Overview
This lecture introduces the concepts of attention, sensation, and perception, focusing on how we select and interpret sensory input. Key topics include types of attention, factors affecting attention, perceptual organization, depth perception, perceptual constancy, illusions, and extrasensory perception.
Attention: Nature and Types
- Attention is the process of focusing on certain stimuli while ignoring others.
- Functions of attention: alerting, selective focus, limited capacity, and vigilance (sustained attention).
- Selective attention involves focusing on specific stimuli among many, e.g., listening to a teacher amid noise.
- Cocktail party effect: focusing on a specific voice amidst background noise.
- Sustained attention (vigilance) is maintaining focus over time, as in air traffic control.
Factors Influencing Attention
- External (physical) factors: movement, intensity, novelty, size, change, repetition, clarity, color, and contrast.
- Internal (psychological) factors: need, interest, and emotional state.
Sensation and Perception
- Sensation: activation of sense organs by environmental stimuli.
- Perception: organization, interpretation, and meaning given to sensory input.
- Transduction: conversion of sensory stimulus to neural energy.
- Perception is constructive, influenced by past experiences and needs.
Laws and Principles of Perceptual Organization
- Gestalt psychologists identified laws explaining how we organize sensory information into meaningful wholes.
- Key Gestalt principles: proximity, similarity, continuity, symmetry, closure, and figure-ground segregation.
Depth Perception
- Depth perception: ability to view the world in three dimensions.
- Monocular (one eye) cues: relative size, interposition, linear perspective, aerial perspective, light and shade, relative height, texture gradient, motion parallax.
- Binocular (both eyes) cues: retinal disparity, convergence, accommodation.
Perceptual Constancy
- Perceptual constancy: perception of objects as stable despite changes in sensory input.
- Types: size constancy, shape constancy, and brightness constancy.
Illusions
- Illusions: misperceptions due to incorrect interpretation of sensory information.
- Universal illusions: experienced by everyone (e.g., Muller-Lyer, Ponzo).
- Personal illusions: vary across individuals.
- Phi phenomenon: perception of motion from still images (e.g., movies).
Extrasensory Perception (ESP)
- ESP: perception without the use of known senses (telepathy, clairvoyance, precognition).
- Most psychologists reject ESP due to lack of scientific evidence.
Key Terms & Definitions
- Attention — Focusing cognitive resources on specific stimuli.
- Selective Attention — Concentrating on particular stimuli.
- Sustained Attention — Prolonged focus on a stimulus or task.
- Perception — Interpreting and organizing sensory input.
- Transduction — Converting physical stimuli into neural signals.
- Gestalt Laws — Principles explaining perceptual organization.
- Depth Perception — Ability to judge distance and three-dimensionality.
- Perceptual Constancy — Stability of perceptions despite changing sensory input.
- Illusion — False perception or misinterpretation of sensory information.
- ESP — Extrasensory perception; perceiving information without the normal senses.
Action Items / Next Steps
- Review and distinguish selective vs. sustained attention.
- List and explain the Gestalt laws of perceptual organization.
- Practice identifying monocular and binocular depth cues in real life.
- Draw examples of perceptual illusions discussed.
- Prepare answers for the terminal questions for revision.