Overview
This lecture explains the difference between sensation and perception, introduces thresholds in sensory detection, and discusses factors influencing perception such as attention, motivation, adaptation, and culture.
Sensation
- Sensory receptors are specialized neurons that respond to specific stimuli, resulting in sensation.
- Transduction is the process of converting sensory stimulus energy into action potentials sent to the central nervous system.
- Humans have more than five senses, including vestibular (balance), proprioception and kinesthesia (body position and movement), nociception (pain), and thermoception (temperature).
Sensory Thresholds
- Absolute threshold is the minimum stimulus energy needed to detect a stimulus 50% of the time.
- Subliminal messages are stimuli below the absolute threshold that are received but not consciously perceived.
- Difference threshold (just noticeable difference, jnd) is the smallest difference in stimulus intensity needed to detect a change.
- Weber’s law states the difference threshold is a constant fraction of the original stimulus intensity.
Perception
- Perception is the organization, interpretation, and conscious experience of sensory information.
- Bottom-up processing builds perceptions from sensory input; top-down processing uses knowledge, experiences, and thoughts.
- Sensation is a physical process; perception is psychological.
Influences on Perception
- Sensory adaptation is reduced sensitivity to a constant stimulus over time.
- Attention determines which sensory information is perceived.
- Inattentional blindness is failing to notice a visible stimulus due to focused attention elsewhere.
- Motivation can shift our ability to detect a stimulus among background noise (signal detection theory).
- Beliefs, values, expectations, and culture shape our perceptions (e.g., cultural differences in visual illusions).
Key Terms & Definitions
- Sensation — Detection of stimuli by sensory receptors and transmission of information to the brain.
- Transduction — Conversion of stimulus energy into neural signals.
- Absolute threshold — Minimum stimulus intensity detected 50% of the time.
- Subliminal message — Stimulus below conscious awareness.
- Difference threshold / JND — Minimum change in stimulus required to notice a difference.
- Weber’s law — The difference threshold is a constant proportion of the original stimulus.
- Perception — The process of organizing and interpreting sensory information.
- Bottom-up processing — Perception built from sensory input.
- Top-down processing — Perception influenced by experience and expectations.
- Sensory adaptation — Diminished sensitivity due to constant stimulation.
- Inattentional blindness — Failure to perceive visible objects when focused elsewhere.
- Signal detection theory — Detecting signals amid background noise.
Action Items / Next Steps
- Watch the linked selective attention test to observe inattentional blindness in action.
- Review cultural influences on perception and examples such as the Müller-Lyer illusion.