5.1 Sensation versus Perception

Sensation and perception work together to help us make sense of the world around us. Sensation involves detecting stimuli through our senses, while perception is about interpreting and organizing that information in our brains.

Our ability to detect and differentiate stimuli is influenced by thresholds, attention, motivation, and adaptation. These factors shape how we process sensory input and form coherent representations of our environment.

Sensation and Perception

Sensation vs perception

• Sensation involves detecting and encoding sensory stimuli from the environment through sensory receptors in the sensory organs (eyes, ears, nose, tongue, skin) and converting physical stimuli into electrical signals (neural impulses)
• Perception involves interpreting, organizing, and giving meaning to sensory information in the brain influenced by factors such as experience, learning, expectation, and attention allowing us to make sense of the sensory information and create a coherent representation of the world

Absolute and difference thresholds

• Absolute threshold represents the minimum amount of stimulus energy required to detect a stimulus 50% of the time varying depending on the sensory modality
  • Faintest light that can be detected in a dark room
  • Softest sound that can be heard in a quiet environment
• Difference threshold (Just Noticeable Difference, JND) represents the minimum amount of change in a stimulus required to detect a difference 50% of the time
  • Also known as Weber's Law: $JND = k × I$, where $k$ is a constant and $I$ is the initial stimulus intensity
  • Smallest difference in weight between two objects that can be detected
  • Minimal change in brightness required to notice a difference between two lights
• Signal detection theory explains how we distinguish between signal (presence of a stimulus) and noise (background information), influencing our perceptual decisions

Influences on perception

• Attention involves selectively focusing on specific aspects of sensory information while ignoring others allowing us to prioritize and process relevant information effectively
  • Focusing on a conversation in a crowded room (cocktail party effect)
  • Noticing a familiar face in a crowd
• Motivation acts as the driving force behind our behavior and perception influencing what we pay attention to and how we interpret sensory information
  • Being more likely to notice food-related cues when hungry
  • Interpreting ambiguous stimuli in a way that aligns with our goals or desires
• Sensory adaptation involves the decrease in sensitivity to a constant stimulus over time allowing us to focus on changes in the environment rather than constant, unchanging stimuli
  • Becoming less aware of a persistent odor after prolonged exposure
  • Adapting to the temperature of a room after being in it for a while

Perceptual Processing and Organization

• Bottom-up processing involves analyzing sensory information from basic features to more complex patterns
• Top-down processing uses prior knowledge and expectations to interpret sensory information
• Gestalt principles describe how we organize and group visual elements to perceive whole patterns
• Perceptual constancy allows us to maintain stable perceptions of objects despite changes in sensory input (e.g., size, shape, color)