Sensation and Perception I. Introduction • Sensation and perception are fundamental processes through which we experience the world around us. • Sensation refers to the initial detection of stimuli by sensory receptors, while perception involves the interpretation and organization of those sensations. II. Sensation • Definition of Sensation o Sensation is the process by which sensory receptors detect environmental stimuli and convert them into neural signals. • Types of Sensory Receptors o Different sensory receptors are specialized for different types of stimuli: ▪ Photoreceptors: Respond to light (vision). ▪ Mechanoreceptors: Respond to mechanical pressure or distortion (hearing, touch). • ▪ Chemoreceptors: Respond to chemical stimuli (taste, smell). ▪ Thermoreceptors: Respond to temperature changes (heat, cold). ▪ Nociceptors: Respond to pain stimuli. Thresholds of Sensation o Absolute Threshold: The minimum intensity of a stimulus that can be detected 50% of the time. o Difference Threshold (Just Noticeable Difference): The minimum difference between two stimuli required for detection 50% of the time, influenced by Weber's Law. III. Perception • Definition of Perception o Perception is the process by which the brain organizes, interprets, and consciously experiences sensory information. • Factors Influencing Perception o Top-Down Processing: Involves using existing knowledge and expectations to interpret sensory information. o Bottom-Up Processing: Involves constructing perceptions from individual pieces of sensory information. • Gestalt Principles of Perception o The brain organizes sensory input into meaningful wholes using principles such as: ▪ Figure-Ground: Distinguishing an object (figure) from its background (ground). ▪ Proximity: Objects close together are perceived as belonging together. ▪ Similarity: Similar objects are grouped together. ▪ Closure: The mind fills in gaps to create a complete image. IV. Visual Perception • The Eye and Visual Processing o Light enters the eye through the cornea, passes through the pupil, and is focused by the lens onto the retina, where photoreceptors (rods and cones) convert light into neural signals. o • The optic nerve carries these signals to the brain for processing. Color Perception o Color is perceived through the activation of different types of cones in the retina. o Theories of color vision include: ▪ Trichromatic Theory: Proposes three types of cones sensitive to red, green, and blue light. ▪ Opponent-Process Theory: Suggests that color perception is controlled by opposing neural processes (e.g., red vs. green, blue vs. yellow). V. Auditory Perception • The Ear and Sound Processing o Sound waves are collected by the outer ear, transmitted through the middle ear, and converted into neural signals in the cochlea of the inner ear. • Sound Localization o The brain uses differences in the timing and intensity of sounds reaching each ear to determine the location of a sound source. VI. Other Sensory Modalities • Taste and Smell (Gustation and Olfaction) o Taste is detected through taste buds on the tongue, which respond to five basic tastes: sweet, salty, sour, bitter, and umami. o Smell is processed through olfactory receptors in the nasal cavity, allowing for the detection of various scents. • Touch and Pain o Touch involves multiple sensory receptors that respond to pressure, temperature, and pain, providing essential information about the environment. VII. Conclusion • Sensation and perception are integral to how we interact with and understand our environment. • By studying these processes, psychologists can gain insight into human behavior and the ways in which perception can be influenced by various factors, including context and individual experiences.