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Psyc 212 - Perception > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

Akinetopsia

A

“Motion blindness”; Condition in which perceiving motion is extremely difficult or even impossible

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2
Q

Who was the most famous case of akinetopsia and how did they perceive motion?

A

Most famous case was L.M., a 43 year old woman who lost her ability to perceive motion following a stroke; she viewed moving objects and people as STATIC, disappearing and reappearing as they approached her or simply still

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3
Q

Why is detection critical for survival

A

SAFETY: Detecting an objects moving in our direction (or in older times, an animal running or jumping in our direction) is crucial for preserving our safety

EVERYDAY TASKS

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4
Q

Event

A

A segment of time at a particular location that is perceived by observers to have a beginning and an end

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5
Q

Event boundary

A

The point in time when each of these events ENDS and the next one BEGINS

Event boundaries are often associated with changes in the NATURE OF MOTION (first you order coffee, that’s one boundary, then you pay the tab, that’s a second boundary, and so on)

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6
Q

Why is motion important for perceiving events?

A

Different types of motion helps separate activities into meaningful events

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7
Q

Point-Light Walkers

A

A form of presenting/illustrating human motion that consists of placing small lights on people’s joints and then filming the patterns created by these lights when people move

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8
Q

Why do researchers use point-light walkers in experiments regarding movement?

A

Point-light walkers allow experiments to follow movement WITHOUT the social cues usually present in social interactions

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9
Q

How is motion significant for social perception?

A

Many social cues are available in person-to-person interactions THROUGH perceiving the small types of motion someone displays, like facial expressions, posture and more

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10
Q

Atesh Koul and Co. Experiment

A

Demonstrated that the SPEED AND TIMING of a movement can help people distinguish the meaning/purpose behind seemingly identical types of movement (like waving at someone versus swatting at a fly)

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11
Q

True/false: Characteristics of movement can be used to interpret EMOTIONS

A

True

In an experiment by Fritz Heider and Marianne Simmel, participants were shown a short animated film made up of GEOMETRIC SHAPES, and were later asked to describe what happened in the movie; participants described the shapes in the film with HUMAN-LIKE characteristics and story plots, assigning emotions and behaviors correspondent to these emotions to the geometric shapes

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12
Q

Real Motion

A

When something or someone moves across our field of view

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13
Q

Illusory Movement

A

The perception of the motion of stimuli that AREN’T actually moving

Types:
Apparent Motion
Induced Motion
Illusory Motion
Motion Afteteffects

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14
Q

Apparent Motion

A

Most famous type of ILLUSORY MOTION that consists of two stimuli in slightly different locations that are alternated with a SPECIFIC TIMING, generating the illusion of back and fo in rth movement

Is the basis for motion we perceive in movies, TV and moving signs

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15
Q

Induced Motion

A

An illusion of visual perception in which a stationary or a moving object appears to move or to move differently because of other moving objects nearby in the visual field

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16
Q

Illusory Motion

A

that occurs when motion of ONE object (usually a large one) causes a nearby stationary object (usually smaller than the first) to APPEAR to move

Ex: When clouds are moving past the moon, it may appear like the moon is “racing” through the clouds

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17
Q

Motion Aftereffects

A

Type of ILLUSORY MOTION that occurs when viewing a MOVING STIMULUS causes another STATIONARY STIMULUS TO APPEAR moving as well

Ex: Waterfall Illusion

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18
Q

Waterfall Illusion

A

An example of a MOTION AFTEREFFECT, in which staring at a waterfall for 30-60 seconds, then looking off to the rest of the scenery leads EVERYTHING ELSE to appear moving upward for a few seconds

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19
Q

The Ecological Approach to Motion Perception

A

According to Gibson perception is largely involves and depends on looking for information in the environment; this information can be determined in terms of the OPTIC ARRAY: The STRUCTURE created by the surfaces, textures and contours of the environment

Movement of the observer causes CHANGES in the optic array

These changes are termed LOCAL DISTURBANCES: A “Disturbance” that occurs in the optic array when a person or object moves relative to the environment, covering and uncovering the stationary background; IT IS CHANGE IN “POSITION” AND BACKGROUND THAT REFLECTS ON THE RETINA AND ALLOWS US TO PERCEIVE MOTION

20
Q

Global Optic Flow

A

The fact that everything moves at once when the observer’s EYES OR BODY moves (shifting to a different direction or moving in of itself)

21
Q

What does Global Optic Flow have to do with the Ecological Approach to Percpetion

A

According to Gibson, motion is perceived when ONE PART of the visual scene moves RELATIVE to the rest of the scene, and NO MOTION is perceived when the entire field moves or remains stationary

22
Q

The Corollary Discharge to Motion Perception

A

COROLLARY DISCHARGE THEORY: Theory that states that movement will be perceived if a brain structure called the COMPARATOR receives just ONE signal, EITHER the IMAGE DISPLACEMENT SIGNAL or the COROLLARY DISCHARGE SIGNAL; NO MOVEMENT will be perceived if the comparator receives both signals at the same time

23
Q

Comparator

A

A series of different brain structures that has a mechanism that takes into account BOTH information about stimulation of the receptors and information about movement of the eyes

24
Q

Image Displacement Theory

A

Signal that occurs when an image moves across the retina

25
Q

Motor signal

A

Signal sent from the MOTOR AREA to the eye muscles to cause the eye to move

26
Q

Corollary Discharge Signal

A

A copy of the motor signal that is originally sent to from the brain to the eye muscles, and that thus occurs whenever there is a motor signal

Is why we don’t see the scene blur when we move our eye from place to place when scanning a scene

