Human Perception: Disorders, Theories, and Constancy

Human Perception: Disorders and Mechanisms

Disorders of Perception

• Hallucinations: The perception of an object that does not exist, which the subject believes they see. These are misperceptions with no basis in reality. The subject cannot avoid them, and they become part of their life.
• Hallucinosis: The subject perceives an object that does not exist in reality but is able to recognize that it is not real.
• Pareidolia: The subject perceives distorted objects from reality through imagination. There are imaginative components in this pathology.
• Illusions: An object from reality is perceived in a distorted, garbled, or different way. These false perceptions are based on specific characteristics of the stimulus.
  • Geometric Illusions: Some aspects of a line appear distorted due to various factors.
  • Ambiguous Figures: Where the position of an object can be confused.
  • Fictions: Seeing something that is not truly there.

Mechanisms of Perception

Theories of Perception

• Associationism: Initially, sensations are perceived in isolation. Afterward, the brain associates these sensations with each other by summing individual elements to build a complete perception. (Associated with Locke and Hume)
• Gestalt Theory: When attempting to analyze a stimulus, there is a tendency to perceive it as a whole rather than breaking it down into parts.

  Gestalt Laws of Grouping

  • Law of Proximity: Stimuli that are similar and near each other tend to be grouped together.
  • Law of Similarity: Similar things are seen together as part of the same set.
  • Law of Continuity: Objects presenting continuity will be perceived as part of a unified whole.
  • Law of Closure: An open or cut stimulus tends to be perceived as closed or complete.
• Figure-Ground Perception: Perceptions are organized so there is always a figure that stands out against a background, and this relationship can often be reversed.
• Prägnanz (Law of Good Form): This is the tendency for perception to fill in what, in fact, remains unfinished, simplifying complex stimuli into the simplest possible form.
• Perceptual Constancy: While nothing remains constant (e.g., the size of objects varies with distance and perspective), our brain always perceives the same color and size. Everything on our retina changes in size, yet everything appears the same as always.
• Apparent Motion: When two visual stimuli are viewed with a certain interval, we perceive a connection or movement between them, even if not physically present.
• Cognitive Theory: People possess cognitive schemata that are engraved in memory from prior learning. Perception, therefore, is a constructive process influenced by these internal frameworks.