Thresholds in Sensory Systems

This page delves into the concept of thresholds in sensory systems, focusing on absolute thresholds and difference thresholds.

Definition: Absolute threshold is the minimum stimulation necessary to detect a particular light, sound, pressure, taste, or odor 50 percent of the time.

The page provides a table detailing the absolute thresholds for different senses:

Example: For vision, the absolute threshold is a candle flame viewed from about 30 miles away on a dark night.

Signal detection theory is introduced, which predicts when we will detect weak signals. This theory assumes there is no single absolute threshold, and detection depends on a person's experience, expectations, motivation, and alertness.

Vocabulary: Subliminal stimuli are those that cannot be consciously detected 50% of the time, falling below the absolute threshold.

The concept of difference thresholds, also known as just noticeable difference (jnd), is explained. Weber's law is introduced, stating that for an average person to perceive a difference, two stimuli must differ by a constant minimum percentage, not a constant amount.

Highlight: The exact percentage for Weber's law varies depending on the stimulus, making it a flexible principle applicable to various sensory experiences.

Basic Concepts of Sensation & Perception

This page introduces the fundamental concepts of sensation and perception, highlighting the differences between these two processes and their importance in understanding how we interact with our environment.

Definition: Sensation is the process in which sensory receptors detect sensory information, and the nervous system transmits that information to the brain. Perception is the process by which the brain organizes and interprets sensory information.

The page discusses two types of processing:

1. Bottom-up processing: Analysis with no preexisting knowledge
2. Top-down processing: Analysis drawn on experience and expectation

Highlight: Selective attention plays a crucial role in how we perceive our environment. Our consciousness focuses on one thing at a time, which can lead to inattentional blindness and change blindness.

Example: In an experiment, viewers focused on counting basketball passes often failed to notice a woman with an umbrella walking across the screen, demonstrating inattentional blindness.

The concept of sensory transduction in psychology is introduced as the process of converting one form of energy into another that our brain can use. This process involves specialized receptor cells that receive stimuli, transform them into neural impulses, and deliver this information to the brain.

Vocabulary: Transduction can be thought of as translation or transformation of sensory information.