Object Perception and Perceptual Organization Chapter 5

Object Perception and Perceptual Organization

Amodal completion: Perceptional system creates a hole from the pieces that it sees.

Factors Influencing Perception

• Various principles affect what we perceive as foreground vs background:

• Symmetry: Objects that are symmetrical are often perceived as the foreground.

• Convexity: Convex objects (bulging outward) are more likely to be seen as foreground objects than concave (indented) shapes.

• Area: Smaller areas are often perceived as background objects.

• Orientation: Objects with primary orientations of vertical or horizontal are typically perceived as the foreground.

• Meaning - stimuli that are seen as meaningful tend to be seen as the foreground (figure)

Foreground and Background

• The brain's ability to separate objects from their surroundings.

  • Example: distinguishing a chair from a body or drink.

  • Dynamic visual scenes where objects are partial or obstructed.

• Key Terms:

  • Foreground: the primary object of focus.

  • Background: elements that are less prominent behind the foreground.

  • Segregation: the process of distinguishing different elements in a scene.

Amodal Completion

• Definition: the perceptual system's ability to infer the existence of objects that are partially hidden.

  • Example: perceiving a vase versus faces in an optical illusion.

  • Requires mental reconstruction of complete objects.

• Illustrative Example: Amodal completion manifested in visual illusions where shapes assist in perceiving familiar objects.

Gestalt Principles of Figure-Ground Segregation

• Several principles that guide how we perceive objects in relation to the background:

  • Figure-Ground: prioritizing certain elements as figures and others as background.

  • Ambiguous Images: Images that can be perceived in multiple ways, such as the Dalmatian or the horse.

  • Example: The ambiguous Dalmatian—different perceptions based on focus and individual interpretation.

  • The need for visual context to interpret ambiguity in images.

Examples of Perception

• Dynamic Scenes: The ability to identify elements using prior knowledge.

  • Example: Identifying a horse and Native American figures within a winter scene.

  • Images capture top-down processing influenced by prior experience.

• Illusions: Complex tasks in revealing simpler or expected objects from obscured scenes.

  • The cow’s head in a seemingly abstract arrangement signifies reliance on recognition after an explanation.

The Role of Context and Precedence in Perception

• Ambiguity in images demands engagement in figure-ground segregation.

• Illustrative Tasks: Identifying various objects based on limited visual cues.

  • Indicates reliance on top-down processing in interpreting environmental aspects.

  • Examples highlight how familiarity and context lead to recognition and memory retrieval.

Gestalt Principles in Action

• Principles such as symmetry, convexity, and area guide perception:

  • Objects that are symmetrical tend to attract attention as potential figures.

  • Bulging (convexity) often leads to perceptions of living objects.

  • Visual biases: Smaller areas might be favored as figures in ambiguous contexts.

Gestalt Principles of Object Organization:

Subjective Contour -  a line that your mind sees

Similarity - objects that are similar in some way tend to be grouped together

Proximity ; objects close

Closure - objects that incomplete tend to be completed by the visual system

Pragnaz (simplicity) central gestalt law - given several possible interpretations of stimulus the perceptual system prefers the most simple interpretation.

Problems - describes but doesn’t explain! Thus it is difficult to predict ahead of time what people will see.

Heuristics vs. Algorithms in Perception

• Algorithm: A specific, structured approach that guarantees a solution (e.g., mathematical formulas).

• Heuristic: A method of problem-solving that provides a shortcut and may not guarantee a solution but is generally efficient (e.g., rules of thumb).

• Importance of understanding algorithms in programming, especially in debugging processes.

Biological Bases of Perception

• The sensitivity of visual perception is often rooted in biological and evolutionary history.

• Phylogenetic Memory: The idea that certain perceptions, such as fear responses to spiders or snakes, are innate and evolutionary.

• Ontogeny: Individual development, distinct from species evolution.

Object Organization and Contextual Understanding

• Discussion on how context impacts perception.

• The Necker cube and subjective contours: How the brain perceives lines and edges that may not be explicitly present in sensory input.

• Highlighting the role of top-down processing in shaping our perception based on prior knowledge.