2.1 - Perception

Perception

• Perception: How we organize, interpret, and make sense of these sensory signals.

How We Process Sensory Information

• Bottom-Up Processing: Building perception from the smallest sensory details and working up to a complete picture. Example: Seeing individual dots and then recognizing them as a picture.

• Top-Down Processing: Using our existing knowledge, expectations, and context to interpret sensory information. Example: Reading a misspelled word but still understanding its meaning.

Perception: Making Sense of Sensations

• Visual Capture: The tendency for vision to dominate other senses. Example: Movie sound seems to come from the screen, not the speakers.

• Gestalt Psychology: The whole is greater than the sum of its parts. We organize sensory information into meaningful patterns and wholes.

• Figure-Ground: Organizing the visual field into objects (figures) that stand out from their surroundings (ground).

• Grouping: Our tendency to organize stimuli into groups based on

Gestalt Principles of Perceptual Organization

• Proximity: We group nearby figures together.

• Similarity: We group figures that are similar to each other.

• Continuity: We perceive smooth, continuous patterns rather than discontinuous ones.

• Connectedness: We see uniform and linked objects as a single unit.  

• Closure: We fill in gaps to create complete, whole objects.

Depth Perception: Seeing in 3D

• Definition: The ability to judge distance and see objects in three dimensions, even though the images on our retinas are two-dimensional.

• Visual Cliff Experiment (Gibson & Walk): Showed that infants (and young animals) have innate depth perception.

Types of Depth Cues

• Monocular Cues: Cues that can be perceived with one eye alone.

  • Interposition (Overlap): Closer objects block the view of objects farther away.

  • Linear Perspective: Parallel lines appear to converge with distance.

  • Relative Size: If two objects are similar in size, the one that appears smaller is perceived as farther away.

  • Relative Height: Objects higher in the visual field are perceived as farther away.

  • Texture Gradient: Objects with finer, less detailed texture are perceived as farther away.

• Binocular Cues: Cues that require both eyes.

  • Convergence: The eyes turn inward more to focus on closer objects.

  • Retinal Disparity: The brain compares slightly different images from each eye to calculate distance. The greater the disparity, the closer the object.

Perception: Movement, Constancy, and Interpretation

Movement Perception

• Stroboscopic Motion: The illusion of movement created by a series of rapidly changing still images. Example: Flipbooks or animated films.

• Phi Phenomenon: The illusion of movement created by flashing lights in a sequence. Example: Marquees or holiday lights.

Perceptual Constancy: We perceive objects as stable and unchanging even as sensory input (light, angle, distance) changes.

• Size Constancy: We perceive an object's size as constant even when its distance changes.

  • Illusions:

    • Muller-Lyer Illusion: Two lines of the same length appear different due to the direction of arrows at their ends.

    • Ponzo Illusion: Two horizontal lines of the same length appear different because of converging lines around them.

    • Ames Room: A distorted room that makes people appear to shrink or grow as they move across it.

Perceptual Interpretation

• Perceptual Adaptation: The ability to adjust to a changed sensory input, such as an inverted or distorted visual field.

• Perceptual Sets: Our expectations and experiences influence how we perceive the world.

• Schemas: Mental frameworks that organize our knowledge and influence how we interpret new information.

• Context Effects: The surrounding environment or situation can alter our perception of a stimulus.

  • Cultural Context: Culture can also shape how we perceive things.

Factors Influencing Perception

• Biological: Sensory processing, innate visual abilities, critical periods for development.

• Psychological: Attention, learned schemas, emotions, expectations.

• Social-Cultural: Cultural norms and beliefs, physical context.

Human Factors and Perception

• Human Factors Psychology: A field that focuses on how people and machines interact. These psychologists use their understanding of perception and behavior to design user-friendly products and technology.

• Extrasensory Perception (ESP): The controversial claim that some people can perceive information without using the normal senses.

  • Telepathy: Mind-to-mind communication.

  • Clairvoyance: Perceiving remote events (e.g., knowing a friend is in trouble).

  • Precognition: Predicting future events.

  • Psychokinesis: Moving objects with the mind.

• Sensory Deprivation: Reducing sensory input to a minimum. Research has shown that this can lead to altered states of consciousness and even hallucinations.

• Selective Attention: The ability to focus on specific sensory information while filtering out other stimuli. Example: Listening to your friend's voice in a noisy crowd.