Sensation and Perception Overview

Sensation and Perception

• Stimulus: Physical energy that triggers a response in a sense organ.
• Sensation: The reception of physical energy by the sense organ.
• Perception: The brain's interpretation, analysis, and integration of stimuli, occurring in sensory and visual areas of the brain.
• Stimulus Energy to Perception: Light, sound, smells etc, stimulate sensory receptors in eyes, ears, nose etc. This triggers neural impulses that are processed in different brain areas.

Brain and Perception

• Brain Specialization: Different brain areas are specialized for processing different senses.
• Visual Cortex Sub-regions: Even within a single area like the visual cortex, specialized sub-areas perform specific tasks.

Critical Role of Sensation and Perception

• Information Overload: The world provides an excess of information.
• Selective Processing: Our perceptual systems prioritize relevant and significant information to be processed.
• Examples: Visual perception illustrates how only a specific range of light wavelengths are processed.
• Sensory Processing Stages: Sensation—perception—cognition form a sequence, each stage involving interpretation, elaboration, and assumptions to generate perception from raw information.

Visual Perception

• Eye Structure: The retina is a thin layer of photoreceptor cells. The fovea contains cones—important for color vision in sufficient light—and rods—for black and white vision in dim light.
• Color Perception: The brain compares activity across the three cone types to determine color, not relying on a single cone's activity.
• Processing: The brain actively processes information, not just passively receiving it.
• Color Constancy: Our perception of objects' colors remains relatively consistent even under different lighting conditions.

Gestalt Psychology

• Holistic Perception: Gestalt psychologists emphasize the tendency to integrate information into meaningful wholes.
• Perception is More than the Sum of Parts: Perception involves more than simply combining individual sensory inputs.

Perceiving Depth

• Depth Perception: Our ability to perceive the world in 3D and determine object distances despite receiving a 2D image on the retina.
• Cognitive Processing: Depth perception requires internal cognitive processes to interpret the 2D retinal image.
• Cues for Depth Perception: Relative size, light and shadow, interposition (overlap), and texture are examples of cues used to derive depth perception.
• Size Constancy: Our understanding of constant size for objects despite changes in distance or apparent size, aiding depth perception.

Face Perception

• Importance of Faces: Faces play a crucial role in communication, revealing emotions, indicating identity, and facilitating eye contact.
• Early Face Preference: Infants show a preference for face-like stimuli early in development. Studies, notably by Valenza et al (1996) and Mondloch et al (1999), demonstrate this.
• Facial Expressions: Newborns can discriminate and imitate facial expressions, as evidenced by Field et al (1982).
• Eye Contact & Direction: Eye contact is important in face-to-face interactions; eye direction is a communicative cue.
• Face Expertise & Inversion Effect: Our experience with faces creates expertise in face recognition, and the inversion effect (difficulty recognizing inverted faces) underscores the crucial role of facial configurations. The study by Yin (1996) illustrated this.
• The Thatcher Effect (Thompson, 1980): Difficulty detecting distortions (like eyes or mouth inverted) in inverted faces, demonstrating that configural processing is important in face recognition.
• Bruce & Young (1986) Model of Face Recognition: This model proposes stages of face recognition, from structural encoding to personal identity and name generation.
• Prosopagnosia (Face Blindness): A condition characterized by severe difficulties in face recognition, often resulting from brain damage.