you experience deletion and accretion yourself?
Hold one hand at arm’s length and the other closer to your face.
Move your head side to side: the closer hand will alternately cover (deletion) and uncover (accretion) the further hand, providing depth information.
