Thresholds and Subliminal Perception

This page continues the discussion of sensory thresholds and introduces the concept of subliminal perception.

Definition: A difference threshold is the minimum difference between two stimuli required for detection 50% of the time, also known as a just noticeable difference (jnd).

The page explains Weber's law, which states that the difference threshold increases proportionally with the size of the stimulus.

Definition: Weber's law is the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage rather than a constant amount.

The text then explores the concept of subliminal perception:

Definition: Subliminal refers to stimuli that are below one's absolute threshold for conscious awareness.

Example: In experiments, flashing positive or negative images subliminally before showing a neutral picture can influence people's perception of the neutral image, making it seem happier or more negative.

The page discusses how subliminal stimuli can affect our perceptions and behaviors:

Definition: Priming is the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response.

Highlight: Much of our information processing occurs automatically, out of sight, off the radar screen of our conscious mind.

The text concludes by noting that while subliminal stimuli can be detected by brain scanning, their effects on behavior are typically subtle and limited.

Introduction to Sensation and Perception

This page introduces the fundamental concepts of sensation and perception in psychology. It explores the processes by which we receive and interpret sensory information from our environment.

Definition: Sensation is the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.

Definition: Perception is the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

The page also introduces two key information processing approaches:

1. Bottom-up processing: Analysis that begins with sensory receptors and works up to the brain's integration of sensory information.
2. Top-down processing: Information processing guided by higher-level mental processes, drawing on our experience and expectations.

Example: Top-down processing helps us interpret what our senses detect, such as recognizing a face in a complex visual scene.

The concept of selective attention is introduced, highlighting our limited capacity to consciously process information.

Highlight: Our five senses take in approximately 11 million bits of information per second, but we consciously process only about 40 bits.

Example: The "cocktail party effect" demonstrates selective attention, where we can focus on one voice among many while still detecting our name in unattended conversations.