Psychology: Perception and Sensation

• Psychology is the scientific study of the mind and behavior
• It encompasses various subfields, including perception, cognition, emotion, personality, and social behavior
• Perception involves the way we organize and interpret sensory information to understand our environment
• It's a cognitive process that allows us to take in information through our senses (sight, sound, smell, taste, touch) and use it to experience the world around us

Sensation vs. Perception

• Sensation refers to the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment
• Perception involves organizing and interpreting this sensory information, enabling us to recognize meaningful objects and events
• Sensation is the raw data, while perception is the interpretation of that data

Bottom-Up Processing

• Bottom-up processing starts with sensory input and builds up to a final perception
• It emphasizes the role of the stimulus in shaping our experience
• Also known as data-driven processing

Top-Down Processing

• Top-down processing uses prior knowledge, expectations, and context to interpret sensory information
• It influences how we perceive the world based on previous experiences and beliefs
• Also known as conceptually driven processing

Perceptual Organization

• Perceptual organization refers to the way our brains group sensory information into meaningful patterns and forms
• Gestalt psychology principles describe how we tend to organize sensory input
• Key principles include:
  • Figure-ground relationship: We distinguish objects (figures) from their background (ground)
  • Proximity: We group nearby objects together
  • Similarity: We group similar objects together
  • Closure: We fill in gaps to create a complete, whole object
  • Continuity: We perceive continuous patterns rather than discontinuous ones
  • Common fate: We group together elements that appear to move in the same direction
  • Symmetry: We tend to perceive objects as symmetrical shapes that form around their center
  • Parallelism: We tend to perceive objects as being part of a whole when they are parallel to each other

Depth Perception

• Depth perception is the ability to perceive the world in three dimensions (3D) and to judge distances
• It relies on various cues, including:
  • Binocular cues: Rely on the use of both eyes
    • Retinal disparity: The difference in the images seen by the left and right eyes; the greater the disparity, the closer the object
    • Convergence: The extent to which the eyes turn inward when looking at an object; the more the eyes converge, the closer the object
  • Monocular cues: Available to each eye separately
    • Relative size: Smaller objects are perceived as farther away
    • Interposition: Objects that block other objects are perceived as closer
    • Relative clarity: Hazy objects are perceived as farther away
    • Texture gradient: Objects with finer texture are perceived as farther away
    • Relative height: Objects higher in the visual field are perceived as farther away
    • Linear perspective: Parallel lines converge in the distance
    • Light and shadow: Shading creates a sense of depth

Perceptual Constancy

• Perceptual constancy refers to the ability to perceive objects as stable and unchanging despite changes in sensory input
• Includes size constancy, shape constancy, and color constancy
  • Size constancy: Perceiving objects as having a constant size, even when their distance varies
  • Shape constancy: Perceiving objects as having a constant shape, even when viewed from different angles
  • Color constancy: Perceiving objects as having a constant color, even when lighting conditions change

Perceptual Adaptation

• Perceptual adaptation is the ability to adjust to altered sensory input
• For example, wearing glasses that distort vision initially causes disorientation, but eventually the brain adapts and vision returns to normal

Perceptual Set

• A perceptual set involves a mental predisposition to perceive something in a particular way
• It is influenced by expectations, experiences, context, and emotions
• Can affect how we interpret ambiguous stimuli

Attention and Perception

• Attention is the process of focusing awareness on a particular stimulus
• Selective attention allows us to focus on one stimulus while filtering out others
• Inattentional blindness is the failure to notice a visible object when our attention is directed elsewhere
• Change blindness is the failure to notice changes in the environment

Illusions

• Illusions are distortions of perception, where what we perceive does not match the physical reality
• They can provide insights into how the brain processes sensory information and constructs our perceptions

Factors Influencing Perception

• Culture: Cultural experiences can influence how we perceive the world
• Motivation: Our needs and desires can influence our perception
• Emotions: Our emotional state can influence how we interpret sensory information
• Expectations: Our prior beliefs and expectations can shape our perception