PS 280: Sensation & Perception Exam 2 Review

Recognizing Visual Objects (Chapter 4)

• Object's Form

  • Refers to the specific shape and structure of an object.
  • Importance: Understanding an object's form is vital for visual perception, as it helps in identifying and differentiating objects in complex visual environments.

• Spatial Scale

  • Defining spatial scale involves understanding how fine (detailed) and gross (broad) scale information contributes to image analysis.
  • Fine spatial scale: Details like edges and textures.
  • Gross spatial scale: Overall shape and arrangement.

• Multichannel Model

  • A theoretical framework that posits multiple channels in processing form perception.
  • Importance: It helps explain how the visual system combines information from different sources to create a cohesive perception of form.

• Grating and Its Characteristics

  • A grating refers to a series of alternating light and dark bars.
  • Characteristics:
  1. Frequency: How many bars are perceived in a given space.
  2. Orientation: The angle of the bars can impact perception.
  3. Contrast: The difference in luminance between the light and dark bars, which affects visibility.

• Contrast Sensitivity Function (CSF)

  • Defines the ability to detect differences in luminance.
  • Relationship with vision types:
  • Photopic (daylight) vision has higher contrast sensitivity than scotopic (low light) vision.

• Pattern Vision Alterations

  • Influenced by natural conditions and selective adaptation.
  • Examples include visual fatigue or temporary changes in perception due to exposure to certain patterns.

• Gestalt Movement

  • A school of thought emphasizing that humans perceive entire objects rather than individual components.
  • Relevant principles include:
  • Proximity: Objects close together are perceived as a group.
  • Similarity: Similar elements are grouped together.
  • Closure: The mind fills in gaps to see complete forms.

• Theories of Object Recognition

  • Two primary theories discussed:
  1. Template Matching Theory: Proposes that objects are recognized by comparing to stored templates of known objects.
  2. Feature Detection Theory: Suggests recognition occurs through detecting specific features and combining them into a perception.

• Inferotemporal Cortex (IT)

  • Location: Found in the temporal lobe of the brain.
  • Function: Involved in higher visual processing and object recognition.
  • Plasticity: Neurons in the IT cortex can adapt based on experience; for example, they may change in response to visual training.

• Prosopagnosia

  • A condition characterized by the inability to recognize faces.
  • Symptoms: Difficulty identifying familiar faces despite normal vision.
  • Associated brain regions include the fusiform gyrus.

Perceiving Color (Chapter 5)

• Color as a Psychological Phenomenon

  • The subjective nature of color suggests that perception is influenced by mental processes rather than solely physical properties.

• Qualities of Color

  • Hue: The color itself, determined by wavelength.
  • Brightness: The perceived intensity of light.
  • Saturation: The purity of the color, indicating how much gray is mixed with it.

• Trichromatic Theory of Color Vision

  • Proposes three primary cones in the retina (blue, green, red) that combine to allow perception of various colors.

• Opponent Process Theory of Color Vision

  • Suggests color perception is controlled by opposing processes (e.g., red-green, blue-yellow).
  • Evidence includes afterimages that occur when staring at a color for too long.

• Physiological Basis of Opponent Process Theory

  • Involves neural mechanisms in the retina and the brain that selectively respond to opposing colors.

• Color Vision Deficiency

  • Various forms include:
  • Protanopia: Red-deficient vision due to missing red cones.
  • Deuteranopia: Green-deficient vision due to missing green cones.
  • Causes can be genetics or damage to the visual pathways.

Perceiving Depth (Chapter 6)

• Absolute vs. Relative Distance

  • Absolute distance refers to a fixed measurement, while relative distance involves comparing distances between objects, crucial for depth perception.

• Oculomotor Cues

  • Involve eye movements such as convergence (inward turning) and accommodation (focusing distance) that aid 3D vision.

• Binocular Vision (Stereopsis)

  • Involves integrating images from both eyes to perceive depth through retinal disparity (the slight difference in images viewed by each eye).

• Neurobiological Basis of Stereoscopic Vision

  • Disparity-selective cells respond to differences in images from both eyes, aiding depth perception.

• Monocular Depth Cues

  • Cues that can be perceived with one eye, like size, texture gradient, and occlusion.

• Static Monocular Depth Cues

  • Include:
  1. Linear perspective: Lines converging suggest depth.
  2. Relative size: Objects that appear smaller are perceived as further away.
  3. Interposition: Overlapping objects indicate which is closer.

• Moon Illusion

  • The phenomenon where the moon appears larger on the horizon than overhead, potentially due to perceived distance distortions based on environmental context.

• Motion Parallax

  • As an observer moves, nearby objects appear to move faster than those further away, providing cues for depth perception.

• Depth Theory

  • Explains perceived size errors through size illusions like the Ames Room, where spatial relationships are distorted but perceived size remains consistent based on context.