Psychophysics Quiz: Methods and JND

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Questions and Answers

What does the Just-Noticeable-Difference (JND) represent?

The average intensity of all presented stimuli.

The smallest difference in stimulus strength needed to discriminate two stimuli. (correct)

The point at which a participant can no longer detect a stimulus.

The maximum stimulus strength that can be detected.

Which law indicates that the JND changes as the intensity of the stimulus changes, yet maintains a constant proportion?

Constant Stimuli Method

Weber's Law (correct)

Stevens' Law

Fechner's Law

Which method involves presenting a fixed set of stimulus strengths in random order to categorize detectable stimulus strengths?

Limits Method

Constant Stimuli Method (correct)

Adjustment Method

Threshold Method

How does Stevens' Law differ from Weber's and Fechner's laws?

It uses a flexible exponent to capture different sensory dimensions. Signup and view all the answers

What is the main limitation of both Weber's and Fechner's laws regarding perception?

They struggle with cases where perceived intensity exceeds physical change. Signup and view all the answers

Which of the following best describes the phenomenon of compression in sensory perception?

Decreased sensitivity to change as stimulus strength increases. Signup and view all the answers

In the limits method of detecting light, what is the primary action taken by the researcher?

Adjust stimulus strength based on participant's detection threshold. Signup and view all the answers

What is the result of averaging the intensity where a participant's response changes in the adjustment method?

The detection threshold. Signup and view all the answers

Which aspect of color vision relates to the purity of wavelengths in light?

Saturation Signup and view all the answers

What type of color mixing occurs when different wavelengths of light are added together?

Additive color mixing Signup and view all the answers

Which statement best describes simultaneous color contrast?

It is when colors look different depending on their background. Signup and view all the answers

Which of the following is NOT a function of color vision?

Enhancing auditory perception Signup and view all the answers

What typically happens when combining pigments in color mixing?

More wavelengths are absorbed. Signup and view all the answers

Hue is primarily associated with what property of light?

Wavelength Signup and view all the answers

What does the fruit theory suggest about the evolution of color vision?

It evolved to help detect ripe fruit. Signup and view all the answers

Which statement is true regarding brightness in color perception?

More reflected light results in a brighter color. Signup and view all the answers

Which color deficiency prevents individuals from perceiving red?

Protanopia Signup and view all the answers

What do nonspectal hues refer to?

Colors perceived without a specific wavelength Signup and view all the answers

Which theory supports the idea that color perception is based on three primary colors?

Trichromatic theory Signup and view all the answers

What phenomenon occurs after staring at a red object for a prolonged period?

Color afterimage Signup and view all the answers

What is the main shortcoming of the trichromatic theory?

It fails to explain colorblindness phenomena. Signup and view all the answers

Which cone is lacking in individuals with tritanopia?

S cone Signup and view all the answers

How is yellow perceived, according to trichromatic theory?

As a mixture of red and green Signup and view all the answers

What does the term 'successive contrast' refer to in color perception?

The effect of viewing a color before seeing its complement Signup and view all the answers

What is the primary function of edge detection in visual perception?

To identify the boundaries of objects Signup and view all the answers

What type of junction is formed when one object partially blocks another?

T junction Signup and view all the answers

Which of the following is NOT a challenge to edge detection?

Recognizing 3D object corners Signup and view all the answers

What is the main idea behind Gestalt theory?

The whole is greater than the sum of its parts. Signup and view all the answers

Which property of Gestalt theory refers to the perception of objects having more spatial information than the stimuli they are based on?

Reification Signup and view all the answers

What do we call the process of deciding what goes together in a visual scene?

Segmentation and grouping Signup and view all the answers

Which type of edge is often challenging to detect due to low or no contrast?

Occluded edges Signup and view all the answers

What does the term 'multistability' refer to in the context of Gestalt psychology?

The perception of ambiguous stimuli having multiple interpretations. Signup and view all the answers

What type of colorblindness is the most common?

Red-green color blindness Signup and view all the answers

How does the opponent-process theory explain the phenomenon of seeing a green afterimage after viewing red?

Red light excites an opponent process that inhibits perception of green. Signup and view all the answers

Which two colors are paired as opposites in opponent-process theory?

Red and green Signup and view all the answers

What is one of the major problems with trichromatic theory as highlighted by opponent-process theory?

It does not account for the distinct sensations of yellow. Signup and view all the answers

What happens to the perception of one color when its opponent color is perceived, according to opponent-process theory?

