8 Perceiving Motion and Events Flashcards
(47 cards)
Q: Why is motion perception considered evolutionarily important?
A: Motion perception evolved very early, playing a crucial role in survival and reproduction by helping organisms detect food, predators, and navigate their environment.
Q: How does motion perception benefit predators?
A: Predators that can detect motion are more effective hunters, increasing their likelihood of catching prey.
Q: How does motion perception benefit prey animals?
A: Prey animals that can detect motion are better at evading predators, enhancing their chances of survival.
Q: What is a common visual ability across all animals?
A: All animals have the ability to perceive motion, even if they have poor depth, shape, or color perception.
Q: Why else is the function of motion?
- Attracts our attention
- Provides info about 3D object
- Provides info that segregates figure from ground + perceptual organisation
- Breaks camoflauge
Provides info allowing us to actively interact w/ environment, eg ball games - Informs of your heading + time to collision, your movement + other objects
Q: Do we need to recognize an object in order to see it move?
A: No, we do not need to recognize an object to see it move. Motion perception can occur independently of object recognition.
Q: Do we match edges and contours between successive views of an object to perceive motion?
A: No, random dot kinematograms suggest that motion perception does not rely on matching edges and contours between successive views.
Q: What do random dot kinematograms demonstrate about motion perception?
A: Random dot kinematograms demonstrate that motion can be perceived even when individual frames do not contain recognizable shapes, suggesting that motion perception is direct and does not rely on recognizing form.
Q: How do random dot kinematograms work in experiments on motion perception?
A: In these experiments, a first frame is presented followed by a second frame after a short delay. Observers perceive a central square moving even though no square is recognizable in either frame alone.
Q: What is the correspondence problem in motion perception?
A: The correspondence problem refers to the challenge of determining which points in one frame correspond to which points in the next frame. This problem suggests that motion perception is direct and does not involve point-by-point matching over time.
Q: What do findings from random dot kinematogram studies suggest about our visual system?
A: These findings suggest that our visual system perceives motion directly rather than through detailed matching of points or contours between successive frames.
Q: How do we perceive movement when our eyes are stationary?
A: We perceive movement because the image moves across the retina, stimulating a series of receptors.
Q: What do neurons in the visual system respond to regarding movement?
A: Neurons respond best when a stimulus moves in a particular direction, such as from right to left.
Q: How do movement detectors work in the visual system?
A: Movement detectors respond to specific directions and speeds. Signals that meet at the right time create a strong response; wrong direction or speed results in no response.
Q: How can the direction and speed of detected motion be altered?
A: Changing the order of signal delay changes direction, while altering the spacing of detectors changes speed.
Q: Where are movement detectors found?
A: These detectors are found in insects and frogs, and similar cells are present in the human cortex, sensitive to different orientations, speeds, and directions of movement.
Q: What is the aperture problem in motion perception?
A: The aperture problem occurs when the output of all motion detectors must be integrated to perceive motion correctly, typically in the medial temporal area.
Q: What did studies on monkeys reveal about neurons in the medial temporal (MT) area?
A: As the correlated movement of random dots increased, MT neurons fired more. Monkeys could indicate direction by pressing a button, and stimulation of MT neurons caused the monkeys to press the button even without visual stimuli.
Q: What factors influence the threshold for perceiving movement?
A: The threshold for movement detection depends on the object and its surroundings, with increased background context lowering the threshold.
Q: What affects the perception of velocity?
A: Perception of velocity is affected by the surroundings, the size of the moving object, and the framework through which it moves. For example, a longer framework requires the object to move twice as fast to appear at the same speed.
Q: When do we not experience movement perception?
A: We do not perceive movement when there’s no movement on the retina, such as when following an object with our eyes, or when we perceive no movement despite retinal movement.
Q: What mechanism helps differentiate between stimulus movement, observer movement, or both?
A: Helmholtz’s outflow theory helps by comparing the efferent signal (eye muscle commands) and the afferent signal (retinal movement). If they cancel out, no movement is perceived; if there’s a mismatch, motion is perceived.
Q: What evidence supports Helmholtz’s outflow theory?
A: - Afterimages move when we move our eyes (eye movement signal, no retinal movement).
The world moves when we passively wobble our eyes (retinal movement, no eye movement signal).
Immobilizing the eye leads to perceived movement of the world in the opposite direction when attempting eye movement (eye movement signal, no retinal movement).
Q: What is apparent movement?
A: Apparent movement is the illusion of movement between two lights by flashing one on and off, waiting 10-200ms, then flashing the other on and off.
