Sensation & Perception: Foundations, Processes, and Applications

Topic 4: Sensation & Perception

Introduction

This topic explores the fundamental processes of sensation and perception, highlighting how we detect and interpret sensory information from our environment. Understanding these processes is essential for grasping how humans experience and make sense of the world.

Prosopagnosia: Dissociating Sensing and Perceiving

Definition and Features

• Prosopagnosia is a cognitive disorder characterized by the inability to recognize faces, despite having otherwise intact vision.

• Also known as face blindness.

• Individuals can see facial features but cannot integrate them into a recognizable whole.

• Demonstrates that sensation (detecting features) and perception (recognizing patterns) are distinct processes.

Example: A person with prosopagnosia may not recognize close family members by their faces but can identify them by voice or clothing.

Sensation & Perception: Definitions and Distinctions

Key Concepts

• Sensation: The process of detecting physical energy (stimuli) from the environment and encoding it as neural signals. Sensory organs involved include vision (eyes), hearing (ears), smell (nose), taste (tongue), touch (skin), balance (vestibular system), and body awareness (proprioception).

• Perception: The process of organizing, interpreting, and making sense of sensory information.

Example: Sensation is the detection of light by the eyes; perception is recognizing a face in that light.

Transduction: Converting Energy to Neural Signals

Process Overview

• Transduction is the conversion of one form of energy into another, specifically the transformation of physical stimuli into neural impulses.

• Three main steps:

  1. Receive sensory information via receptor cells.

  2. Transform the stimulation into neural impulses (action potentials).

  3. Deliver the neural information to the brain for processing.

The Multitasking Brain: Bottom-Up and Top-Down Processing

Types of Processing

• Bottom-up processing: Perception that starts with sensory input, building up to more complex perceptions. Data-driven.

• Top-down processing: Perception influenced by memory, expectations, and prior knowledge. Concept-driven.

Example: Reading a word with missing letters (top-down) versus identifying a new object by its features (bottom-up).

Sensory Adaptation

Definition and Function

• Sensory adaptation is the process by which sensory receptor cells become less responsive to unchanging stimuli over time.

• Allows organisms to focus on novel or changing stimuli, conserving energy and cognitive resources.

Example: Becoming unaware of the feeling of your clothes after wearing them for a while.

Psychophysics: Measuring Sensation

Thresholds

• Absolute threshold: The minimum intensity of a stimulus that can be detected 50% of the time.

• Examples:

  • Seeing a candle flame 48 km away on a clear night.

  • Detecting 1 tablespoon of sugar dissolved in 7.5 liters of water.

Subliminal Perception

Definition and Applications

• Subliminal perception refers to the detection of stimuli below the absolute threshold for conscious awareness.

• Research shows little evidence for practical effects on persuasion (e.g., self-help tapes).

Just Noticeable Difference (JND) / Difference Threshold

Definition and Weber's Law

• JND (Just Noticeable Difference): The smallest difference in stimulus intensity that a person can detect.

• Weber's Law: The JND is not a fixed amount but a constant proportion relative to the intensity of the initial stimulus.

Formula:

$\frac{\Delta I}{I} = k$

Where $\Delta I$ is the change in intensity, $I$ is the original intensity, and $k$ is a constant (Weber fraction).

Example: Detecting a 5 dB increase in sound when the original sound is 40 dB, but needing a 10 dB increase when the original is 80 dB.

JND & Marketing

Applications in Consumer Behavior

• Marketers use JND to ensure positive changes (e.g., improved product) are noticeable, while negative changes (e.g., reduced size) are not.

• Subtle changes help retain customers by keeping modifications below the threshold of detection.

Example: Changing the packaging design or product size just below the JND so consumers do not notice a reduction in quantity.