27
Q

Describe an illustration of the IDT signal versus the Corollary Signal

A

When an observer is standing still watching a stimulus move, there is a IDT signal, but no corollary signal, and when the observe is glancing up and down, there is a corollary signal but not IDT signal

28
Q

Reichardt Detector

A

Neural circuit proposed by Werner Reichardt, which consists of two neurons (neuron A and neuron B), which send their signals to an OUTPUT UNIT that compares the signals it receives from both neurons. The key to the operation of the circuit is a DELAY UNIT that slows down the signals from neuron A as they travel towards the output unit; the OUTPUT unit is then able to MULTIPLY the responses from A and B to create the movement signal that results in the perception of motion

Circuit’s neurons are DIRECTIONALLY SENSITIVE, only resulting in a signal if the neurons are stimulated in a specific order (as a stimulus is moving in a specific direction)

The visual system contains many circuits like this, EACH TUNED TO A DIFFERENT DIRECTION OF MOTION

29
Q

Middle Temporal (MT) Area

A

Area in the lateral surface of the temporal lobe, which contains many directionally selective neurons

30
Q

Coherence

A

Term that indicates the degree to which dots in a display move in the same direction

31
Q

What did William Newsome note about COHERENCE through moving dot displays?

A

In monkeys, William Newsome noticed that COHERENCE was directly correlated to the firing of MT neurons, and to the monkey’s consequent ability to judge the overall direction of the dots

He concluded that as the dots’ coherence increased, (1) A monkey’s ability to judge the direction in which dots were moving, and (2) the MT fired more vigorously

32
Q

Transcranial Magnetic Stimulation

A

An experimental method used to study the MT cortex in humans that temporarily disrupts the normal functioning of neurons by applying a strong magnetic field using a stimulating coil placed over a person’s skull

If a particular behavior is disrupted by the electromagnetic pulses applied to a particular area of the brain then researchers conclude the disrupted area is involved in the behavior

33
Q

Microstimulation

A

Experimental technique achieved by lowering a small wire electrode into the cortex and passing a weak electrical charge through the tip of the electrode; this weak shock stimulates neurons that are near the electrode, causing them to fire. The experimenters then locate the neurons that would typically respond to certain stimuli

34
Q

Aperture Problem

A

refers to the fact that the motion of a one-dimensional spatial structure, such as a bar or edge, cannot be determined unambiguously if it is viewed through a small aperture such that the ends of the stimulus are not visible (view picture in page 186/187)

It isn’t possible to know which side exactly a stimulus is moving merely based on the activity of a single neuron, because its field of view is too small/limited

35
Q

What are solutions to the Aperture Problem?

A

1) A neuron could use information about the END OF AN OBJECT (like the tip of a pencil) to determine the overall direction of motion

2) Neurons can also simply POOL/COMBINE TOGETHER INFORMATION from a number of neurons

36
Q

Shortest Path Constraint

A

Apparent (illusory) movement that occurs between two stationary stimuli in apparent motion, that TENDS TO OCCUR ALONG THE SHORTEST PATH BETWEEN TWO STIMULI

37
Q

Maggie Schiffrar and Jennifer Freyd Experiment

A

Found that when they presented two pictures in very quick consecutive order (of a woman clapping in front of her face and then behind her head) the SHORTEST PATH CONSTRAINT made it so that people saw the woman’s hands as moving THROUGH HER head; when the images were slowed down eventually participants were able to see the individual hand movements

38
Q

True/False: Both the MOTOR and PARIETAL CORTEX(es) activate whenever we see ANY kind of motion

A

False

When we see movement coming from a HUMAN (or possibly being human), the BOTH the MOTOR CORTEX and the PARIETAL CORTEX activate

When movements are not deemed possibly human, ONLY the parietal cortex shows activity

39
Q

Biological Motion

A

Self-produced motion of a person or other living organism

40
Q

What is the typical “biological motion” of humans

A

Two sorts of “arms” and “legs” swinging back and forth and feet moving in flattened arcs, with one foot leaving the ground at a time

41
Q

Which brain area is specialized in reaction to biological motion?

A

Superior Temporal Sulcus (STS)

42
Q

Implied Motion

A

Situation in which a still picture depicts an action involving motion

43
Q

Representational Momentum

A

Idea/effect that the motion depicted in a picture tends to continue in the observer’s mind (effect is influenced by our knowledge of previous experiences)

Ex: If we see a picture of a person mid-back flip we mentally imagine them completing the flip

44
Q

How did Jennifer Freyd “prove” Representational Momentum?

A

Freyd tested implied motion by showing participants a picture of a person midair, and then a few seconds later showing them one of three pictures: the same picture, a picture slightly forward in time, a picture slightly backwards in time, and asked them to tell her if the second picture was the same as the first

PARTICIPANTS TOOK LONGER TO DECIDE IF THE TIME-FORWARD PICTURE WAS THE SAME OR DIFFERENT COMPARED TO THE OTHER OPTIONS

Freyd concluded people have TIME-FORWARD ANTICIPATION when it comes to implied motion, in which seeing an image of an action already makes us predict the immediate motion that will follow the one frozen on the image

45
Q

True/false: the part of the brain that reacts to actual motion also responds to PICTURES of motion

A

True

46
Q

What are the experimental techniques for studying the MT Cortex?

A

Transcranial Magnetic Stimulation

Microstimulation

47
Q

What are some things that detecting motion helps us perceive?

A

Objects
Meaningful events
Social cues and interaction “rules”
How to coordinate our own behavior in relation to others (how to act)

Psyc 212 - Perception (6 decks)

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