8 Perceiving Motion and Events

Question 1

Q: Why is motion perception considered evolutionarily important?

Answer 1

A: Motion perception evolved very early, playing a crucial role in survival and reproduction by helping organisms detect food, predators, and navigate their environment.

Question 2

Q: How does motion perception benefit predators?

Answer 2

A: Predators that can detect motion are more effective hunters, increasing their likelihood of catching prey.

Question 3

Q: How does motion perception benefit prey animals?

Answer 3

A: Prey animals that can detect motion are better at evading predators, enhancing their chances of survival.

Question 4

Q: What is a common visual ability across all animals?

Answer 4

A: All animals have the ability to perceive motion, even if they have poor depth, shape, or color perception.

Question 5

Q: Why else is the function of motion?

Answer 5

• 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

Question 6

Q: Do we need to recognize an object in order to see it move?

Answer 6

A: No, we do not need to recognize an object to see it move. Motion perception can occur independently of object recognition.

Question 7

Q: Do we match edges and contours between successive views of an object to perceive motion?

Answer 7

A: No, random dot kinematograms suggest that motion perception does not rely on matching edges and contours between successive views.

Question 8

Q: What do random dot kinematograms demonstrate about motion perception?

Answer 8

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.

Question 9

Q: How do random dot kinematograms work in experiments on motion perception?

Answer 9

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.

Question 10

Q: What is the correspondence problem in motion perception?

Answer 10

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.

Question 11

Q: What do findings from random dot kinematogram studies suggest about our visual system?

Answer 11

A: These findings suggest that our visual system perceives motion directly rather than through detailed matching of points or contours between successive frames.

Question 12

Q: How do we perceive movement when our eyes are stationary?

Answer 12

A: We perceive movement because the image moves across the retina, stimulating a series of receptors.

Question 13

Q: What do neurons in the visual system respond to regarding movement?

Answer 13

A: Neurons respond best when a stimulus moves in a particular direction, such as from right to left.

Question 14

Q: How do movement detectors work in the visual system?

Answer 14

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.

Question 15

Q: How can the direction and speed of detected motion be altered?

Answer 15

A: Changing the order of signal delay changes direction, while altering the spacing of detectors changes speed.

Question 16

Q: Where are movement detectors found?

Answer 16

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.

Question 17

Q: What is the aperture problem in motion perception?

Answer 17

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.

Question 18

Q: What did studies on monkeys reveal about neurons in the medial temporal (MT) area?

Answer 18

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.

Question 19

Q: What factors influence the threshold for perceiving movement?

Answer 19

A: The threshold for movement detection depends on the object and its surroundings, with increased background context lowering the threshold.

Question 20

Q: What affects the perception of velocity?

Answer 20

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.

Question 21

Q: When do we not experience movement perception?

Answer 21

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.

Question 22

Q: What mechanism helps differentiate between stimulus movement, observer movement, or both?

Answer 22

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.

Question 23

Q: What evidence supports Helmholtz’s outflow theory?

Answer 23

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).

Question 24

Q: What is apparent movement?

Answer 24

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.

Question 25

Q: How is the perception of movement in films created?

Answer 25

A: The perception of movement in films is created by showing a series of static images in quick succession.

Question 26

Q: According to Graham (1965), what happens when the time interval between flashes is less than 30ms?

Answer 26

A: When the time interval is less than 30ms, there is no perception of movement; the lights are seen as simultaneous.

Question 27

Q: What is perceived when the time interval between flashes is 30-60ms?

Answer 27

A: When the time interval is 30-60ms, partial movement is perceived.

Question 28

Q: What is the optimum time interval for perceiving movement between flashes?

Answer 28

A: The optimum time interval for perceiving movement is around 60ms.

Question 29

Q: What are beta and phi movements, and at what time interval do they occur?

Answer 29

A: Beta and phi movements occur at 60-200ms. Beta movement is when it seems there is movement between the lights, but no object is seen moving. Phi movement is when an object is perceived moving between the lights.

Question 30

Q: What happens when the time interval between flashes is above 200ms?

Answer 30

A: When the time interval is above 200ms, no movement is perceived; the lights are seen as successive.

Question 31

Q: How does the distance between two lights affect the perception of apparent movement?

Answer 31

A: As the distance between two lights increases, the time interval or intensity of the flashes must increase to maintain the same perception of movement.

Question 32

Q: What is induced movement?

Answer 32

A: Induced movement is the illusion of movement experienced when a surrounding object moves, making a stationary object appear to move.

Question 33

Q: Can you give an example of induced movement?

Answer 33

A: An example of induced movement is when a train passes by your stationary train, creating the illusion that your train is moving backward.

Question 34

Q: What is autokinetic movement?

Answer 34

A: Autokinetic movement is the illusion where a small stationary light appears to move in a dark room when the surrounding framework is not visible.

Question 35

Q: What did Sherif’s 1935 study on autokinetic movement find about individual reports?

Answer 35

A: Individually, participants reported that the dot moved between 0.8 to 7.4 inches.

Question 36

Q: What did Sherif’s 1935 study find when participants were in a group?

Answer 36

A: When in a group, participants reported that the dot moved about 4 inches, demonstrating that the autokinetic effect is open to suggestion.

Question 37

Q: What does the autokinetic effect suggest about eye muscle control in the dark?

Answer 37

A: The autokinetic effect suggests that control of eye muscles may not be completely stable in the dark, making it difficult to know where the eyes are and how stable they are.

Question 38

Q: How can suggestion influence the autokinetic effect?

Answer 38

A: Suggestion can influence the perceived movement of the light, as people tend to conform to a group norm or suggestion in their reports of how much the light moves.

Question 39

Q: What historical phenomenon is associated with the autokinetic effect?

Answer 39

A: “Foo fighters,” unexplained aerial phenomena reported by pilots during World War II, are associated with the autokinetic effect.

Question 40

Q: What are movement after-effects?

Answer 40

A: Movement after-effects occur when an observer first views a pattern moving in one direction and then views a stationary spot, which then appears to move in the opposite direction.

Question 41

Q: What is the waterfall illusion?

Answer 41

A: The waterfall illusion is a specific type of movement after-effect where, after staring at a waterfall moving downward, stationary objects (like rocks) appear to move upward.

Question 42

Q: What did Anstis and Gregory (1964) find about the waterfall illusion?

Answer 42

A: They found that the illusion depends on the movement of stripes across the retina, supporting the idea of movement detectors that respond to movement across the retina.

Question 43

Q: What is the ratio hypothesis in the context of motion after-effects?

Answer 43

A: The ratio hypothesis suggests that motion after-effects arise from an imbalance in the ratio of activities from two sets of directionally-tuned receptors, each sensitive to opposite directions of motion.

Question 44

Q: Who identified directionally specific motion detectors and when?

Answer 44

A: Hubel and Wiesel identified directionally specific motion detectors in 1959.

Question 45

Q: Who proposed the ratio hypothesis and when?

Answer 45

A: Sutherland proposed the ratio hypothesis in 1961.

Question 46

Q: What evidence supports the ratio hypothesis?

Answer 46

A: Barlow and Hill (1963) provided evidence supporting the ratio hypothesis.

Question 47

Q: How does event perception relate to movement?

Answer 47

A: Movement provides information about the 3D shape of objects, helps segregate figure from ground, and allows us to interact with the environment, such as creating structure from motion.