The perception of the first color is inhibited. Signup and view all the answers

In the context of color vision theories, what does 'successive contrast' refer to?

The phenomenon of seeing a color after its presence has ceased. Signup and view all the answers

According to opponent-process theory, what coding principle is used to explain color perception issues in red-green colorblindness?

Colors are coded as opposing perceptions. Signup and view all the answers

What aspect of perception does the opponent-process theory challenge from the trichromatic theory?

The idea that yellow is not a primary color. Signup and view all the answers

Study Notes

Psychophysical Methods

Constant Stimuli uses predetermined stimulus strengths in random order to determine a participant's perception.
- The intensity that corresponds to a 50% chance of accuracy is found by fitting responses to a curve.
Limits involve starting with a strong or weak stimulus and gradually increasing or decreasing it until the participant can no longer detect it.
- The average intensity where the participant's response changes is used.
Adjustment lets the participant control the stimulus strength until it is visible or not visible.
- The average point of change in the participant's responses is recorded.

Just Noticeable Difference (JND)

JND: The smallest difference in stimulus strength needed to distinguish between two stimuli.
Weber's Law: JND changes with stimulus intensity, but the proportion remains constant.
- JND gets larger as intensity increases, meaning we become less sensitive to changes at higher intensities.
Fechner's Law: A revision of Weber's Law that measures sensory magnitude.
- Shows that sensitivity to change decreases as stimulus strength increases.
Steven's Law: More flexible relationship than Weber's and Fechner's laws, capturing cases where perception is directly proportional or greater than physical change.

Psychological Dimensions Of Light

Hue: Related to wavelength, but not always directly.
Brightness: Determined by the amount of light reflected.
- More reflected light results in a brighter color.
Saturation: Represents the purity of the wavelengths of light.
- Colors with more white have multiple wavelengths, resulting in less saturation.

Functions Of Color Vision

Fruit Theory: Proposed that color vision evolved to help us detect ripe fruit.
Object Recognition and Identification: Colors aid in recognizing and identifying objects in space.

Phenomena In Color & Color Vision

Color Mixing:
- Additive color mixing (light): Combining different wavelengths results in white light.
- Subtractive color mixing (pigments): Pigments absorb light, reflecting the color they represent. Combining pigments leads to increased absorption and a darkening effect.
Color Contrast:
- Simultaneous contrast: Same color perceived differently based on background color.
- Successive contrast (color afterimages): Viewing a color for an extended period results in an inverse afterimage.
Color Intuition: Specific color combinations feel natural and intuitive, while others do not.
Color Blindness: Vision without three different cone types (trichromacy).
- Red-green color deficiencies: Most common, caused by a lack of the L-cone (red) or M-cone (green).
- Yellow-blue color blindness: Tritanopia, caused by a lack of the S-cone (blue).

Theories Of Color Vision

Trichromatic Theory (Young-Helmholtz Theory): Color vision relies on three primary color sensations (red, green, blue).
- Supported by the discovery of cones and color-matching experiments.
Opponent-Process Theory (Hering Theory): Color vision is the product of three opponent systems (red-green, blue-yellow, black-white).
- Four primary color perceptions (red, green, yellow, blue) organized into opponent pairs.
- Activating one color in a pair inhibits the perception of the other.

Edge Detection

Edges: Regions of contrast (color, brightness, spatial frequency, etc.) marking object boundaries.
Challenges to edge detection:
- Integrating local edges into global contours.
- Differentiating between true object boundaries and other edge features.
Junctions: Intersections of edges, providing information about edge relationships in space.
- T Junctions: One object occluding another.
- X Junction: Transparent object occlusion.
- L Junction: Corners.
- Y Junction: 3D object corners.
Boundary Detection: Uses edges to separate objects from their background.

Form & Object Perception

The process of combining parts to create an object, even in cases where sections are separate.

Segmenting & Grouping

Processes that identify separate and connected objects in a visual scene.
Gestalt Principles: Classical approach to segmenting and grouping objects.

Gestalt Theory

"The whole is greater than the sum of its parts."
Humans naturally organize visual information into meaningful wholes.
Properties:
- Reification: Perceived object has more spatial information than the sensory stimulus.
- Multistability: Ambiguous stimuli can have multiple interpretations.
- Invariance: Recognition of objects regardless of orientation or position.

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Description

Test your understanding of psychophysical methods such as Constant Stimuli, Limits, and Adjustment. This quiz also explores the concept of Just Noticeable Difference (JND) and Weber's Law. Assess your grasp of how these principles apply to perception.